ELONGATED HYPOCOTYL5 （HY5）, a member of the bZlP transcription factor family, inhibits hypocotyl growth and lateral root development, and promotes pigment accumulation in a light-dependent manner in Arabidopsis. Rec...ELONGATED HYPOCOTYL5 （HY5）, a member of the bZlP transcription factor family, inhibits hypocotyl growth and lateral root development, and promotes pigment accumulation in a light-dependent manner in Arabidopsis. Recent research on its role in different processes such as hormone, nutrient, abiotlc stress （abscisic acid, salt, cold）, and reactive oxygen species signaling pathways clearly places HY5 at the center of a transcriptional network hub. HY5 regulates the transcription of a large number of genes by directly binding to cis-regulatory elements. Recently, HY5 has also been shown to activate its own expression under beth visible and UV-B light. Moreover, HY5 acts as a signal that moves from shoot to root to promote nitrate uptake and root growth. Here, we review recent advances on HY5 research in diverse aspects of plant development and highlight still open questions that need to be addressed in the near future for a complete understanding of its function in plant signaling and beyond.展开更多
In etiolated seedlings, light perceived by phytochrome promotes the expression of light-harvesting chlorophyll a/b protein of photosystem Ⅱ （Lhcb） genes. However, excess of photosynthetically active radiation can r...In etiolated seedlings, light perceived by phytochrome promotes the expression of light-harvesting chlorophyll a/b protein of photosystem Ⅱ （Lhcb） genes. However, excess of photosynthetically active radiation can reduce Lhcb expression. Here, we investigate the convergence and divergence of phytochrome, high-light stress and abscisic acid （ABA） signaling, which could connect these processes. Etiolated Arabidopsis thaliana seedlings bearing an Lhcb promoter fused to a reporter were exposed to continuous far-red light to activate phytochrome and not photosynthesis, and treated with ABA. We identified a cis-acting region of the promoter required for down-regulation by ABA. This region contains a CCAC sequence recently found to be necessary for ABI4-binding to an Lhcb promoter. However, we did not find a G-box-binding core motif often associated with the ABI4-binding site in genes promoted by light and repressed by ABI4. Mutations involving this motif also impaired the responses to reduced water potential, the response to high photosynthetic light and the response to methyl viologen but not the response to low temperature or to Norflurazon. We propose a model based on current and previous findings, in which hydrogen peroxide produced in the chloroplasts under high light conditions inter- acts with the ABA signaling network to regulate Lhcb expression. Since the mutation that affects high-light and methyl viologen responses does not affect phytochrome-mediated responses, the regulation by retrograde and phytochrome signaling can finally be separated at the target promoter level.展开更多
我们回顾了目前关于土壤生物多样性及其在生态系统过程中的作用、对于人类目标的重要性及对胁迫和扰动的恢复能力等的研究进展。现存物种的数量远远大于人们已经描述的数量,即使是对于肉眼可见的分类群也是如此。而且也普遍缺乏在生物...我们回顾了目前关于土壤生物多样性及其在生态系统过程中的作用、对于人类目标的重要性及对胁迫和扰动的恢复能力等的研究进展。现存物种的数量远远大于人们已经描述的数量,即使是对于肉眼可见的分类群也是如此。而且也普遍缺乏在生物地理学上的综合描述。迫切需要在分类学和对新一代系统科学家培训上做更大努力。尤其是应当集中致力于就我们所知。对生态系统功能起关键作用的土壤生物类群方面。为了确定这种类群,需要对土壤生物区系的影响圈(sphere of Influence,SOI),如根的生物区系、有机物质破碎者(shredder)和土壤生物扰动者(bioturbator)加以识别,这些影响圈比如可能通过与植物的相互作用而控制着生态系统的过程。在这些SOI中,我们分析出了土壤有机体的功能类群。最迫切需要研究的问题是将物种按功能类群进行区分,并确定功能类群中的物种冗余。这种迫切性是根据为阐述与集约化农业、森林扰动、环境污染和全球环境变化有关的土壤功能丧失程度的需要而确定的。目前认为最处于危险的土壤生物区系是那些大型动物群的有机物破碎者、土壤生物扰动者、某些专门的细菌(如硝化细菌和固氮菌)以及形成真菌的菌根中贫乏物种的功能类群。在开展这些优先性研究时,需要使用长期的和大尺度的田间试验,以及地理统计学和地理信息系统等现代方法进行试验研究。展开更多
Plants detect and respond to the proximity of competitors using light signals perceived by photoreceptor proteins.A low ratio of red to far-red radiation(R:FR ratio)is a key signal of competition that is sensed by the...Plants detect and respond to the proximity of competitors using light signals perceived by photoreceptor proteins.A low ratio of red to far-red radiation(R:FR ratio)is a key signal of competition that is sensed by the photoreceptor phytochrome B(phyB).Low R:FR ratios increase the synthesis of growth-related hormones,including auxin and gibberellins,promoting stem elongation and other shade-avoidance responses.Other photoreceptors that help plants to optimize their developmental configuration and resource allocation patterns in the canopy include blue light photoreceptors,such as cryptochromes and phototropins,and UV receptors,such as UVR8.All photoreceptors act by directly or indirectly controlling the activity of two major regulatory nodes for growth and development:the COP1/SPA ubiquitin E3 ligase complex and the PIF transcription factors.phyB is also an important modulator of hormonal pathways that regulate plant defense against herbivores and pathogens,including the jasmonic acid signaling pathway,In this Perspective,we discuss recent advances on the studies of the mechanisms that link photoreceptors with growth and defense.Understanding these mechanisms is important to provide a functional platform for breeding programs aimed at improving plant productivity,stress tolerance,and crop health in species of agronomic interest,and to manipulate the light environments in protected agriculture.展开更多
In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling down...In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling downstream of PIF1/PIL5, the signaling network inducing germination by phyA is poorly known. Here, we describe the influence of phyA on the transcriptome of Arabidopsis seeds when germination is induced by a far-red （FR） pulse. The expression of 11% of the genome was significantly regulated by phyA. Most of the genes were up-regulated and the changes noted late （i.e. 5 h after a FR pulse）, whereas changes in down-regulated genes were more abundant earlier （i.e. 0.5 h after a FR pulse）. Auxin- and GA-associated elements were overrepresented in the genes that were modified by phyA. A significant number of genes whose expression was affected by phyA had not been previously reported to be dependent on PIL5. Among them, homozygotic mutant seeds of MYB66, a SAUR-like protein, PIN7, and GASA4 showed an impaired promo- tion of germination by phyA. Natural variation at the transcriptional level was found in early signaling and GA metabolic genes, but not in ABA metabolic and expansin genes between Columbia and Landsberg erecta accessions. Although phyA and phyB/PIL5 signaling pathways share some molecular components, our data suggest that phyA signaling is partially independent of PIL5 when germination is promoted by very low fluences of light.展开更多
We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana. Afternoon shade events promoted hypocotyl growth, while morning shade was ineffect...We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana. Afternoon shade events promoted hypocotyl growth, while morning shade was ineffective. The Ihy-D, elf3, lux, pif4 pifS, tocl, and quadruple della mutants retained the response to afternoon shade and the lack of response to morning shade while the Ihyccal mutant responded to both morning and afternoon shade. ThephyB mutant, plants overexpressing the multidrug resistance-like membrane protein ABCB19, and the iaa17/axr3 loss-of-function mutant failed to respond to shade. Transient exposure of sunlight-grown seedlings to synthetic auxin in the afternoon caused a stronger promotion of hypocotyl growth than morning treatments. The promotion of hypocotyl growth by afternoon shade or afternoon auxin required light perceived by phytochrome A or cryptochromes during the previous hours of the photoperiod. Although the ELF4-ELF3-LUX complex, PIF4, PIF5, and DELLA are key players in the generation of diurnal hypocotyl-growth patterns, they exert a minor role in the control of the diurnal pattern of growth responses to shade. We conclude that the strong diurnal dependency of hypocotyl-growth responses to shade relates to the balance between the antagonistic actions of LHY-CCA1 and a light-derived signal.展开更多
Reactive oxygen species are in all types of organisms from microbes to higher plants and animals.They are by-products of normal metabolism,such as photosynthesis and respiration,and are responsive to abiotic and bioti...Reactive oxygen species are in all types of organisms from microbes to higher plants and animals.They are by-products of normal metabolism,such as photosynthesis and respiration,and are responsive to abiotic and biotic stress.Accumulating evidence suggests reactive oxygen species play a vital role in programmed cell death,stress responses,plant defense against pathogens and systemic stress signaling in conjunction with antioxidant production.Here,we propose that reactive oxygen species and antioxidants,as both universal and evolutionarily conserved,are likely to play important role(s)in symbiotic interactions.To support this hypothesis we review the root and foliar fungal endophyte literature specific to fungal-plant symbiotum production of reactive oxygen species and antioxidants in response to stress.These asymptomatic fungi can produce antioxidants in response to both biotic and abiotic stress when grown in culture as well as in planta.In addition,there is a growing but nascent literature reporting a significant impact of endophyte colonization on the antioxidant activity of colonized(E+)hosts when compared to uncolonized(E-)hosts,especially when exposed to stress.Here we summarize general patterns emerging from the growing literature specific to antioxidant activity of endophytes in colonized hosts and bring up possible future research questions and approaches.The consequences of changes in reactive oxygen species production and increased antioxidant activity in the symbiotum appear to be beneficial in many instances;but costs are also indicated.Unexplored questions are:1)to what extent do antioxidants originating from the fungal endophyte mediate host metabolism,and thereby control host responses to endophyte colonization;(2)what role do fungal,plant,or symbiotum produced reactive oxygen species and antioxidants have in determining symbiotic outcome between extremes of pathogenicity and mutualism;and(3)what role if any,do the production of reactive oxygen species and their antioxidant counterparts play in th展开更多
Seed dormancy is a developmental checkpoint that prevents mature seeds from germinating under conditions that are otherwise favorable for germination.Temperature and light are themost relevant environmental factors th...Seed dormancy is a developmental checkpoint that prevents mature seeds from germinating under conditions that are otherwise favorable for germination.Temperature and light are themost relevant environmental factors that regulate seed dormancy and germination.These environmental cues can trigger molecular and physiological responses including hormone signaling,particularly that of abscisic acid and gibberellin.The balance between the content and sensitivity of these hormones is the key to the regulation of seed dormancy.Temperature and light tightly regulate the transcription of thousands of genes,as well as other aspects of gene expression such asmRNAsplicing,translation,and stability.Chromatin remodeling determines specific transcriptional outputs,and alternative splicing leads to different outcomes and produces transcripts that encode proteins with altered or lost functions.Proper regulation of chromatin remodeling and alternative splicing may be highly relevant to seed germination.Moreover,microRNAs are also critical for the control of gene expression in seeds.This review aims to discuss recent updates on post-transcriptional regulation during seed maturation,dormancy,germination,and post-germination events.We propose future prospects for understanding howdifferent post-transcriptional processes in crop seeds can contribute to the design of genotypes with better performance and higher productivity.展开更多
Early detection of infected asymptomatic plants could prevent the dissemination of tomatobacterial canker throughout the crop and, thus, reduce associated economic losses. Reflectance spectroscopy has been proposed fo...Early detection of infected asymptomatic plants could prevent the dissemination of tomatobacterial canker throughout the crop and, thus, reduce associated economic losses. Reflectance spectroscopy has been proposed for the detection of diseases in plants, mainlycaused by foliar fungal pathogens. In contrast, bacterial canker is a vascular disease thatdoes not produce visible foliar symptoms until it is too late to avoid contagion to otherplants. The effects of the disease on the conductivity of the xylem have an impact onthe water content of the leaves;initially, a subtle effect that cannot be assessed with thenaked eye but can be evaluated by reflectance spectroscopy. The objective of this workwas to identify indices, based on the reflectance spectral signature of the plants, for thedetection of tomato plants affected by bacterial canker prior to the appearance of symptoms. To verify that the proposed methodology is applicable to a broad range of tomatogenotypes, two experiments were carried out with different tomato cultivars grown in potsand another on the ground in a greenhouse. Plants were inoculated with the pathogenicbacteria and the reflectance spectrum of the apical leaflet of two leaves per plant wereobtained before symptoms expression;several spectral indices were calculated from thereflectance spectra. Three indices, of the shortwave-infrared zone, allowed the detectionof bacterial canker inoculated plants in a fast and non-destructive way, up to one weekbefore symptoms were visible: Normalized Difference Water Index (NDWI), Simple Ratioof Water Index (SRWI) and Water Index 1 180 (WI1180). Our research demonstrates, forthe first time, the usefulness of spectral indices sensitive to water content for the identifi-cation of diseased plants. These indices arise as a promising tool for the early detection ofvascular plant diseases, that could be integrated into sustainable management plans.展开更多
The Rio de la Plata region comprises central Argentina,Uruguay,and southern Brazil.Modern agriculture developed around 1900 with recent decades being characterized by the advance of cropping areas over native grasslan...The Rio de la Plata region comprises central Argentina,Uruguay,and southern Brazil.Modern agriculture developed around 1900 with recent decades being characterized by the advance of cropping areas over native grasslands.Highly specialized agriculture has decoupled crop and livestock production but has succeeded in intensifying yields.However,significant losses of ecosystem services have been reported.Thus,questions have been raised on the sustainability of this pathway.A glance at world regions that have experienced similar trends suggests that an urgent course correction is needed.A major concern has been the lack of diversity in regions with highly specialized agriculture,promoting renewed interest in integrated crop-livestock systems(ICLS),not only because ICLS are more diverse than specialized systems,but also because they are rare examples of reconciliation between agroecosystem intensification and environmental quality.Consequently,this paper discusses alternatives to redesign multifunctional landscapes based on ICLS.Recent data provide evidence that recoupling crop and animal production increases the resilience of nutrient cycling functions and economic indicators to external stressors,enabling these systems to face climate-market uncertainty and reconcile food production with the provision of diverse ecosystem services.Finally,these concepts are exemplified in case studies where this perspective has been successfully applied.展开更多
Aims In arid communities,it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbour-ing bare ground areas.This becomes relevant in systems where the vegetation is distri...Aims In arid communities,it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbour-ing bare ground areas.This becomes relevant in systems where the vegetation is distributed in patches surrounded by bare soil.However,whether roots of different species may be overlapping under bare ground areas is still controversial.The factors control-ling root responses when no plants appear to be directly influ-encing the gap among patches are still unclear.The aim of our study was to detect perennial grasses responses to an N enrich-ment pulse.Methods In a semi-arid steppe(Patagonia,Argentina),we buried root traps filled with sieved soil with and without N addition,under bare soil patches.Traps were harvested after 4 and 6 months.Trap neighbour-hoods(30 cm in diameter)included at least three of the dominant tussock species.After harvests,we identified species in the traps by root traits and quantified diversity,biomass and specific relative growth rates.Important Findings Bare ground areas show simultaneous root growth of different spe-cies.Diversity of perennial grass roots was higher with N addition than without it in the first harvest(4 months),but this difference disappeared in the second harvest(6 months).Root biomass was maximal after 6 months in N addition traps.Species preferred by herbivores(Bromus pictus and Poa ligularis)showed rapid growth and responses to N addition.Differences between harvests may be an indicative that N pulses interact with rising temperatures and soil water content as growing season progress.展开更多
Fungal endophytes are suggested to manipulate host grass reproduction.Using different grass-endophyte combinations in a four year common garden experiment,we show that endophyte can retain control over the reproductiv...Fungal endophytes are suggested to manipulate host grass reproduction.Using different grass-endophyte combinations in a four year common garden experiment,we show that endophyte can retain control over the reproductive functions of the host.Plants were collected as seeds from two different environments,meadows and riverbanks.Natural endophyte infection(E+)increased reproductive effort of plants;13 and 15%higher proportion of E+plants produced panicles compared to naturally uninfected(E-)and manipulatively endophyte-infected(ME+)plants,respectively.Meadoworigin E+plants produced also higher number of panicles compared to E-in the last two years,and both meadow-and riverbank-origin ME+plants produced higher number of panicles compared to ME-plants in most of the years.Pseudovivipary was recorded in 5%of the plants each year.Pollen limitation appears not to induce pseudovivipary.Both E+and ME+plants produced higher number of seminiferous panicles compared to E-and ME-plants.The higher proportion of pseudoviviparism in ME+plants compared to E+,Eand ME-plants from meadows suggests specific genotypegenotype cross-talk between endophyte and grass.Pseudovivipary was affected by year and primarily explained by plant reproductive effort since most vigorous plants produced more pseudoviviparous panicles.We propose that endophytes can promote host grass reproduction in a habitatspecific manner and depending on genetic compatibility between partners.However,reproductive behavior depended on maternal habitat and the annual environmental conditions highlighting the importance of long-term experiments to estimate the effects of endophytes on host plant ecology.展开更多
Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions.Epichloae fungal endophytes associat...Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions.Epichloae fungal endophytes associate with cool-season grasses,growing systemically within the plant inter-cellular spaces and are transmitted through seeds.We explore the endophytes influence on the relationship between the plant reproductive and vegetative aboveground biomass(reproductive effort:RE)and on the trade-off between two components of the reproductive biomass,number and weight of panicles(RPN),using tall fescue as a model system.Naturally endophyte-colonized,manipulatively endophyte-free,and naturally endophyte-free plants from Northern European wild-populations together with the cultivar Kentucky-31 were grown under different environmental conditions(nutrients x water).The endophyte had an effect on the RPN(E+:6.19,ME-:4.68 and E-:4.40)which indicates how reproductive biomass is partitioned into number and mass of panicles,but not on RE(≈0.06).As expected,wild plants showed higher reproductive effort(≈0.06)compared to the cultivar KY-31(0.05),irrespective of endophyte presence.Endophyte-colonized plants had lighter panicles than endophyte-free plants,a pattern that was clear among low-yielding plants.Similarly,the tradeoff between RPN and RE was higher for endophytecolonized plants.This was again evident among plants with low RE indicating that colonized plants split the yield into either greater number of panicles and/or lighter panicles.The effect of vertically transmitted endophytes has earlier been studied as ratios(e.g.RE);however,our study shows that this approach may hide size-dependent endophyte effects on these relationships.Our study reveals that Neotyphodium endophyte affects trade-offs in tall fescue plants in a complex manner,and is influenced by a number of biological and abiotic factors.展开更多
Pooideae grasses may be colonized by systemic fungal endophytes.The fitness of endophyte depends entirely on resources and seed transmission from the host plant,while colonized plants may gain increased survival,growt...Pooideae grasses may be colonized by systemic fungal endophytes.The fitness of endophyte depends entirely on resources and seed transmission from the host plant,while colonized plants may gain increased survival,growth,and reproduction relative to their uncolonized conspecifics.Most research of endophyte-grass interactions have been carried out on few cultivars of tall fescue(Schedonorus phoenix)and their symbiont Neotyphodium coenophialum.Lack of studies using wild populations of tall fescue across the species natural distribution range,however,limits the understanding of the ecological and evolutionary role of the symbiosis in nature.We performed a common garden experiment in Southern Finland with three wild,tall fescue populations from northern Europe and the forage cultivar Kentucky-31(KY-31).For each population,we used naturally endophyte-colonized,naturally endophytecolonized but endophyte removed(decolonized),and naturally uncolonized plants to separate effects due to the host genotype from the endophyte.We evaluated growth variables and survival in four environmental treatments of varying water and nutrients.Supply of water and nutrients increased plant biomass and reproductive effort in all populations.This effect was higher for KY-31 plants which produced on average 55%more seeds than wild plants,indicating better adaptation to high resource environments.However,the higher incidence of Claviceps sp.and the low winter survival indicated KY-31 tall fescue is mal-adapted to Northern European conditions.Naturally colonized plants had greater plant biomass(≈12%),reproductive effort(≈22%)and seed mass(≈29%)than naturally uncolonized and decolonized plants.Nonetheless,endophyte colonization did not affect plant survival,and the effects of endophyte colonization on tiller number,panicle/tiller ratio and Claviceps sp.incidence depended on the population origin.In the wild populations,endophyte removal only reduced the number of tillers(≈29%lower),while the difference between naturally colonized and natur展开更多
Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presen...Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presence of E.festucae could affect the infection of a plant by other fungal species.This could occur if E.festucae metabolites produced in planta interfere negatively with other fungal infections;or alternatively,if the modulation of plant defenses by the endophyte favour further fungal infections.We have analyzed the presence of culturable non-systemic endophytes in plants of F.rubra infected(E+)and not infected(E−)by E.festucae in two subarctic habitats,meadows and riverbanks in Northern Finland.The observed non-systemic endophyte infection frequencies were similar among E+and E−plants from riverbanks,and E+plants from meadows.In contrast to these,the infection frequency was significantly lower in E−plants from meadows.This result suggests that the presence of E.festucae is not a main factor determining the presence of non-systemic endophytes in plants.Instead,plant genetic characteristics related to compatibility with E.festucae and other endophytes in the more stable meadow populations might play a role in these fungus–fungus–plant interactions.As a result of the survey,18 different taxa of non-systemic endophytes were identified in plants of F.rubra.All were ascomycetes except for one basidiomycete.Three endophytic taxa could not be ascribed to a genus,but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.展开更多
文摘ELONGATED HYPOCOTYL5 （HY5）, a member of the bZlP transcription factor family, inhibits hypocotyl growth and lateral root development, and promotes pigment accumulation in a light-dependent manner in Arabidopsis. Recent research on its role in different processes such as hormone, nutrient, abiotlc stress （abscisic acid, salt, cold）, and reactive oxygen species signaling pathways clearly places HY5 at the center of a transcriptional network hub. HY5 regulates the transcription of a large number of genes by directly binding to cis-regulatory elements. Recently, HY5 has also been shown to activate its own expression under beth visible and UV-B light. Moreover, HY5 acts as a signal that moves from shoot to root to promote nitrate uptake and root growth. Here, we review recent advances on HY5 research in diverse aspects of plant development and highlight still open questions that need to be addressed in the near future for a complete understanding of its function in plant signaling and beyond.
文摘In etiolated seedlings, light perceived by phytochrome promotes the expression of light-harvesting chlorophyll a/b protein of photosystem Ⅱ （Lhcb） genes. However, excess of photosynthetically active radiation can reduce Lhcb expression. Here, we investigate the convergence and divergence of phytochrome, high-light stress and abscisic acid （ABA） signaling, which could connect these processes. Etiolated Arabidopsis thaliana seedlings bearing an Lhcb promoter fused to a reporter were exposed to continuous far-red light to activate phytochrome and not photosynthesis, and treated with ABA. We identified a cis-acting region of the promoter required for down-regulation by ABA. This region contains a CCAC sequence recently found to be necessary for ABI4-binding to an Lhcb promoter. However, we did not find a G-box-binding core motif often associated with the ABI4-binding site in genes promoted by light and repressed by ABI4. Mutations involving this motif also impaired the responses to reduced water potential, the response to high photosynthetic light and the response to methyl viologen but not the response to low temperature or to Norflurazon. We propose a model based on current and previous findings, in which hydrogen peroxide produced in the chloroplasts under high light conditions inter- acts with the ABA signaling network to regulate Lhcb expression. Since the mutation that affects high-light and methyl viologen responses does not affect phytochrome-mediated responses, the regulation by retrograde and phytochrome signaling can finally be separated at the target promoter level.
文摘我们回顾了目前关于土壤生物多样性及其在生态系统过程中的作用、对于人类目标的重要性及对胁迫和扰动的恢复能力等的研究进展。现存物种的数量远远大于人们已经描述的数量,即使是对于肉眼可见的分类群也是如此。而且也普遍缺乏在生物地理学上的综合描述。迫切需要在分类学和对新一代系统科学家培训上做更大努力。尤其是应当集中致力于就我们所知。对生态系统功能起关键作用的土壤生物类群方面。为了确定这种类群,需要对土壤生物区系的影响圈(sphere of Influence,SOI),如根的生物区系、有机物质破碎者(shredder)和土壤生物扰动者(bioturbator)加以识别,这些影响圈比如可能通过与植物的相互作用而控制着生态系统的过程。在这些SOI中,我们分析出了土壤有机体的功能类群。最迫切需要研究的问题是将物种按功能类群进行区分,并确定功能类群中的物种冗余。这种迫切性是根据为阐述与集约化农业、森林扰动、环境污染和全球环境变化有关的土壤功能丧失程度的需要而确定的。目前认为最处于危险的土壤生物区系是那些大型动物群的有机物破碎者、土壤生物扰动者、某些专门的细菌(如硝化细菌和固氮菌)以及形成真菌的菌根中贫乏物种的功能类群。在开展这些优先性研究时,需要使用长期的和大尺度的田间试验,以及地理统计学和地理信息系统等现代方法进行试验研究。
基金Research in the R.P.laboratory is currently supported by the ENW and TTW domains of the Netherlands Organisation for Scientific Research(NWO)Research in the C.L.B.laboratory is supported by ANPCyT,UBACyTCONICET.C.L.B.also acknowledges support from The New Phytologist Trust.
文摘Plants detect and respond to the proximity of competitors using light signals perceived by photoreceptor proteins.A low ratio of red to far-red radiation(R:FR ratio)is a key signal of competition that is sensed by the photoreceptor phytochrome B(phyB).Low R:FR ratios increase the synthesis of growth-related hormones,including auxin and gibberellins,promoting stem elongation and other shade-avoidance responses.Other photoreceptors that help plants to optimize their developmental configuration and resource allocation patterns in the canopy include blue light photoreceptors,such as cryptochromes and phototropins,and UV receptors,such as UVR8.All photoreceptors act by directly or indirectly controlling the activity of two major regulatory nodes for growth and development:the COP1/SPA ubiquitin E3 ligase complex and the PIF transcription factors.phyB is also an important modulator of hormonal pathways that regulate plant defense against herbivores and pathogens,including the jasmonic acid signaling pathway,In this Perspective,we discuss recent advances on the studies of the mechanisms that link photoreceptors with growth and defense.Understanding these mechanisms is important to provide a functional platform for breeding programs aimed at improving plant productivity,stress tolerance,and crop health in species of agronomic interest,and to manipulate the light environments in protected agriculture.
文摘In Arabidopsis seeds, germination is promoted only by phytochromes, principally phytochrome B （phyB） and phytochrome A （phyA）. Despite the abundant information concerning the molecular basis of phyB signaling downstream of PIF1/PIL5, the signaling network inducing germination by phyA is poorly known. Here, we describe the influence of phyA on the transcriptome of Arabidopsis seeds when germination is induced by a far-red （FR） pulse. The expression of 11% of the genome was significantly regulated by phyA. Most of the genes were up-regulated and the changes noted late （i.e. 5 h after a FR pulse）, whereas changes in down-regulated genes were more abundant earlier （i.e. 0.5 h after a FR pulse）. Auxin- and GA-associated elements were overrepresented in the genes that were modified by phyA. A significant number of genes whose expression was affected by phyA had not been previously reported to be dependent on PIL5. Among them, homozygotic mutant seeds of MYB66, a SAUR-like protein, PIN7, and GASA4 showed an impaired promo- tion of germination by phyA. Natural variation at the transcriptional level was found in early signaling and GA metabolic genes, but not in ABA metabolic and expansin genes between Columbia and Landsberg erecta accessions. Although phyA and phyB/PIL5 signaling pathways share some molecular components, our data suggest that phyA signaling is partially independent of PIL5 when germination is promoted by very low fluences of light.
文摘We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana. Afternoon shade events promoted hypocotyl growth, while morning shade was ineffective. The Ihy-D, elf3, lux, pif4 pifS, tocl, and quadruple della mutants retained the response to afternoon shade and the lack of response to morning shade while the Ihyccal mutant responded to both morning and afternoon shade. ThephyB mutant, plants overexpressing the multidrug resistance-like membrane protein ABCB19, and the iaa17/axr3 loss-of-function mutant failed to respond to shade. Transient exposure of sunlight-grown seedlings to synthetic auxin in the afternoon caused a stronger promotion of hypocotyl growth than morning treatments. The promotion of hypocotyl growth by afternoon shade or afternoon auxin required light perceived by phytochrome A or cryptochromes during the previous hours of the photoperiod. Although the ELF4-ELF3-LUX complex, PIF4, PIF5, and DELLA are key players in the generation of diurnal hypocotyl-growth patterns, they exert a minor role in the control of the diurnal pattern of growth responses to shade. We conclude that the strong diurnal dependency of hypocotyl-growth responses to shade relates to the balance between the antagonistic actions of LHY-CCA1 and a light-derived signal.
文摘Reactive oxygen species are in all types of organisms from microbes to higher plants and animals.They are by-products of normal metabolism,such as photosynthesis and respiration,and are responsive to abiotic and biotic stress.Accumulating evidence suggests reactive oxygen species play a vital role in programmed cell death,stress responses,plant defense against pathogens and systemic stress signaling in conjunction with antioxidant production.Here,we propose that reactive oxygen species and antioxidants,as both universal and evolutionarily conserved,are likely to play important role(s)in symbiotic interactions.To support this hypothesis we review the root and foliar fungal endophyte literature specific to fungal-plant symbiotum production of reactive oxygen species and antioxidants in response to stress.These asymptomatic fungi can produce antioxidants in response to both biotic and abiotic stress when grown in culture as well as in planta.In addition,there is a growing but nascent literature reporting a significant impact of endophyte colonization on the antioxidant activity of colonized(E+)hosts when compared to uncolonized(E-)hosts,especially when exposed to stress.Here we summarize general patterns emerging from the growing literature specific to antioxidant activity of endophytes in colonized hosts and bring up possible future research questions and approaches.The consequences of changes in reactive oxygen species production and increased antioxidant activity in the symbiotum appear to be beneficial in many instances;but costs are also indicated.Unexplored questions are:1)to what extent do antioxidants originating from the fungal endophyte mediate host metabolism,and thereby control host responses to endophyte colonization;(2)what role do fungal,plant,or symbiotum produced reactive oxygen species and antioxidants have in determining symbiotic outcome between extremes of pathogenicity and mutualism;and(3)what role if any,do the production of reactive oxygen species and their antioxidant counterparts play in th
基金supported by the UBACyT 20020170100265BAthe Agencia Nacional de Promociòn Científica y Tecnològica of Argentina(PICT2016-1784 and PICT2017-0583)to J.F.B.
文摘Seed dormancy is a developmental checkpoint that prevents mature seeds from germinating under conditions that are otherwise favorable for germination.Temperature and light are themost relevant environmental factors that regulate seed dormancy and germination.These environmental cues can trigger molecular and physiological responses including hormone signaling,particularly that of abscisic acid and gibberellin.The balance between the content and sensitivity of these hormones is the key to the regulation of seed dormancy.Temperature and light tightly regulate the transcription of thousands of genes,as well as other aspects of gene expression such asmRNAsplicing,translation,and stability.Chromatin remodeling determines specific transcriptional outputs,and alternative splicing leads to different outcomes and produces transcripts that encode proteins with altered or lost functions.Proper regulation of chromatin remodeling and alternative splicing may be highly relevant to seed germination.Moreover,microRNAs are also critical for the control of gene expression in seeds.This review aims to discuss recent updates on post-transcriptional regulation during seed maturation,dormancy,germination,and post-germination events.We propose future prospects for understanding howdifferent post-transcriptional processes in crop seeds can contribute to the design of genotypes with better performance and higher productivity.
基金This work was supported by the UBA[UBACyT20020170100695BA,UBACyT20020130100501BA]and ANPCyT[PICT 2015-0396].
文摘Early detection of infected asymptomatic plants could prevent the dissemination of tomatobacterial canker throughout the crop and, thus, reduce associated economic losses. Reflectance spectroscopy has been proposed for the detection of diseases in plants, mainlycaused by foliar fungal pathogens. In contrast, bacterial canker is a vascular disease thatdoes not produce visible foliar symptoms until it is too late to avoid contagion to otherplants. The effects of the disease on the conductivity of the xylem have an impact onthe water content of the leaves;initially, a subtle effect that cannot be assessed with thenaked eye but can be evaluated by reflectance spectroscopy. The objective of this workwas to identify indices, based on the reflectance spectral signature of the plants, for thedetection of tomato plants affected by bacterial canker prior to the appearance of symptoms. To verify that the proposed methodology is applicable to a broad range of tomatogenotypes, two experiments were carried out with different tomato cultivars grown in potsand another on the ground in a greenhouse. Plants were inoculated with the pathogenicbacteria and the reflectance spectrum of the apical leaflet of two leaves per plant wereobtained before symptoms expression;several spectral indices were calculated from thereflectance spectra. Three indices, of the shortwave-infrared zone, allowed the detectionof bacterial canker inoculated plants in a fast and non-destructive way, up to one weekbefore symptoms were visible: Normalized Difference Water Index (NDWI), Simple Ratioof Water Index (SRWI) and Water Index 1 180 (WI1180). Our research demonstrates, forthe first time, the usefulness of spectral indices sensitive to water content for the identifi-cation of diseased plants. These indices arise as a promising tool for the early detection ofvascular plant diseases, that could be integrated into sustainable management plans.
基金supported by CAPES—Coordination for the Improvement of Higher Education Personnel within the Ministry of Education of Brazil,and financial support from the Brazilian National Research Council and from ANII-Uruguay projects FSA-PP-2018-148651,FSA-PI-2018-148819 and FSA-PP-2018-1-148336.
文摘The Rio de la Plata region comprises central Argentina,Uruguay,and southern Brazil.Modern agriculture developed around 1900 with recent decades being characterized by the advance of cropping areas over native grasslands.Highly specialized agriculture has decoupled crop and livestock production but has succeeded in intensifying yields.However,significant losses of ecosystem services have been reported.Thus,questions have been raised on the sustainability of this pathway.A glance at world regions that have experienced similar trends suggests that an urgent course correction is needed.A major concern has been the lack of diversity in regions with highly specialized agriculture,promoting renewed interest in integrated crop-livestock systems(ICLS),not only because ICLS are more diverse than specialized systems,but also because they are rare examples of reconciliation between agroecosystem intensification and environmental quality.Consequently,this paper discusses alternatives to redesign multifunctional landscapes based on ICLS.Recent data provide evidence that recoupling crop and animal production increases the resilience of nutrient cycling functions and economic indicators to external stressors,enabling these systems to face climate-market uncertainty and reconcile food production with the provision of diverse ecosystem services.Finally,these concepts are exemplified in case studies where this perspective has been successfully applied.
基金Funding was provided by grants from FONCyT(PICT 00462)Universidad de Buenos Aires Ciencia y Técnica(UBACyT G0032)to MR Aguiar.
文摘Aims In arid communities,it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbour-ing bare ground areas.This becomes relevant in systems where the vegetation is distributed in patches surrounded by bare soil.However,whether roots of different species may be overlapping under bare ground areas is still controversial.The factors control-ling root responses when no plants appear to be directly influ-encing the gap among patches are still unclear.The aim of our study was to detect perennial grasses responses to an N enrich-ment pulse.Methods In a semi-arid steppe(Patagonia,Argentina),we buried root traps filled with sieved soil with and without N addition,under bare soil patches.Traps were harvested after 4 and 6 months.Trap neighbour-hoods(30 cm in diameter)included at least three of the dominant tussock species.After harvests,we identified species in the traps by root traits and quantified diversity,biomass and specific relative growth rates.Important Findings Bare ground areas show simultaneous root growth of different spe-cies.Diversity of perennial grass roots was higher with N addition than without it in the first harvest(4 months),but this difference disappeared in the second harvest(6 months).Root biomass was maximal after 6 months in N addition traps.Species preferred by herbivores(Bromus pictus and Poa ligularis)showed rapid growth and responses to N addition.Differences between harvests may be an indicative that N pulses interact with rising temperatures and soil water content as growing season progress.
文摘Fungal endophytes are suggested to manipulate host grass reproduction.Using different grass-endophyte combinations in a four year common garden experiment,we show that endophyte can retain control over the reproductive functions of the host.Plants were collected as seeds from two different environments,meadows and riverbanks.Natural endophyte infection(E+)increased reproductive effort of plants;13 and 15%higher proportion of E+plants produced panicles compared to naturally uninfected(E-)and manipulatively endophyte-infected(ME+)plants,respectively.Meadoworigin E+plants produced also higher number of panicles compared to E-in the last two years,and both meadow-and riverbank-origin ME+plants produced higher number of panicles compared to ME-plants in most of the years.Pseudovivipary was recorded in 5%of the plants each year.Pollen limitation appears not to induce pseudovivipary.Both E+and ME+plants produced higher number of seminiferous panicles compared to E-and ME-plants.The higher proportion of pseudoviviparism in ME+plants compared to E+,Eand ME-plants from meadows suggests specific genotypegenotype cross-talk between endophyte and grass.Pseudovivipary was affected by year and primarily explained by plant reproductive effort since most vigorous plants produced more pseudoviviparous panicles.We propose that endophytes can promote host grass reproduction in a habitatspecific manner and depending on genetic compatibility between partners.However,reproductive behavior depended on maternal habitat and the annual environmental conditions highlighting the importance of long-term experiments to estimate the effects of endophytes on host plant ecology.
文摘Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions.Epichloae fungal endophytes associate with cool-season grasses,growing systemically within the plant inter-cellular spaces and are transmitted through seeds.We explore the endophytes influence on the relationship between the plant reproductive and vegetative aboveground biomass(reproductive effort:RE)and on the trade-off between two components of the reproductive biomass,number and weight of panicles(RPN),using tall fescue as a model system.Naturally endophyte-colonized,manipulatively endophyte-free,and naturally endophyte-free plants from Northern European wild-populations together with the cultivar Kentucky-31 were grown under different environmental conditions(nutrients x water).The endophyte had an effect on the RPN(E+:6.19,ME-:4.68 and E-:4.40)which indicates how reproductive biomass is partitioned into number and mass of panicles,but not on RE(≈0.06).As expected,wild plants showed higher reproductive effort(≈0.06)compared to the cultivar KY-31(0.05),irrespective of endophyte presence.Endophyte-colonized plants had lighter panicles than endophyte-free plants,a pattern that was clear among low-yielding plants.Similarly,the tradeoff between RPN and RE was higher for endophytecolonized plants.This was again evident among plants with low RE indicating that colonized plants split the yield into either greater number of panicles and/or lighter panicles.The effect of vertically transmitted endophytes has earlier been studied as ratios(e.g.RE);however,our study shows that this approach may hide size-dependent endophyte effects on these relationships.Our study reveals that Neotyphodium endophyte affects trade-offs in tall fescue plants in a complex manner,and is influenced by a number of biological and abiotic factors.
基金supported by Finnish Academy grants 213401 and 209210Turku University Foundation.
文摘Pooideae grasses may be colonized by systemic fungal endophytes.The fitness of endophyte depends entirely on resources and seed transmission from the host plant,while colonized plants may gain increased survival,growth,and reproduction relative to their uncolonized conspecifics.Most research of endophyte-grass interactions have been carried out on few cultivars of tall fescue(Schedonorus phoenix)and their symbiont Neotyphodium coenophialum.Lack of studies using wild populations of tall fescue across the species natural distribution range,however,limits the understanding of the ecological and evolutionary role of the symbiosis in nature.We performed a common garden experiment in Southern Finland with three wild,tall fescue populations from northern Europe and the forage cultivar Kentucky-31(KY-31).For each population,we used naturally endophyte-colonized,naturally endophytecolonized but endophyte removed(decolonized),and naturally uncolonized plants to separate effects due to the host genotype from the endophyte.We evaluated growth variables and survival in four environmental treatments of varying water and nutrients.Supply of water and nutrients increased plant biomass and reproductive effort in all populations.This effect was higher for KY-31 plants which produced on average 55%more seeds than wild plants,indicating better adaptation to high resource environments.However,the higher incidence of Claviceps sp.and the low winter survival indicated KY-31 tall fescue is mal-adapted to Northern European conditions.Naturally colonized plants had greater plant biomass(≈12%),reproductive effort(≈22%)and seed mass(≈29%)than naturally uncolonized and decolonized plants.Nonetheless,endophyte colonization did not affect plant survival,and the effects of endophyte colonization on tiller number,panicle/tiller ratio and Claviceps sp.incidence depended on the population origin.In the wild populations,endophyte removal only reduced the number of tillers(≈29%lower),while the difference between naturally colonized and natur
基金funding from INTERACT(grant agreement No.262693)under the European Community’s Seventh Framework Programme,from Academy of Finland(Project No.137909)Spanish Government(Project AGL2011-22783).
文摘Epichloëfestucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra.This fungus is transmitted vertically from the mother plant to seeds.Hypothetically,the presence of E.festucae could affect the infection of a plant by other fungal species.This could occur if E.festucae metabolites produced in planta interfere negatively with other fungal infections;or alternatively,if the modulation of plant defenses by the endophyte favour further fungal infections.We have analyzed the presence of culturable non-systemic endophytes in plants of F.rubra infected(E+)and not infected(E−)by E.festucae in two subarctic habitats,meadows and riverbanks in Northern Finland.The observed non-systemic endophyte infection frequencies were similar among E+and E−plants from riverbanks,and E+plants from meadows.In contrast to these,the infection frequency was significantly lower in E−plants from meadows.This result suggests that the presence of E.festucae is not a main factor determining the presence of non-systemic endophytes in plants.Instead,plant genetic characteristics related to compatibility with E.festucae and other endophytes in the more stable meadow populations might play a role in these fungus–fungus–plant interactions.As a result of the survey,18 different taxa of non-systemic endophytes were identified in plants of F.rubra.All were ascomycetes except for one basidiomycete.Three endophytic taxa could not be ascribed to a genus,but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.
