microRNA参与植物次生代谢与非生物胁迫的调控

微RNA(microRNA,miRNA)为广泛存在于真核生物中的约16 ～ 29个核苷酸长度的内源非编码单链RNA分子,在植物中参与细胞增殖、分化、代谢、器官形成以及抵御盐、温度、干旱、重金属胁迫等方面的调节.植物miRNA主要通过对靶基因降解或抑制靶基因的表达,影响植物的生长发育.目前对miRNA的产生与调控方式的研...     

Characterization of microRNAs Expressed during Secondary Wall Biosynthesis in Acacia mangium

MicroRNAs (miRNAs) play critical regulatory roles by acting as sequence specific guide during secondary wall formation in woody and non-woody species. Although thousands of plant miRNAs have been sequenced, there is no comprehensive view of miRNA mediated gene regulatory network to provide profound biological insights into the regulation of xylem development. Herein, we report the involvement of six highly conserved amg-miRNA families (amg-miR166, amg-miR172, amg-miR168, amg-miR159, amg-miR394, and amg-miR156) as the potential regulatory sequences of secondary cell wall biosynthesis. Within this highly conserved amg-miRNA family, only amg-miR166 exhibited strong differences in expression between phloem and xylem tissue. The functional characterization of amg-miR166 targets in various tissues revealed three groups of HD-ZIP III: ATHB8, ATHB15, and REVOLUTA which play pivotal roles in xylem development. Although these three groups vary in their functions, -psRNA target analysis indicated that miRNA target sequences of the nine different members of HD-ZIP III are always conserved. We found that precursor structures of amg-miR166 undergo exhaustive sequence variation even within members of the same family. Gene expression analysis showed three key lignin pathway genes: C4H, CAD, and CCoAOMT were upregulated in compression wood where a cascade of miRNAs was downregulated. This study offers a comprehensive analysis on the involvement of highly conserved miRNAs implicated in the secondary wall formation of woody plants.     

蒙古沙冬青保守microRNAs的鉴定及靶基因预测

蒙古沙冬青(Ammopiptanthus mongolicus)是生长在荒漠中的木本植物, 对于我国西北部干旱、半干旱区域的植被维护与恢复具有重要价值。蒙古沙冬青对干旱、低温等多种逆境具有较高的耐受性, 是研究林木耐受逆境生理与分子机制的合适材料。MicroRNA(miRNA)是一类长度约为21个核苷酸的内源性非编码小分子RNA, 在植物生长发育和逆境应答等生物学过程中发挥着重要的调控作用。目前, 许多植物物种的miRNAs已经获得鉴定, 但未见蒙古沙冬青miRNAs的相关报道。文章应用高通量测序和生物信息学分析方法对蒙古沙冬青幼苗保守miRNAs的类型、表达丰度以及靶基因进行了分析和预测。共鉴定了10个家族的19种保守miRNAs, 其表达丰度介于55~1920269个拷贝之间。通过在线软件psRNATarget预测了其中14个保守miRNAs的靶基因。对于这些靶基因的功能分析表明, 蒙古沙冬青的保守miRNA主要通过转录调控、激素信号途径、物质代谢和胁迫应答等生物学过程参与植物生长发育和环境响应。     

A Genomic and Molecular View of Wood Formation

Wood formation is a process derived from plant secondary growth. Different from primary growth, plant secondary growth is derived from cambium meristem cells in the vascular and cork cambia and leads to the girth increase of the plant trunk. In the secondary growth process, plants convert most of photosynthesized products into various biopolymers for use in the formation of woody tissues. This article summarizes the new developments of genomic and genetic characterization of wood formation in herbaceous model plant and tree plant systems. Genomic studies have categorized a collection of the genes for which expression is associated with secondary growth. During wood formation, the expression of many genes is regulated in a stage-specific manner. The function of many genes involved in wood biosyntheses and xylem differentiation has been characterized. Although great progress has been achieved in the molecular and genomic understanding of plant secondary growth in recent years, the profound genetic mechanisms underlying this plant development remain to be investigated. Completion of the first tree genome sequence (Populus genome) provides a valuable genomic resource for characterization of plant secondary growth.     

Genome-wide Expression Profiling in Seedlings of the Arabidopsis Mutant uro that is Defective in the Secondary Cell Wall Formation

Plant secondary growth is of tremendous importance, not only for plant growth and development but also for economic usefulness. Secondary tissues such as xylem and phloem are the conducting tissues in plant vascular systems, essentially for water and nutrient transport, respectively. On the other hand, products of plant secondary growth are important raw materials and renewable sources of energy. Although advances have been recently made towards describing molecular mechanisms that regulate secondary growth, the genetic control for this process is not yet fully understood. Secondary cell wall formation in plants shares some common mechanisms with other plant secondary growth processes. Thus, studies on the secondary cell wall formation using Arabidopsis may help to understand the regulatory mechanisms for plant secondary growth. We previously reported phenotypic characterizations of an Arabidopsis semi-dominant mutant, upright rosette （uro）, which is defective in secondary cell wall growth and has an unusually soft stem. Here, we show that lignification in the secondary cell wall in uro is aberrant by analyzing hypocotyl and stem. We also show genome-wide expression profiles of uro seedlings, using the Affymetrix GeneChip that contains approximately 24 000 Arabidopsis genes. Genes identified with altered expression levels include those that function in plant hormone biosynthesis and signaling, cell division and plant secondary tissue growth. These results provide useful information for further characterizations of the regulatory network in plant secondary cell wall formation.     

Diversity and evolution of MicroRNA gene clusters

microRNA (miRNA) gene clusters are a group of miRNA genes clustered within a proximal distance on a chromosome. Although a large number of miRNA clusters have been uncovered in animal and plant genomes, the functional consequences of this arrangement are still poorly understood. Located in a polycistron, the coexpressed miRNA clusters are pivotal in coordinately regulating multiple processes, including embryonic development, cell cycles and cell differentiation. In this review, based on recent progress, we discuss the genomic diversity of miRNA gene clusters, the coordination of expression and function of the clustered miRNAs, and the evolutionarily adaptive processes with gain and loss of the clustering miRNA genes mediated by duplication and transposition events. Supported by State Key Program of National Natural Science of China(Grant No. 306300130)     

Evolution of class III homeodomain-leucine zipper genes in streptophytes

Land plants underwent tremendous evolutionary change following the divergence of the ancestral lineage from algal relatives. Several important developmental innovations appeared as the embryophyte clade diversified, leading to the appearance of new organs and tissue types. To understand how these changes came about, we need to identify the fundamental genetic developmental programs that are responsible for growth, patterning, and differentiation and describe how these programs were modified and elaborated through time to produce novel morphologies. Class III homeodomain-leucine zipper (class III HD-Zip) genes, identified in the model plant Arabidopsis thaliana, provide good candidates for basic land plant patterning genes. We show that these genes may have evolved in a common ancestor of land plants and their algal sister group and that the gene family has diversified as land plant lineages have diversified. Phylogenetic analysis, expression data from nonflowering lineages, and evidence from Arabidopsis and other flowering plants indicate that class III HD-Zip genes acquired new functions in sporophyte apical growth, vascular patterning and differentiation, and leaf development. Modification of expression patterns that accompanied diversification of class III HD-Zip genes likely played an important role in the evolution of land plant form.