The cuticle is the outer physical barrier of aerial plant surfaces and an important interaction point between plants and the environment. Many environmental stresses affect cuticle formation, yet the regulatory pathwa...The cuticle is the outer physical barrier of aerial plant surfaces and an important interaction point between plants and the environment. Many environmental stresses affect cuticle formation, yet the regulatory pathways involved remain undefined. We used a genetics and gene expression analysis in Arabidopsis thaliana to define an abscisic acid （ABA） signaling loop that positively regulates cuticle formation via the core ABA signaling pathway, including the PYR/PYL receptors, PP2C phosphatase, and SNF1-Related Protein Kinase （SnRK） 2.21SnRK2.3/SnRK2.6. Downstream of the SnRK2 kinases, cuticle formation was not regulated by the ABA-responsive element-binding transcription factors but rather by DEWAX, MYB16, MYB94, and MYB96. Additionally, low air humidity increased cuticle formation independent of the core ABA pathway and cell death/reactive oxygen species signaling attenuated expression of cuticle-biosynthesis genes. In Physcornitrella patens, exogenous ABA suppressed expression of cuticle- related genes, whose Arabidopsis orthologs were ABA-induced. Hence, the mechanisms regulating cuticle formation are conserved but sophisticated in land plants. Signaling specifically related to cuticle deficiency was identified to play a major role in the adaptation of ABA signaling pathway mutants to increased humidity and in modulating their immunity to Botrytis cinerea in Arabidopsis. These results define a cuticle-specific downstream branch in the ABA signaling pathway that regulates responses to the external environment.展开更多
Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environmen...Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.展开更多
Terrestrial floras underwent important changes during the Lopingian （Late Permian）, Early Triassic, and Middle Triassic, i.e., before, during, and after the end-Permian mass extinction. An accurate account of these ...Terrestrial floras underwent important changes during the Lopingian （Late Permian）, Early Triassic, and Middle Triassic, i.e., before, during, and after the end-Permian mass extinction. An accurate account of these developments requires reliable correlation. Macrofossils of land plants can only provide a low-resolution biostratigraphy, while detailed zonation schemes based on palynomorphs are available for many regions. Their applicability is still limited due to several factors, such as （micro-）floral provincialism, a lack of suitable marker taxa commonly occurring at important boundaries, and in many cases a lack of independent age control. Nevertheless, these palynostratigraphic schemes are regularly used for dating and correlation of successions between different regions. To support such efforts, the biozonation schemes based on palynomorphs from the Lopingian up to and including the Middle Triassic from across the world are summarized and revised. Thus, a consistent correlation of palynozones with the currently recognized international stages is established.展开更多
Land plants and algae form a supergroup, the Archaeplastida, believed to be monophyletic. We report the results of an analysis of the phylogeny of putative globins in the currently available genomes to bacterial and o...Land plants and algae form a supergroup, the Archaeplastida, believed to be monophyletic. We report the results of an analysis of the phylogeny of putative globins in the currently available genomes to bacterial and other eu- karyote hemoglobins （Hbs）. Archaeplastida genomes have 3/3 and 2/2 Hbs, with the land plant genomes having group 2 2/ 2 Hbs, except for the unexpected occurrence of two group 1 2/2 Hbs in Ricinus communis. Bayesian analysis shows that plant 3/3 Hbs are related to vertebrate neuroglobins and bacterial flavohemoglobins （FHbs）. We sought to define the bacterial groups, whose ancestors shared the precursors of Archaeplastida Hbs, via Bayesian and neighbor-joining anal- yses based on COBALTalignment of representative sets of bacterial 3/3 FHb-like globins and group I and 2 2/2 Hbs with the corresponding Archaeplastida Hbs. The results suggest that the Archaeplastida 3/3 and group 1 2/2 Hbs could have orig- inated from the horizontal gene transfers （HGTs） that accompanied the two generally accepted endosymbioses of a pro- teobacterium and a cyanobacterium with a eukaryote ancestor. In contrast, the origin of the group 2 212 Hbs unexpectedly appears to involve HGT from a bacterium ancestral to Chloroflexi, Deinococcales, Bacilli, and Actinomycetes. Furthermore, although intron positions and phases are mostly conserved among the land plant 3/3 and 2/2 globin genes, introns are absent in the algal 3/3 genes and intron positions and phases are highly variable in their 2/2 genes. Thus, introns are irrelevant to globin evolution in Archaeplastida.展开更多
The conservation of plants has not generated the sense of urgency—or the funding—that drives the conservation of animals,although plants are far more important for us. There are an estimated 500,000 species of land ...The conservation of plants has not generated the sense of urgency—or the funding—that drives the conservation of animals,although plants are far more important for us. There are an estimated 500,000 species of land plants( angiosperms,gymnosperms,ferns,lycophytes,and bryophytes),with diversity strongly concentrated in the humid tropics. Many species are still unknown to science. Perhaps a third of all land plants are at risk of extinction,including many that are undescribed,or are described but otherwise data deficient. There have been few known global extinctions so far,but many additional species have not been recorded recently and may be extinct. Although only a minority of plant species have a specific human use,many more play important roles in natural ecosystems and the services they provide,and rare species are more likely to have unusual traits that could be useful in the future. The major threats to plant diversity include habitat loss,fragmentation,and degradation,overexploitation,invasive species,pollution,and anthropogenic climate change. Conservation of plant diversity is a massive task if viewed globally,but the combination of a well-designed and well-managed protected area system and ex situ gap-filling and back-up should work anywhere. The most urgent needs are for the completion of the global botanical inventory and an assessment of the conservation status of the 94% of plant species not yet evaluated,so that both in and ex situ conservation can be targeted efficiently.Globally,the biggest conservation gap is in the hyperdiverse lowland tropics and this is where attention needs to be focused.展开更多
Data of Paleozoic and some Early Triassic vascular land plant fossils from South China are synthetically analyzed,revealing evolutionary characteristics of Paleozoic vascular land plant diversity.Vascular land plant d...Data of Paleozoic and some Early Triassic vascular land plant fossils from South China are synthetically analyzed,revealing evolutionary characteristics of Paleozoic vascular land plant diversity.Vascular land plant diversity keeps increasing in the Paleozoic as a whole.The Silurian witnessed the earliest evolution and initial diversification of land plants.From the Early Devonian to the Early Carboniferous(Mississippian),the great development,diversification,and differentiation really occurred in vascular land plants,with fluctuations of diversity,rapid replacement of the plant types,and an all-out takeover of terrestrial ecological niches.From the Early Permian,land plant diversity dramatically increased,and reached a climax in the Middle-Late Permian.Comparisons between late Paleozoic marine and terrestrial biodiversity reveal co-evolution of the late Paleozoic animals and plants as well as the individual evolutionary patterns of sea/land ecosystems.Vascular land plant diversity dramatically declined in the Frasnian as a result of the F/F event,and the end-Permian mass extinctions completely turned over the phytogroups.展开更多
The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctio...The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates（amphibians and reptiles）, though some workers advocate a sudden endTriassic（TJB） extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform（different changes in different places）, not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP（Central Atlantic Magmatic Province） eruptions, which caused significant environmental perturbations（cooling, warming, acidification） through outga展开更多
文摘The cuticle is the outer physical barrier of aerial plant surfaces and an important interaction point between plants and the environment. Many environmental stresses affect cuticle formation, yet the regulatory pathways involved remain undefined. We used a genetics and gene expression analysis in Arabidopsis thaliana to define an abscisic acid （ABA） signaling loop that positively regulates cuticle formation via the core ABA signaling pathway, including the PYR/PYL receptors, PP2C phosphatase, and SNF1-Related Protein Kinase （SnRK） 2.21SnRK2.3/SnRK2.6. Downstream of the SnRK2 kinases, cuticle formation was not regulated by the ABA-responsive element-binding transcription factors but rather by DEWAX, MYB16, MYB94, and MYB96. Additionally, low air humidity increased cuticle formation independent of the core ABA pathway and cell death/reactive oxygen species signaling attenuated expression of cuticle-biosynthesis genes. In Physcornitrella patens, exogenous ABA suppressed expression of cuticle- related genes, whose Arabidopsis orthologs were ABA-induced. Hence, the mechanisms regulating cuticle formation are conserved but sophisticated in land plants. Signaling specifically related to cuticle deficiency was identified to play a major role in the adaptation of ABA signaling pathway mutants to increased humidity and in modulating their immunity to Botrytis cinerea in Arabidopsis. These results define a cuticle-specific downstream branch in the ABA signaling pathway that regulates responses to the external environment.
文摘Charophytic algae and land plants together make up a monophyletic group, streptophytes, which represents one of the main lineages of multicellular eukaryotes and has contributed greatly to the change of the environment on earth in the Phanerozoic Eon. Significant progress has been made to understand phylogenetic relationships among members of this group by phylogenetic studies of morphological and molecular data over the last twenty-five years. Mesostigma viride is now regarded as among the earliest diverging unicellular organisms in streptophytes. Characeae are the sister group to land plants. Liverworts represent the first diverging lineage of land plants. Hornworts and lycophytes are extant representatives of bryophytes and vascular plants, respectively, when early land plants changed from gametophyte to sporophyte as the dominant generation in the life cycle. Equisetum, Psilotaceae, and ferns constitute the monophyletic group of monilophytes, which are sister to seed plants. Gnetales are related to conifers, not to angiosperms as previously thought. Amborella, Nymphaeales, Hydatellaceae, Illiciales, Trimeniaceae, and Austrobaileya represent the earliest diverging lineages of extant angiosperms. These phylogenetic results, together with recent progress on elucidating genetic and developmental aspects of the plant life cycle, multicellularity, and gravitropism, will facilitate evolutionary developmental studies of these key traits, which will help us to gain mechanistic understanding on how plants adapted to environmental challenges when they colonized the land during one of the major transitions in evolution of life.
基金supported by the Euregio Science Fund (call 2014, IPN16: "The end-Permian mass extinction in the Southern and Eastern Alps: extinction rates vs taphonomic biases in different depositional environments") of the Europaregion/Euregio Tirol-Südtirol-Trentino/Tirolo-Alto Adige-TrentinoSYNTHESYS (access call 4, 2016, GB-TAF-6751: "Diversity changes of spores and pollen during the Permian-Triassic mass extinction")
文摘Terrestrial floras underwent important changes during the Lopingian （Late Permian）, Early Triassic, and Middle Triassic, i.e., before, during, and after the end-Permian mass extinction. An accurate account of these developments requires reliable correlation. Macrofossils of land plants can only provide a low-resolution biostratigraphy, while detailed zonation schemes based on palynomorphs are available for many regions. Their applicability is still limited due to several factors, such as （micro-）floral provincialism, a lack of suitable marker taxa commonly occurring at important boundaries, and in many cases a lack of independent age control. Nevertheless, these palynostratigraphic schemes are regularly used for dating and correlation of successions between different regions. To support such efforts, the biozonation schemes based on palynomorphs from the Lopingian up to and including the Middle Triassic from across the world are summarized and revised. Thus, a consistent correlation of palynozones with the currently recognized international stages is established.
文摘Land plants and algae form a supergroup, the Archaeplastida, believed to be monophyletic. We report the results of an analysis of the phylogeny of putative globins in the currently available genomes to bacterial and other eu- karyote hemoglobins （Hbs）. Archaeplastida genomes have 3/3 and 2/2 Hbs, with the land plant genomes having group 2 2/ 2 Hbs, except for the unexpected occurrence of two group 1 2/2 Hbs in Ricinus communis. Bayesian analysis shows that plant 3/3 Hbs are related to vertebrate neuroglobins and bacterial flavohemoglobins （FHbs）. We sought to define the bacterial groups, whose ancestors shared the precursors of Archaeplastida Hbs, via Bayesian and neighbor-joining anal- yses based on COBALTalignment of representative sets of bacterial 3/3 FHb-like globins and group I and 2 2/2 Hbs with the corresponding Archaeplastida Hbs. The results suggest that the Archaeplastida 3/3 and group 1 2/2 Hbs could have orig- inated from the horizontal gene transfers （HGTs） that accompanied the two generally accepted endosymbioses of a pro- teobacterium and a cyanobacterium with a eukaryote ancestor. In contrast, the origin of the group 2 212 Hbs unexpectedly appears to involve HGT from a bacterium ancestral to Chloroflexi, Deinococcales, Bacilli, and Actinomycetes. Furthermore, although intron positions and phases are mostly conserved among the land plant 3/3 and 2/2 globin genes, introns are absent in the algal 3/3 genes and intron positions and phases are highly variable in their 2/2 genes. Thus, introns are irrelevant to globin evolution in Archaeplastida.
文摘The conservation of plants has not generated the sense of urgency—or the funding—that drives the conservation of animals,although plants are far more important for us. There are an estimated 500,000 species of land plants( angiosperms,gymnosperms,ferns,lycophytes,and bryophytes),with diversity strongly concentrated in the humid tropics. Many species are still unknown to science. Perhaps a third of all land plants are at risk of extinction,including many that are undescribed,or are described but otherwise data deficient. There have been few known global extinctions so far,but many additional species have not been recorded recently and may be extinct. Although only a minority of plant species have a specific human use,many more play important roles in natural ecosystems and the services they provide,and rare species are more likely to have unusual traits that could be useful in the future. The major threats to plant diversity include habitat loss,fragmentation,and degradation,overexploitation,invasive species,pollution,and anthropogenic climate change. Conservation of plant diversity is a massive task if viewed globally,but the combination of a well-designed and well-managed protected area system and ex situ gap-filling and back-up should work anywhere. The most urgent needs are for the completion of the global botanical inventory and an assessment of the conservation status of the 94% of plant species not yet evaluated,so that both in and ex situ conservation can be targeted efficiently.Globally,the biggest conservation gap is in the hyperdiverse lowland tropics and this is where attention needs to be focused.
基金supported by Chinese Academy of Sciences (Grant Nos. KZCX2-YW-105,KZCX2-YW-Q05-01)National Natural Science Foundation of China (Grant No. 40523004) National Basic Research Program of China (Grant No. 2006CB806400)
文摘Data of Paleozoic and some Early Triassic vascular land plant fossils from South China are synthetically analyzed,revealing evolutionary characteristics of Paleozoic vascular land plant diversity.Vascular land plant diversity keeps increasing in the Paleozoic as a whole.The Silurian witnessed the earliest evolution and initial diversification of land plants.From the Early Devonian to the Early Carboniferous(Mississippian),the great development,diversification,and differentiation really occurred in vascular land plants,with fluctuations of diversity,rapid replacement of the plant types,and an all-out takeover of terrestrial ecological niches.From the Early Permian,land plant diversity dramatically increased,and reached a climax in the Middle-Late Permian.Comparisons between late Paleozoic marine and terrestrial biodiversity reveal co-evolution of the late Paleozoic animals and plants as well as the individual evolutionary patterns of sea/land ecosystems.Vascular land plant diversity dramatically declined in the Frasnian as a result of the F/F event,and the end-Permian mass extinctions completely turned over the phytogroups.
文摘The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates（amphibians and reptiles）, though some workers advocate a sudden endTriassic（TJB） extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform（different changes in different places）, not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP（Central Atlantic Magmatic Province） eruptions, which caused significant environmental perturbations（cooling, warming, acidification） through outga
