查看更多>>摘要：The evolution of the latitudinal diversity gra-dient(LDG),characterized by a peak in diver-sity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cy-cads are among one of the oldest lineages of extant seed plants and have undergone ex-tensive diversification in the tropics.Intrigu-ingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly com-plete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integra-ted global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conserva-tism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced de-creased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the forma-tion of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cra-dles.Moreover,water-related climate variables,specifically precipitation seasonality and po-tential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms un-derpinning global biodiversity patterns.
Santosh Kumar RanaHum Kala RanaJacob B.LandisTianhui Kuang...
1192-1205页
查看更多>>摘要：The mountains of Southwest China comprise a sig-nificant large mountain range and biodiversity hot-spot imperiled by global climate change.The high species diversity in this mountain system has long been attributed to a complex set of factors,and re-cent large-scale macroevolutionary investigations have placed a broad timeline on plant diversification that stretches from 10 million years ago(Mya)to the present.Despite our increasing understanding of the temporal mode of speciation,finer-scale population-level investigations are lacking to better refine these temporal trends and illuminate the abiotic and biotic influences of cryptic speciation.This is largely due to the dearth of organismal sampling among closely related species and populations,spanning the in-credible size and topological heterogeneity of this region.Our study dives into these evolutionary dy-namics of speciation using genomic and eco-morphological data of Stellera chamaejasme L.We identified four previously unrecognized cryptic spe-cies having indistinct morphological traits and large metapopulation of evolving lineages,suggesting a more recent diversification(～2.67-0.90 Mya),largely influenced by Pleistocene glaciation and biotic fac-tors.These factors likely influenced allopatric spe-ciation and advocated cyclical warming-cooling episodes along elevational gradients during the Pleistocene.The study refines the evolutionary timeline to be much younger than previously im-plicated and raises the concern that projected future warming may influence the alpine species diversity,necessitating increased conservation efforts.
查看更多>>摘要：At the physiological level,the interplay between auxin and ethylene has long been recognized as crucial for the regulation of organ abscission in plants.How-ever,the underlying molecular mechanisms remain unknown.Here,we identified transcription factors involved in indoleacetic acid(IAA)and ethylene(ET)signaling that directly regulate the expression of IN-FLORESCENCE DEFICIENT IN ABSCISSION(IDA)and its receptor HAESA(HAE),which are key com-ponents initiating abscission.Specifically,litchi IDA-like 1(LcIDL1)interacts with the receptor HAESA-like 2(LcHSL2).Through in vitro and in vivo experiments,we determined that the auxin response factor LcARF5 directly binds and activates both LcIDL1 and LcHSL2.Furthermore,we found that the ETHYLENE INSENSITIVE 3-like transcription factor LcEIL3 di-rectly binds and activates LcIDL1.The expression of IDA and HSL2 homologs was enhanced in LcARF5 and LcEIL3 transgenic Arabidopsis plants,but re-duced in ein3 eil1 mutants.Consistently,the ex-pressions of LcIDL1 and LcHSL2 were significantly decreased in LcARF5-and LcEIL3-silenced fruitlet abscission zones(FAZ),which correlated with a lower rate of fruitlet abscission.Depletion of auxin led to an increase in 1-aminocyclopropane-1-carboxylic acid(the precursor of ethylene)levels in the litchi FAZ,followed by abscission activation.Throughout this process,LcARF5 and LcEIL3 were induced in the FAZ.Collectively,our findings suggest that the mo-lecular interactions between litchi AUXIN RESPONSE FACTOR 5(LcARF5)-LcIDL1/LcHSL2 and LcEIL3-LclDL1 signaling modules play a role in regulating fruitlet abscission in litchi and provide a long-sought mechanistic explanation for how the interplay be-tween auxin and ethylene is translated into the mo-lecular events that initiate abscission.
查看更多>>摘要：Carotenoids are important nutrients for human health that must be obtained from plants since they cannot be biosynthesized by the human body.Dissecting the regulatory mechanism of carotenoid metabolism in plants represents the first step toward manipu-lating carotenoid contents in plants by molecular design breeding.In this study,we determined that SIAP2c,an APETALA2(AP2)family member,acts as a transcriptional repressor to regulate carotenoid bi-osynthesis in tomato(Solanum lycopersicum).Knockout of SIAP2c in both the"MicroTom"and"Ailsa Craig"backgrounds resulted in greater lycopene accumulation,whereas overexpression of this gene led to orange-ripe fruit with significantly lower lycopene contents than the wild type.We es-tablished that SIAP2c represses the expression of genes involved in lycopene biosynthesis by directly binding to the cis-elements in their promoters.Moreover,SIAP2c relies on its EAR motif to recruit the co-repressors TOPLESS(TPL)2/4 and forms a complex with histone deacetylase(had)1/3,thereby reducing the histone acetylation levels of lycopene biosynthesis genes.Furthermore,SIAP2a,a homolog of SIAP2c,acts upstream of SIAP2c and alleviates the SIAP2c-induced repression of lycopene biosyn-thesis genes by inhibiting SIAP2c transcription during fruit ripening.Therefore,we identified a transcrip-tional cascade mediated by AP2 family members that regulates lycopene biosynthesis during fruit ripening in tomato,laying the foundation for the manipulation of carotenoid metabolism in plants.
查看更多>>摘要：L eaf senescence is an essential physiological process related to grain yield potential and nutritional quality.Green leaf duration(GLD)after anthesis directly reflects the leaf senescence process and exhibits large genotypic differences in common wheat;however,the underlying gene regulatory mechanism is still lacking.Here,we identified TaNAM-A1 as the causal gene of the major loci qGLD-6A for GLD during grain filling by map-based cloning.Transgenic assays and TILLING mutant analyses demonstrated that TaNAM-A1 played a critical role in regulating leaf senescence,and also affected spike length and grain size.Furthermore,the functional divergences among the three haplotypes of TaNAM-A1 were systematically evaluated.Wheat varieties with TaNAM-A1d(containing two mutations in the coding DNA sequence of TaNAM-A1)exhibited a longer GLD and superior yield-related traits com-pared to those with the wild type TaNAM-A1a.All three haplotypes were functional in activating the expression of genes involved in macromolecule degradation and mineral nutrient remobilization,with TaNAM-A1a showing the strongest activity and TaNAM-A1d the weakest.TaNAM-A1 also modulated the expression of the senescence-related transcription factors TaNAC-S-7A and TaNAC016-3A.TaNAC016-3A enhanced the tran-scriptional activation ability of TaNAM-A1a by protein-protein interaction,thereby promoting the senescence process.Our study offers new insights into the fine-tuning of the leaf functional period and grain yield formation for wheat breeding under various geographical climatic conditions.
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