Root development is tightly controlled by light, and the response is thought to depend on signal transmission from the shoot. Here, we show that the root apical meristem perceives light independently from aboveground organs to activate the light-regulated transcription factor ELONGATED HYPOCOTYL5 (HY5). The ROS balance between H2O2 and superoxide anion in the root is disturbed under darkness with increased H2O2. We demonstrate that root-derived HY5 directly activates PER6 expression to eliminate H2O2. Moreover, HY5 directly represses UPBEAT1, a known inhibitor of peroxidases, to release the expression of PERs, partially contributing to the light control of ROS balance in the root. Our results reveal an unexpected ability in roots with specific photoreception and provide a mechanistic framework for the HY5-mediated interaction between light and ROS signaling in early root development.

[Objective]This study aims to determine the variations of leaf phenotypic traits and geographical differentiation patterns of Lithocarpus litseifolius（Hance）Chun,thus providing the practical guidance for its resource utilization.[Method]Taking 469 herbarium-specimen in 62 populations in the whole area as research objects,variance analysis,principal component analysis（PCA）and cluster analysis were used to study the variations of leaf phenotypic traits,geographical differentiation patterns and their correlation with major geographic-climate factors.The leaf phenotypic traits include leaf length（LL）,leaf width（LW）,leaf length-towidth ratio（LL/LW）,leaf tip length（TL）,leaf tip angle（TA）,petiole length（PL）,primary lateral veins（PLV）,leaf base angle（BA）and leaf area（LA）.[Result]（1）The variations of leaf phenotypic traits were significant;the variation coefficient ranged from 9.79%（TA）to 42.57%（TL）,and averaged at 22.59%.Leaf phenotypic traits showed significant variations across different populations（P＜0.01）.The variations of LL,LW,LL/LW,TL,TA,BA and LA were mainly exhibited across the population,while the variations of PL and PLV were exhibited both across and within the population.（2）There were significant or extremely significant correlations among leaf phenotypic traits;LL,LW and LA showed highly significant negative correlations with longitude;BA showed a highly significant negative correlation with latitude;LL and LA showed significant negative correlations with annual precipitation;BA showed a highly significant correlation with extreme minimum temperature. The variations of leaf phenotypic traits showed a pattern of double variation in latitude and longitude,while annual precipitation and extreme minimum temperature were the main driving factor.（3） From principal component analysis（PCA）,it was learned that 9 characteristics could be represented by 3 principal components（The cumulative contribution rate was 81.45%）,and 62 populations could be classified into 4 categories according to the cluster class of principle components.On a large landscape scale,populations did not cluster strictly based on geographical distance;On a smaller regional scale,populations that were closer in geographical distance clustered into a large group.[Conclusion]There were significant variations in the leaf phenotypic of L.litseifolius and had given priority to both longitude and latitude.The leaves of 62 populations could be divided into four categories:long lanceolate,wide lanceolate,long elliptic and wide elliptic.

自然界存在着成千上万种病毒,但动物并不是唯一的受害者.病毒会严重影响作物的产量和品质,不仅对植物自身造成不可逆转的伤害,同时也会对寄主依赖的生态系统造成毁灭性打击.目前,植物病毒病已经成为全球第二大植物病害,对农作物、蔬菜和园艺植物造成重大破坏,导致大面积减产甚至绝收.在全球范围内,植物病毒病害每年造成的经济损失达600亿美元,已经成为全球农业所面临的严峻挑战之一[1].

Stem cell populations in all multicellular organisms are situated in a niche, which is a special microenvironment that defines stem cell fate. The interplay between stem cells and their niches is crucial for stem cell maintenance. Here, we show that an endogenous stress-related signal (ESS) is overrepresented in the shoot stem cell niche under natural growth conditions, and the vast majority of known stem-cell-specific and niche-specific genes responded to stress signals. Interference with the ESS in the stem cell niche by blocking ethylene signalling impaired stem cell maintenance. Ethylene-insensitive 3 (EIN3), the key transcription factor in ethylene signalling, directly actives the expression of the stress hub transcription factor AGAMOUS-LIKE 22 ( AGL22 ) in the stem cell niche and relays ESS signals to the WUSCHEL/CLAVATA network. Our results provide a mechanistic framework for ESS signalling control of the stem cell niche and demonstrate that plant stem cells are maintained by a native stress microenvironment in vivo.

以木姜叶柯浙江庆元、江西赣州、广东惠州3个种源内的25个家系材料为对象,研究了家系间4个种实生物学性状的变异.结果表明:同一种源不同家系间单果重、果长、每果穗果实数、果穗长生物学性状中至少有3个以上表现极显著差异,其中单果重和果长在所有家系中均达到极显著差异,说明在种源内以特定性状开展优良家系选择很有意义;种实生物学性状之间存在一定的相关性,江西赣州和广东惠州种源内家系的单果重与每果穗果实数之间达到极显著水平,江西赣州、广东惠州和浙江庆元种源内家系的果穗长与每果穗果实数之间达到极显著水平,广东惠州果长与每果穗种实数间呈负向显著水平.种源内家系均可分成多个小组,它们代表了家系内单果重、果长、每果穗果实数及果穗长之间的关系,单果较轻时,伴随着果实长、每果穗果实多、果穗较长,而单果较重时,伴随着果实短、每果穗果实少、果穗较短.

Pecan (Carya illinoinensis) is a widely consumed edible woody oil species that is rich in unsaturated fatty acids (FAs) that are beneficial to human health. However, the genes and mechanisms regulating seed oil biosynthesis in pecan are not well understood. Here, we analyzed the expression patterns of genes involved in seed oil biosynthesis in two different varieties of pecan with distinct fruit maturation schedules and oil contents. We cloned the C. illinoinensis WRINKLED 1 (CiWRI1) gene, a homolog of ArabidopsisWRINKLED1 (AtWRI1), which plays a key role in FA synthesis. Overexpressing CiWRI1 restored lipid synthesis in the Arabidopsiswri1-1 mutant and rescued other phenotypic defects such as plant height, root length, and germination rate, suggesting that CiWRI1 is an ortholog of the AtWRI1 and is involved in the regulation of FA synthesis. To investigate the mechanism of CiWRI1 regulation, we cloned C. illinoinensis BIOTIN CARBOXYL CARRIER PROTEIN ISOFORM2 (CiBCCP2) and determined that the CiWRI1 protein directly binds to an ASML1/WRI1 (AW)-box motif in the CiBCCP2 gene promoter and thereby activates its transcription. CiBCCP2 overexpression partly rescued the phenotypic defects of the wri1-1 mutant, indicating that it is directly regulated by CiWRI1. Thus, de novo FA biosynthesis in seed is conserved across plant species; moreover, CiWRI1 regulates oil synthesis by directly controlling CiBCCP2 expression. These findings present novel potential targets for molecular-marker-assisted breeding of this commercially important plant.

[目的]研究薄壳山核桃(Carya illinoinensis)CiDGAT1基因的结构特征和表达模式,为深入分析CiDGAT1基因功能提供理论参考.[方法]以薄壳山核桃'波尼'果实为材料,利用DGAT1基因保守片段设计特异引物,通过3′RACE和RT-PCR技术,克隆薄壳山核桃的CiDGAT1基因.运用生物信息学方法分析其蛋白性质、亲缘进化关系及基因结构.通过实时荧光定量PCR分析该基因在不同品种以及果实不同发育时期的表达模式.[结果]克隆到1条薄壳山核桃油脂合成相关基因CiDGAT1,该基因开放阅读框(ORF)1617 bp,编码538个氨基酸,5′UTR区包含294个碱基,3′UTR区包含340个碱基.基因结构分析显示,CiDGAT1由15个外显子和14个内含子组成.系统进化分析表明CiDGAT1蛋白聚在双子叶植物分支中,与栎树(Quercus suber)QsDGAT1和榛子(Corylus americana)CaDGAT1的亲缘关系最近.实时荧光定量PCR结果表明,在早熟品种'波尼'和晚熟品种'马罕'与'金华'3个品种果实发育过程中,CiDGAT1在'波尼'发育时表达量较高,在145 d成熟期时达到最高,而'马罕'、'金华'品种在生长过程中,CiDGAT1表达量一直缓慢增长,152 d后迅速升高,至最后成熟时达到最高值.[结论]CiDGAT1属于MBOAT家族,在薄壳山核桃果实发育过程中表达量呈上升趋势,是油脂合成过程中重要的调控因子.

Stem cells in plants constantly supply daughter cells to form new organs and are expected to safeguard the integrity of the cells from biological invasion. Here, we show how stem cells of the Arabidopsis shoot apical meristem and their nascent daughter cells suppress infection by cucumber mosaic virus (CMV). The stem cell regulator WUSCHEL responds to CMV infection and represses virus accumulation in the meristem central and peripheral zones. WUSCHEL inhibits viral protein synthesis by repressing the expression of plant S-adenosyl-l-methionine-dependent methyltransferases, which are involved in ribosomal RNA processing and ribosome stability. Our results reveal a conserved strategy in plants to protect stem cells against viral intrusion and provide a molecular basis for WUSCHEL-mediated broad-spectrum innate antiviral immunity in plants.

The key steps of transcription are coupled with the opening of the DNA helical structure and establishment of active chromatin to facilitate the movement of the transcription machinery. Type I topoisomerases cleave one DNA strand and relax the supercoiled structure of transcribed templates. How topoisomerase-mediated DNA topological changes promote transcription and establish a permissive histone modification for transcription elongation is largely unknown. Here, we show that TOPOISOMERASE 1α in plants regulates FLOWERING LOCUS C transcription by coupling histone modification and transcription machinery. We demonstrate that TOP1α directly interacts with the methyltransferase SDG8 to establish high levels of H3K36 methylation downstream of FLC transcription start sites and recruits RNA polymerase II to facilitate transcription elongation. Our results provide a mechanistic framework for TOP1α control of the main steps of early transcription and demonstrate how topoisomerases couple RNA polymerase II and permissive histone modifications to initiate transcription elongation.

The classic phytohormone auxin plays an essential role in priming meristematic cell differentiation in the shoot apical meristem to promote lateral organ initiation. Recently, several lines of evidence have suggested that auxin is not only transported to new primordia but also descends to the stem cells in the central zone. However, the function of auxin in stem cell regulation has remained elusive. Here, we show that auxin signaling in stem cells is mediated, at least in part, by AUXIN RESPONSE FACTOR 5/MONOPTEROS (ARF5/MP), which directly represses the transcription of DORNROSCHEN/ENHANCER OF SHOOT REGENERATION 1 (DRN/ESR1). DRN expressed in stem cells positively regulates CLAVATA3 (CLV3) expression and has important meristematic functions. Our results provide a mechanistic framework for auxin control of shoot stem cell homeostasis and demonstrate how auxin differentially controls plant stem cell maintenance and differentiation.

The ERECTA family genes, ERECTA (ER), ERECTA-LIKE1 (ERL1), and ERECTA-LIKE2 (ERL2), encode leucine-rich repeat receptor-like kinases in Arabidopsis thaliana. Knocking out these three genes can cause severe phenotypes, which indicates that they play significant roles in plant growth and development. However, the molecular mechanism within remains unclear. Here we show that the short hypocotyl phenotypes of er erl1 erl2 mutants are mainly due to the defects of cell elongation rather than the cell division. In contrast, in the ERECTA overexpression transgenic plants, the hypocotyl length is increased with elongated cells. Moreover, we show that the er erl1 erl2 triple mutant contains a low level of auxin, and the expression levels of the key auxin biosynthesis genes are significantly reduced. Consistent with this observation, increasing exogenous or endogenous auxin levels could partially rescue the cell elongation defects of the er erl1 erl2 triple mutant. Therefore, our results provide a molecular basis for auxin mediated ERECTA control of the hypocotyl length in Arabidopsis thaliana.

Despite the importance of stem cells in plant and animal development, the common mechanisms of stem cell maintenance in both systems have remained elusive. Recently, the importance of hydrogen peroxide (H2O2) signaling in priming stem cell differentiation has been extensively studied in animals. Here, we show that different forms of reactive oxygen species (ROS) have antagonistic roles in plant stem cell regulation, which were established by distinct spatiotemporal patterns of ROS‐metabolizing enzymes. The superoxide anion ( ) is markedly enriched in stem cells to activate WUSCHEL and maintain stemness, whereas H2O2 is more abundant in the differentiating peripheral zone to promote stem cell differentiation. Moreover, H2O2 negatively regulates biosynthesis in stem cells, and increasing H2O2 levels or scavenging leads to the termination of stem cells. Our results provide a mechanistic framework for ROS‐mediated control of plant stem cell fate and demonstrate that the balance between and H2O2 is key to stem cell maintenance and differentiation. Superoxide regulates plant stem cell fate, and the balance between superoxide and H2O2 serves as a key switch for stem cell maintenance versus differentiation by antagonistically regulating expression of stem cell fate transcription factor WUSCHEL. Superoxide regulates plant stem cell fate, and the balance between superoxide and H2O2 serves as a key switch for stem cell maintenance versus differentiation by antagonistically regulating expression of stem cell fate transcription factor WUSCHEL.

As the development of research tools in molecular biology,plant developmental biology has been changed its focus from the descriptive analysis of plant morphology to the cellular and gene regulation level.Plants have distinct postembryonic development patterns compare to the animal,which give the plant a flexible developmental plasticity in response to different growth environments.In the long-term of evolution,plants are adapted to the environment changes through the continuous adjustment of their development strategy,which makes the plant world highly diverse.The growth and development of multicellular organisms depend on the maintenance and constant differentiation of stem cells.In plants,most of the organs originate from stem cells where resided in the shoot apical meristem,root apical meristem and cambium.The functional conservation of stem cells in those diverse plants is the basis for ontogenesis.However,from the perspective of evolutionary development,the diversity of key regulatory genes expression in different stem cell populations fulfills the continuous adjustments of development strategy to adapt to environmental changes.The plasticity in stem cell regulations determines the flexibility of plant development,which is conserved in plant kingdom from moss to angiosperms.Of course,the mechanism of stem cell maintenance and differentiation are even more complicated in angiosperms.In model plant of Arabidopsis thanian,the molecular mechanism of stem cell regulations has been extensively studied over the past decades.Multiple signaling molecules and transcription factors are found to tightly control the stem cell fate in Arabidopsis thaliana.The homeodomain transcription factor WUSCHEL (WUS) where expressed in the organizing center (OC) is a key regulator for plant stem cell fate determination.While,stem cells expressed secreted peptide CLV3,negatively regulates the expression of WUS.They form a negative feedback loop that tightly control plant stem cell fate.In addition,the classic phytohormones cytokinin and auxin also play essential roles in the maintenance of stem cells in shoot apical meristem,root apical meristem and cambium,and exhibit complex functional interactions.The molecular organization of the RAM is quite similar to that of the shoot.WOX5 (WUSCHEL-RELATED HOMEOBOX 5),a homologue of WUS,is expressed in the QC,and induces root stem cell fate in the surrounding cells.The GRAS family transcription factor SHORT-ROOT (SHR) is expressed in the innermost tissue of the root,and SHR moves to the surrounding cell layer activating SCARECROW (SCR),together with PLT1 and PLT2,defines the stem cells fate.In this review,we focused on the functions of plant stem cells in plant postembryonic development,and covered recent findings on plant hormonal regulation in stem cells.We also discussed the integration of endogenous genetic information and external environmental factors in plant development,and how they affected the development of organs,morphology and yield of crops.

•Mutation of WRKY13 causes weaker stem phenotype.•Mutation of WRKY13 causes reduced sclerenchyma development and altered lignin synthesis.•Several secondary cell wall synthesis genes were affected in wrky13 mutants and NST2 is the direct downstream gene of WRKY13.

Plant stem cells are hypersensitive to environmental hazards throughout their life cycle, but the mechanism by which plants safeguard stem cell homeostasis in response to environmental hazards is largely unknown. The homeodomain transcription factor WUSCHEL (WUS) protein maintains the stem cell pool in the shoot apical meristem of Arabidopsis. Here, we demonstrate that the translation of WUS mRNA is directed by an internal ribosomal entry site (IRES) located in the 5'-untranslated region. The AtLa1 protein, an RNA-binding factor, binds to the 5'-untranslated region and initiates the IRES-dependent translation of WUS mRNA. Knockdown of AtLa1 expression represses the WUS IRES-dependent translation and leads to the arrest of growth and development. The AtLa1 protein is mainly located in the nucleoplasm. However, environmental hazards promote the nuclear-to-cytoplasmic translocation of the AtLa1 protein, which further enhances the IRES-dependent translation of WUS mRNA. Genetic evidence indicates that the WUS protein increases the tolerance of the shoot apical meristem to environmental hazards. Based on these results, we conclude that the stem cell niche in Arabidopsis copes with environmental hazards by enhancing the IRES-dependent translation of WUS mRNA under the control of the AtLa1 protein.

Previous studies have demonstrated that petal shape and size in legume flowers are determined by two separate mechanisms, dorsoventral (DV) and organ internal (IN) asymmetric mechanisms, respectively. However, little is known about the molecular mechanisms controlling petal development in legumes. To address this question, we investigated petal development along the floral DV axis in Lotus japonicus with respect to cell and developmental biology by comparing wild-type legumes to mutants. Based on morphological markers, the entire course of petal development, from initiation to maturity, was grouped to define 3 phases or 13 stages. In terms of epidermal micromorphology from adaxial surface, mature petals were divided into several distinct domains, and characteristic epidermal cells of each petal differentiated at stage 9, while epidermal cells of all domains were observed until stage 12. TCP and MIXTA-like genes were found to be differentially expressed in various domains of petals at stages 9 and 12. Our results suggest that DV and IN mechanisms interplay at different stages of petal development, and their interaction at the cellular and molecular level guides the elaboration of domains within petals to achieve their ideal shape, and further suggest that TCP genes determine petal identity along the DV axis by regulating MIXTA-like gene expression.

To investigate the genetic loci to regulate the development of petal shape, screening of the mutation affecting lateral petal development was conducted in a model plant of legume, Lotus japonicus . Two independent mutants, kew2 and kew3 with the similar phenotype were obtained, whose shape of lateral petal is altered and resembles the one of ventral petal in the wild type. Genetic analysis showed that kew3 was caused by the same single recessive locus and allelic to the one of kew1 , a formal identified mutant in the locus KEW1 . KEW1 has been shown to be an ortholog of K in pea, but whose mutation at the molecular level is unsolved yet. Furthermore, genetic analyses of kew2 indicate that there are other genetic factors which could interact with kew and involve in the lateral petal development. Analysis of these mutations and cloning the corresponding loci will shield light on the underlying molecular mechanism in the control of floral asymmetry and facilitate our understanding on the evolution of the zygomorphic development.

The fragile X mental retardation protein (FMRP) is a RNA-binding protein proposed to post-transcriptionally regulate the expression of genes important for neuronal development and synaptic plasticity. We previously demonstrated that FMRP binds to its own FMR1 mRNA via a guanine-quartet (G-quartet) RNA motif. However, the functional effect of this binding on FMR1 expression was not established. In this work, we characterized the FMRP binding site (FBS) within the FMR1 mRNA by a site directed mutagenesis approach and we investigated its importance for FMR1 expression. We show that the FBS in the FMR1 mRNA adopts two alternative G-quartet structures to which FMRP can equally bind. While FMRP binding to mRNAs is generally proposed to induce translational regulation, we found that mutations in the FMR1 mRNA suppressing binding to FMRP do not affect its translation in cellular models. We show instead that the FBS is a potent exonic splicing enhancer in a mini-gene system. Furthermore, FMR1 alternative splicing is affected by the intracellular level of FMRP. These data suggest that the G-quartet motif present in the FMR1 mRNA can act as a control element of its alternative splicing in a negative autoregulatory loop.

Zygomorphic flowers, with bilateral (dorsoventral) symmetry, are considered to have evolved several times independently in flowering plants. In Antirrhinum majus, floral dorsoventral symmetry depends on the activity of two TCP-box genes, CYCLOIDEA (CYC) and DICHOTOMA (DICH). To examine whether the same molecular mechanism of floral asymmetry operates in the distantly related Rosid clade of eudicots, in which asymmetric flowers are thought to have evolved independently, we investigated the function of a CYC homologue LjCYC2 in a papilionoid legume, Lotus japonicus. We showed a role for LjCYC2 in establishing dorsal identity by altering its expression in transgenic plants and analyzing its mutant allele squared standard 1 (squ1). Furthermore, we identified a lateralizing factor, Keeled wings in Lotus 1 (Kew1), which plays a key role in the control of lateral petal identity, and found LjCYC2 interacted with Kew1, resulting in a double mutant that bore all petals with ventralized identity to some extents. Thus, we demonstrate that CYC homologues have been independently recruited as determinants of petal identities along the dorsoventral axis in two distant lineages of flowering plants, suggesting a common molecular origin for the mechanisms controlling floral zygomorphy.