The aim of this study was to evaluate the growth of rape （Brassica napus L.） seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown und...The aim of this study was to evaluate the growth of rape （Brassica napus L.） seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown under different light intensities of red and blue light provided by light-emitting diodes （LEDs） and their self-adjustment ability and changes in leaf microstructure were evaluated. Light was supplied by red LEDs with peak wavelengths of 630 （R1） and 660 nm （R2） and by blue LEDs （B） with a peak wavelength of 445 nm （the light intensity ratio of R1：R2：B was 3：3：2）, at intensities of 400 （R1R2B400）, 300 （R1R2B300）, and 200 μmol m-2 s-1 （R1R2B200）. Natural solar light served as the control （C）. Plant height, stem diameter, root length, leaf area, and dry weight of rape seedlings gradually increased with increasing light intensity. The seedlings in the R1R2B400 treatment grew more vigorously, while those in the R1R2B200 treatment were weaker. The photosynthetic pigment contents did not differ significantly between the R1R2B400 treatment and C, but were significantly lower in the R1R2B300 and R1R2B200 treatments. The highest intercellular CO2concentration, stomatal conductance, and transpiration rate were in the R1R2B300 treatment. The highest photosynthetic rate was in the R1R2B400 treatment, and was related to more compact leaves, thicker and tidier palisade and spongy tissues, and well-developed chloroplasts. In contrast, the seedlings in the R1R2B200 treatment had disordered mesophyll cells, round chloroplasts, and fractured and fuzzy grana lamellae, all of which inhibited plant growth. In conclusion, the seedlings in the R1R2B400 treatment had well-developed leaves, which favored photosynthesis. Compared with the light intensities below 300 μmol m-2 s-1, the light intensity of 400 μmol m-2 s-1 provided by a cembination of red and blue LEDs was beneficial for cultivating strong and healthy rape seedlings in an artificial system.展开更多
Increasing leaf photosynthesis per area（A） is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight（SL...Increasing leaf photosynthesis per area（A） is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight（SLW）. Twelve rice cultivars, including 6 indica and 6 japonica varieties, were pot-grown under two N treatments, low N（LN） and sufficient N（SN）. Leaf photosynthesis and related parameters were measured at tillering stage. Compared with LN treatment, A, stomatal conductance（g_s）, mesophyll conductance（g_m）, leaf N content（N_（area））, and chlorophyll content were significantly improved under SN treatment, while SLW and photosynthetic N use efficiency（PNUE） were generally decreased. Varietal difference in A was positively related to both g_s and g_m, but not related to N_（area）. This resulted in a low PNUE in high N_（area） leaves. Varietal difference in PNUE was generally negatively related to SLW. Response of PNUE to N supply varied among different rice cultivars, and interestingly, the decrease in PNUE under SN was negatively related to the decrease in SLW. With a higher N_（area）, japonica rice cultivars did not show a higher A than indica rice cultivars because of possession of high-SLW leaves. Therefore, varietal difference in A was not related to N_（area）, and SLW can substantially interfere with the correlation between A and N_（area）. These findings may provide useful information for rice breeders to maximize A and PNUE, rather than over reliance on N_（area） as an indicator of photosynthetic performance.展开更多
All nuclei in mesophyll cells of Artemisia marschalliana are located in vacuoles and occupy up to 90% of their volume. The ultrastructural organization of chromatin in nuclei shows different degrees of its decondensat...All nuclei in mesophyll cells of Artemisia marschalliana are located in vacuoles and occupy up to 90% of their volume. The ultrastructural organization of chromatin in nuclei shows different degrees of its decondensation, up to complete separation of DNA from histones. It is possible that the separation of DNA from histones enables Artemisia to grow in soils with high salinity.展开更多
In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming....In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming.In the present study on the effect of the hydrothermal regime at the flare sites on mesophyll and stomatal functional traits of Betula pubescens,leaves were collected from trees at250 m(control site[CS]),200,150 and 100 m(maximum impact site[MIS])from a flare.From the CS to MIS site,the average annual air temperature increased by 0.5℃and bog water level decreased by 17 cm.On plants from the MIS,stomata were 16%smaller and density was 20%lower compared to those at the CS,resulting in lower maximum stomatal conductance in plants from the MIS(mean±SE:MIS 0.84±0.05 mol·m^(-2)s^(-1),CS 1.24±0.06 mol·m^(-2)s^(-1);F=12.6,P<0.01).Mesophyll cell volume was 1.9 times lower at MIS than at CS.Chloroplast numbers per cell also declined with distance from the flares,from 21(MIS)to18(CS;F=15.6,P<0.001),and chloroplast volume was 24%higher at the CS,whereas the number of mesophyll cells and chloroplasts numbers per unit leaf area were 1.9 and 1.8 times higher at the MIS than at the CS,respectively.As a result,leaves from the MIS had a large total mesophyll cell(Ames/A)and chloroplast(Achl/A)surface area per unit leaf area,resulting in a 46%increase in mesophyll conductance in plants from the MIS.Thus,structural changes in leaf epidermis consisted of a decrease in stomatal size and number,could lower transpiration losses with higher temperatures and less water.To compensate for the reduction in leaf conductance due to a decrease in stomatal conductance under these conditions,an increase in the number of mesophyll cells and chloroplasts per unit area provides a greater gas-exchange area and mesophyll conductance.展开更多
Atmospheric CO_(2)concentration is elevated globally,which has“CO_(2)fertilization effects”and potentially improves plant photosynthesis,yield,and productivity.Despite the beneficial effect of CO_(2)fertilization be...Atmospheric CO_(2)concentration is elevated globally,which has“CO_(2)fertilization effects”and potentially improves plant photosynthesis,yield,and productivity.Despite the beneficial effect of CO_(2)fertilization being modulated by vapor pressure deficit(VPD),the underlying mechanism is highly uncertain.In the present study,the potential roles of hormones in determining CO_(2)fertilization effects under contrasting high and low VPD conditions were investigated by integrated physiological and transcriptomic analyses.Beneficial CO_(2)fertilization effects were offset under high VPD conditions and were constrained by plant water stress and photosynthetic CO_(2)utilization.High VPD induced a large passive water driving force,which disrupted the water balance and consequently caused plant water deficit.Leaf water potential,turgor pressure,and hydraulic conductance declined under high VPD stress.The physiological evidence combined with transcriptomic analyses demonstrated that abscisic acid(ABA)and jasmonic acid(JA)potentially acted as drought-signaling molecules in response to high VPD stress.Increased foliar ABA and JA content triggered stomatal closure to prevent excessive water loss under high VPD stress,which simultaneously increased the diffusion resistance for CO_(2)uptake from atmosphere to leaf intercellular space.High VPD also significantly increased mesophyll resistance for CO_(2)transport from stomatal cavity to fixation site inside chloroplast.The chloroplast“sink”CO_(2)availability was constrained by stomatal and mesophyll resistance under high VPD stress,despite the atmospheric“source”CO_(2)concentration being elevated.Thus,ABA-and JA-mediated drought-resistant mechanisms potentially modified the beneficial effect of CO_(2)fertilization on photosynthesis,plant growth,and yield productivity.This study provides valuable information for improving the utilization efficiency of CO_(2)fertilization and a better understanding of the physiological processes.展开更多
Protoplast fusion has great potential in citrus improvement. Although citrus mesophyll protoplasts usually cannot divide and regenerate,symmetric protoplast fusion of embryogenic callus protoplast + mesophyll protopla...Protoplast fusion has great potential in citrus improvement. Although citrus mesophyll protoplasts usually cannot divide and regenerate,symmetric protoplast fusion of embryogenic callus protoplast + mesophyll protoplast sometimes results in the regeneration of mesophyllparent-type cybrids. It suggested that mitochondrial DNA(mt DNA) from protoplasts of embryogenic callus parent plays an important role in stimulating division and regeneration of mesophyll protoplasts. Herein, somatic fusion was conducted via electrofusion between callus protoplasts isolated from Valencia orange [Citrus sinensis(L.) Osbeck] cell suspension cultures and transgenic GFP-tagged mesophyll protoplasts from the same genotype, i.e. transgenic Valencia orange plants containing the green fluorescent protein(GFP) gene, in an effort to elucidate whether mt DNA of callus line could stimulate the division and regeneration of mesophyll protoplasts from the same genotype. Two embryoids and one plantlet with GFP expression were successfully obtained and subsequent ploidy analysis by flow cytometry indicated that they were all diploids. The regenerated diploid embryoids and plantlet with GFP expression could be considered as ‘cybrids' with mt DNA from the callus protoplasts of Valencia orange. The result indicated that citrus mesophyll-parent-type cybrid regeneration needed the stimulation of mt DNA from protoplasts of embryogenic callus parent regardless of their origin either from another genotype or the same genotype as the mesophyll parent.展开更多
The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmenta...The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.展开更多
The microscopic and ultrastructural characteristics of mesophyll cells in flag leaves of two rice lines （a thermosensitive line 4628 and a thermo-resistant line 996） under high temperature stress （37℃ during 8：00...The microscopic and ultrastructural characteristics of mesophyll cells in flag leaves of two rice lines （a thermosensitive line 4628 and a thermo-resistant line 996） under high temperature stress （37℃ during 8：00-17：00 and 30℃ during 17：00-8：00） were investigated using an optical and a transmission electron microscopy. The membrane permeability and malondialdehyde content increased under the high temperature stress, and the increase of both variables was greater in the line 4628 than in the line 996. Under the high temperature stress, the line 996 showed tightly arranged mesophyll cells in flag leaves, fully developed vascular bundles and some closed stomata, whereas the line 4628 suffered from injury because of undeveloped vascular bundles, loosely arranged mesophyll cells and opened stomata. The mesophyll cells in flag leaves of the line 4628 were severely damaged under the high temperature stress, i.e. the chloroplast envelope became blurred, the grana thylakoid layer was arranged loosely and irregularly, the stroma layer disappeared, many osmiophilic granules appeared within the chloroplast, the outer membrane of mitochondria and the nucleus disintegrated and became blurred, the nucleolus disappeared, and much fibrillar-granular materials appeared within the nucleus. In contrast, the mesophyll cells in flag leaves of the line 996 maintained an intact ultrastructure under the high temperature stress. From these results, it is suggested that the ultrastructural modification of the cell membrane system is the primary plant response to high temperature stress and can be used as an index to evaluate the crop heat tolerance.展开更多
Monoallelic gene expression refers to the phenomenon that all transcripts of a gene in a cell are expressed from only one of the two alleles in a diploid organism. Although monoallelic gene expression has been occasio...Monoallelic gene expression refers to the phenomenon that all transcripts of a gene in a cell are expressed from only one of the two alleles in a diploid organism. Although monoallelic gene expression has been occasionally reported with bulk transcriptome analysis in plants, how prevalent it is in individual plant cells remains unknown. Here, we developed a single-cell RNA-seq protocol in rice and investigated allelic expression patterns in mesophyll cells of indica （93-11 ） and japonica （Nipponbare） inbred lines, as well as their F1 reciprocal hybrids. We observed pervasive monoallelic gene expression in individual mesophyll cells, which could be largely explained by stochastic and independent transcription of two alleles. By con- trast, two mechanisms that were proposed previously based on bulk transcriptome analyses, parent-of- origin effects and allelic repression, were not well supported by our data. Furthermore, monoallelically expressed genes exhibited a number of characteristics, such as lower expression levels, narrower H3K4me3/H3K9acJH3K27me3 peaks, and larger expression divergences between 93-11 and Nipponbare. Taken together, the development of a single-cell RNA-seq protocol in this study offers us an excellent opportunity to investigate the origins and prevalence of monoallelic gene expression in plant cells.展开更多
In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses ofElaeagnus angustifolia L. to different environmental factors, epide...In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses ofElaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy （SEM）, and mesophyll structure was studied by light microscopy （LM） and transmission electron microscopy （TEM）. Materials were selected from Linze County, Gansu Province （material A） and Qitai County, Xinjiang Uygur Autonomous Region （material B） of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in ma- terial A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stel- late-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford re- sistance to environmental stress.展开更多
Cadmium(Cd)is a deleterious non-essential metal in plants.To elucidate the mechanisms by which zinc(Zn)application alleviates cadmium(Cd)toxicity in wheat,we characterized plant growth,antioxidant system,leaf cell ult...Cadmium(Cd)is a deleterious non-essential metal in plants.To elucidate the mechanisms by which zinc(Zn)application alleviates cadmium(Cd)toxicity in wheat,we characterized plant growth,antioxidant system,leaf cell ultrastructure,and Cd transporter gene expression in winter wheat under Cd exposure(50μmol L^(-1)Cd)with foliar Zn application in a hydroponic experiment.Results showed that Zn addition(Zn+Cd)or pretreatment(pre-Zn+Cd)at 2 g L^(-1)as Zn_(S)O_(4)·7H_(2)O significantly exacerbated Cd-induced growth inhibition and diminished root morphological parameters,root cell viability,and chlorophyll content.In addition,the Cd content increased in roots and shoots in the Zn+Cd and pre-Zn+Cd treatments,but the Cd translocation factor decreased,when compared to the treatment without Zn application.After Zn application,the Cd content increased in the root cell wall fraction but decreased in the soluble fraction.The activities of antioxidative enzymes(superoxide dismutase,peroxidase,and catalase)and the contents of non-enzymatic antioxidants(malondialdehyde,ascorbic acid,and glutathione)significantly increased in the roots and shoots of wheat after Cd exposure,particularly in the Zn+Cd and pre-Zn+Cd treatments.Gene expression analysis showed that five genes(TaHMA2,TRIAE5370,TCONS1113,TRIAE5770,TRIAE1060,and TCONS5200)participated in root absorption of Cd,whereas TCONS5200 and TRIAE5660 contributed to Cd transfer to shoots.Foliar application of Zn increased the number of chloroplasts,but the chloroplast structure was destroyed in the Zn+Cd treatment.These results indicated that 2 g L^(-1)ZnSO4·7H2O increased the toxicity of 50μmol L^(-1)Cd.Increased Cd uptake due to the upregulated expression of Cd transporter genes and increased reactive oxygen species accumulation may be the reasons why Zn application aggravated Cd toxicity.展开更多
基金funded by the National High-Tech R&D Program of China (2013AA103003)the Agricultural Research Special Funds for Public Welfare Projects,China (201303108)
文摘The aim of this study was to evaluate the growth of rape （Brassica napus L.） seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown under different light intensities of red and blue light provided by light-emitting diodes （LEDs） and their self-adjustment ability and changes in leaf microstructure were evaluated. Light was supplied by red LEDs with peak wavelengths of 630 （R1） and 660 nm （R2） and by blue LEDs （B） with a peak wavelength of 445 nm （the light intensity ratio of R1：R2：B was 3：3：2）, at intensities of 400 （R1R2B400）, 300 （R1R2B300）, and 200 μmol m-2 s-1 （R1R2B200）. Natural solar light served as the control （C）. Plant height, stem diameter, root length, leaf area, and dry weight of rape seedlings gradually increased with increasing light intensity. The seedlings in the R1R2B400 treatment grew more vigorously, while those in the R1R2B200 treatment were weaker. The photosynthetic pigment contents did not differ significantly between the R1R2B400 treatment and C, but were significantly lower in the R1R2B300 and R1R2B200 treatments. The highest intercellular CO2concentration, stomatal conductance, and transpiration rate were in the R1R2B300 treatment. The highest photosynthetic rate was in the R1R2B400 treatment, and was related to more compact leaves, thicker and tidier palisade and spongy tissues, and well-developed chloroplasts. In contrast, the seedlings in the R1R2B200 treatment had disordered mesophyll cells, round chloroplasts, and fractured and fuzzy grana lamellae, all of which inhibited plant growth. In conclusion, the seedlings in the R1R2B400 treatment had well-developed leaves, which favored photosynthesis. Compared with the light intensities below 300 μmol m-2 s-1, the light intensity of 400 μmol m-2 s-1 provided by a cembination of red and blue LEDs was beneficial for cultivating strong and healthy rape seedlings in an artificial system.
基金supported by the National Natural Science Foundation of China(31301840)the National Excellent Doctoral Dissertation of China(201465)+2 种基金the Program for Changjiang Scholars and Innovative Research Team in University of China(IRT1247)the Natural Science Foundation of Hubei Province,China(2013CFB201)the Fundamental Research Funds for the Central Universities,China(2013PY107)
文摘Increasing leaf photosynthesis per area（A） is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight（SLW）. Twelve rice cultivars, including 6 indica and 6 japonica varieties, were pot-grown under two N treatments, low N（LN） and sufficient N（SN）. Leaf photosynthesis and related parameters were measured at tillering stage. Compared with LN treatment, A, stomatal conductance（g_s）, mesophyll conductance（g_m）, leaf N content（N_（area））, and chlorophyll content were significantly improved under SN treatment, while SLW and photosynthetic N use efficiency（PNUE） were generally decreased. Varietal difference in A was positively related to both g_s and g_m, but not related to N_（area）. This resulted in a low PNUE in high N_（area） leaves. Varietal difference in PNUE was generally negatively related to SLW. Response of PNUE to N supply varied among different rice cultivars, and interestingly, the decrease in PNUE under SN was negatively related to the decrease in SLW. With a higher N_（area）, japonica rice cultivars did not show a higher A than indica rice cultivars because of possession of high-SLW leaves. Therefore, varietal difference in A was not related to N_（area）, and SLW can substantially interfere with the correlation between A and N_（area）. These findings may provide useful information for rice breeders to maximize A and PNUE, rather than over reliance on N_（area） as an indicator of photosynthetic performance.
文摘All nuclei in mesophyll cells of Artemisia marschalliana are located in vacuoles and occupy up to 90% of their volume. The ultrastructural organization of chromatin in nuclei shows different degrees of its decondensation, up to complete separation of DNA from histones. It is possible that the separation of DNA from histones enables Artemisia to grow in soils with high salinity.
基金performed within the budget themes of the Institute Botanic Garden UB RASthe framework of the state assignment FEWZ-2020–0009 from the Ministry of Education and Science of the Russian Federation。
文摘In petroleum-producing territories of West Siberia(Russia),oil well gas flares have a thermal effect on nearby plant communities.Such communities can be used as models for studying plant acclimation to global warming.In the present study on the effect of the hydrothermal regime at the flare sites on mesophyll and stomatal functional traits of Betula pubescens,leaves were collected from trees at250 m(control site[CS]),200,150 and 100 m(maximum impact site[MIS])from a flare.From the CS to MIS site,the average annual air temperature increased by 0.5℃and bog water level decreased by 17 cm.On plants from the MIS,stomata were 16%smaller and density was 20%lower compared to those at the CS,resulting in lower maximum stomatal conductance in plants from the MIS(mean±SE:MIS 0.84±0.05 mol·m^(-2)s^(-1),CS 1.24±0.06 mol·m^(-2)s^(-1);F=12.6,P<0.01).Mesophyll cell volume was 1.9 times lower at MIS than at CS.Chloroplast numbers per cell also declined with distance from the flares,from 21(MIS)to18(CS;F=15.6,P<0.001),and chloroplast volume was 24%higher at the CS,whereas the number of mesophyll cells and chloroplasts numbers per unit leaf area were 1.9 and 1.8 times higher at the MIS than at the CS,respectively.As a result,leaves from the MIS had a large total mesophyll cell(Ames/A)and chloroplast(Achl/A)surface area per unit leaf area,resulting in a 46%increase in mesophyll conductance in plants from the MIS.Thus,structural changes in leaf epidermis consisted of a decrease in stomatal size and number,could lower transpiration losses with higher temperatures and less water.To compensate for the reduction in leaf conductance due to a decrease in stomatal conductance under these conditions,an increase in the number of mesophyll cells and chloroplasts per unit area provides a greater gas-exchange area and mesophyll conductance.
基金y the National Natural Science Foundation of China(Grant No.32102466)the Major Scientific Innovation Project of Shandong Province(Grant No.2022CXGC020708).
文摘Atmospheric CO_(2)concentration is elevated globally,which has“CO_(2)fertilization effects”and potentially improves plant photosynthesis,yield,and productivity.Despite the beneficial effect of CO_(2)fertilization being modulated by vapor pressure deficit(VPD),the underlying mechanism is highly uncertain.In the present study,the potential roles of hormones in determining CO_(2)fertilization effects under contrasting high and low VPD conditions were investigated by integrated physiological and transcriptomic analyses.Beneficial CO_(2)fertilization effects were offset under high VPD conditions and were constrained by plant water stress and photosynthetic CO_(2)utilization.High VPD induced a large passive water driving force,which disrupted the water balance and consequently caused plant water deficit.Leaf water potential,turgor pressure,and hydraulic conductance declined under high VPD stress.The physiological evidence combined with transcriptomic analyses demonstrated that abscisic acid(ABA)and jasmonic acid(JA)potentially acted as drought-signaling molecules in response to high VPD stress.Increased foliar ABA and JA content triggered stomatal closure to prevent excessive water loss under high VPD stress,which simultaneously increased the diffusion resistance for CO_(2)uptake from atmosphere to leaf intercellular space.High VPD also significantly increased mesophyll resistance for CO_(2)transport from stomatal cavity to fixation site inside chloroplast.The chloroplast“sink”CO_(2)availability was constrained by stomatal and mesophyll resistance under high VPD stress,despite the atmospheric“source”CO_(2)concentration being elevated.Thus,ABA-and JA-mediated drought-resistant mechanisms potentially modified the beneficial effect of CO_(2)fertilization on photosynthesis,plant growth,and yield productivity.This study provides valuable information for improving the utilization efficiency of CO_(2)fertilization and a better understanding of the physiological processes.
基金financially supported by the National Natural Science Foundation of China (Nos. 31530065, 31521092)the Ministry of Education of China (IRT_17R45)
文摘Protoplast fusion has great potential in citrus improvement. Although citrus mesophyll protoplasts usually cannot divide and regenerate,symmetric protoplast fusion of embryogenic callus protoplast + mesophyll protoplast sometimes results in the regeneration of mesophyllparent-type cybrids. It suggested that mitochondrial DNA(mt DNA) from protoplasts of embryogenic callus parent plays an important role in stimulating division and regeneration of mesophyll protoplasts. Herein, somatic fusion was conducted via electrofusion between callus protoplasts isolated from Valencia orange [Citrus sinensis(L.) Osbeck] cell suspension cultures and transgenic GFP-tagged mesophyll protoplasts from the same genotype, i.e. transgenic Valencia orange plants containing the green fluorescent protein(GFP) gene, in an effort to elucidate whether mt DNA of callus line could stimulate the division and regeneration of mesophyll protoplasts from the same genotype. Two embryoids and one plantlet with GFP expression were successfully obtained and subsequent ploidy analysis by flow cytometry indicated that they were all diploids. The regenerated diploid embryoids and plantlet with GFP expression could be considered as ‘cybrids' with mt DNA from the callus protoplasts of Valencia orange. The result indicated that citrus mesophyll-parent-type cybrid regeneration needed the stimulation of mt DNA from protoplasts of embryogenic callus parent regardless of their origin either from another genotype or the same genotype as the mesophyll parent.
文摘The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.
基金supported by the National Natural Science Foundation of China (Grant No. 30500315)the Agricultural Technological Results Transformation Item of Ministry of Agriculture, China (Grant No. 05EFN214300193)the Educational Foundation of Hunan Province, China (Grant No. 07C360)
文摘The microscopic and ultrastructural characteristics of mesophyll cells in flag leaves of two rice lines （a thermosensitive line 4628 and a thermo-resistant line 996） under high temperature stress （37℃ during 8：00-17：00 and 30℃ during 17：00-8：00） were investigated using an optical and a transmission electron microscopy. The membrane permeability and malondialdehyde content increased under the high temperature stress, and the increase of both variables was greater in the line 4628 than in the line 996. Under the high temperature stress, the line 996 showed tightly arranged mesophyll cells in flag leaves, fully developed vascular bundles and some closed stomata, whereas the line 4628 suffered from injury because of undeveloped vascular bundles, loosely arranged mesophyll cells and opened stomata. The mesophyll cells in flag leaves of the line 4628 were severely damaged under the high temperature stress, i.e. the chloroplast envelope became blurred, the grana thylakoid layer was arranged loosely and irregularly, the stroma layer disappeared, many osmiophilic granules appeared within the chloroplast, the outer membrane of mitochondria and the nucleus disintegrated and became blurred, the nucleolus disappeared, and much fibrillar-granular materials appeared within the nucleus. In contrast, the mesophyll cells in flag leaves of the line 996 maintained an intact ultrastructure under the high temperature stress. From these results, it is suggested that the ultrastructural modification of the cell membrane system is the primary plant response to high temperature stress and can be used as an index to evaluate the crop heat tolerance.
基金supported by the National Basic Research Program of China (2014CB943500)the National Program for Support of Top-Notch Young Professionals+1 种基金the Recruitment Program of Global Youth Expertsthe State Key Laboratory of Plant Genomics (SKLPG2011B0103 and SKLPG2016C0219-01)
文摘Monoallelic gene expression refers to the phenomenon that all transcripts of a gene in a cell are expressed from only one of the two alleles in a diploid organism. Although monoallelic gene expression has been occasionally reported with bulk transcriptome analysis in plants, how prevalent it is in individual plant cells remains unknown. Here, we developed a single-cell RNA-seq protocol in rice and investigated allelic expression patterns in mesophyll cells of indica （93-11 ） and japonica （Nipponbare） inbred lines, as well as their F1 reciprocal hybrids. We observed pervasive monoallelic gene expression in individual mesophyll cells, which could be largely explained by stochastic and independent transcription of two alleles. By con- trast, two mechanisms that were proposed previously based on bulk transcriptome analyses, parent-of- origin effects and allelic repression, were not well supported by our data. Furthermore, monoallelically expressed genes exhibited a number of characteristics, such as lower expression levels, narrower H3K4me3/H3K9acJH3K27me3 peaks, and larger expression divergences between 93-11 and Nipponbare. Taken together, the development of a single-cell RNA-seq protocol in this study offers us an excellent opportunity to investigate the origins and prevalence of monoallelic gene expression in plant cells.
基金supported by the National Natural Science Foundation of China(Grant No.91125029)the State Key Development Program for Basic Research of China(973 Program,Grant No.2013CB429904)
文摘In order to obtain qualitative and quantitative characteristics of leaf epidermal micromorphology and mesophyll structure to evaluate the responses ofElaeagnus angustifolia L. to different environmental factors, epidermal micromorphology was observed by scanning electron microscopy （SEM）, and mesophyll structure was studied by light microscopy （LM） and transmission electron microscopy （TEM）. Materials were selected from Linze County, Gansu Province （material A） and Qitai County, Xinjiang Uygur Autonomous Region （material B） of China. Results show that lamina thickness was higher in material A, with one layer of epidermal cells in both adaxial and abaxial surfaces, and epidermal cell radial length was significantly longer in the adaxial surface. E. angustifolia leaves are typically bifacial, with a higher ratio of palisade to spongy tissue in material A. The thickness of trichome layer of epidermis was thicker in material A. In contrast, cell wall and cuticular wax of the epidermal cells were thinner in material A than in material B. Chloroplast ultrastructure was different with the approximate spherical chloroplast containing numerous starch grains and osmiophilic granules in ma- terial A, while only the spindly chloroplast contained starch grains in material B. Multiple layers of peltate or stel- late-peltate trichomes occupied both leaf surfaces in material A and the abaxial surface in material B, while the adaxial surface of material B contained few trichomes. Stomata were not observed on the leaf surfaces in materials A and B by SEM because of trichome obstruction. Our results indicate that the leaf structure of E. angustifolia is closely correlated with environmental factors, and the combination of leaf epidermal micromorphology and mesophyll structure afford re- sistance to environmental stress.
基金supported by the Postgraduate Education Reform and Quality Improvement Project of Henan Province of China(No.HNYJS2020KC17)the National Key R&D Program of China(No.2017YFD0201700)the National Natural Science Foundation of China(No.32002128).
文摘Cadmium(Cd)is a deleterious non-essential metal in plants.To elucidate the mechanisms by which zinc(Zn)application alleviates cadmium(Cd)toxicity in wheat,we characterized plant growth,antioxidant system,leaf cell ultrastructure,and Cd transporter gene expression in winter wheat under Cd exposure(50μmol L^(-1)Cd)with foliar Zn application in a hydroponic experiment.Results showed that Zn addition(Zn+Cd)or pretreatment(pre-Zn+Cd)at 2 g L^(-1)as Zn_(S)O_(4)·7H_(2)O significantly exacerbated Cd-induced growth inhibition and diminished root morphological parameters,root cell viability,and chlorophyll content.In addition,the Cd content increased in roots and shoots in the Zn+Cd and pre-Zn+Cd treatments,but the Cd translocation factor decreased,when compared to the treatment without Zn application.After Zn application,the Cd content increased in the root cell wall fraction but decreased in the soluble fraction.The activities of antioxidative enzymes(superoxide dismutase,peroxidase,and catalase)and the contents of non-enzymatic antioxidants(malondialdehyde,ascorbic acid,and glutathione)significantly increased in the roots and shoots of wheat after Cd exposure,particularly in the Zn+Cd and pre-Zn+Cd treatments.Gene expression analysis showed that five genes(TaHMA2,TRIAE5370,TCONS1113,TRIAE5770,TRIAE1060,and TCONS5200)participated in root absorption of Cd,whereas TCONS5200 and TRIAE5660 contributed to Cd transfer to shoots.Foliar application of Zn increased the number of chloroplasts,but the chloroplast structure was destroyed in the Zn+Cd treatment.These results indicated that 2 g L^(-1)ZnSO4·7H2O increased the toxicity of 50μmol L^(-1)Cd.Increased Cd uptake due to the upregulated expression of Cd transporter genes and increased reactive oxygen species accumulation may be the reasons why Zn application aggravated Cd toxicity.
