Mechanisms of shoot apical function in gametophyte dominant and sporophyte dominant model plants

与动物不同，所有陆地植物的生活史都有一个单倍体配子体阶段。配子体是含有二倍体阶段一半染色体的多细胞植物，孢子体。在苔藓等苔藓植物中，配子体占主导地位，而在玉米等常见被子植物中，二倍体孢子体占主导地位。在所有情况下，地上结构的发育取决于顶端分生组织的活动，顶端分生组织是位于生长中的植物顶端的自繁殖干细胞池。分生组织结构的广泛变异在这些广泛的群体中进化；尽管存在这种结构变异，但在器官发生和干细胞更新期间的分生组织功能是保守的。地上部发育的主要进化创新包括孢子体世代对配子体的优势，以及产生光合作用叶片的多细胞地上部顶端分生组织的出现。在这个项目中，植物顶端基因表达网络的分析将确定古代配子体占优势的模式苔藓Marchantia dona和Physcomitrella patens与新近进化的孢子体占优势的被子植物玉米和拟南芥之间共同和独特的顶端分生组织发育机制。激光显微切割结合RNA测序将比较这些不同模式植物的顶端转录特征。将确定三类候选基因：(1)在玉米和拟南芥的配子体分生组织或侧器官和玉米和拟南芥的孢子体分生组织或侧器官之间功能共享的转录本；(2)四种模式生物中孢子体特有的转录本；(3)每个谱系和区域特有的转录本。在该项目期间产生的所有数据将发布到公共数据库，包括CosMoss数据库中的Physcomitrella patens转录组链接和能源部联合基因组研究所的多态Marchantia数据库。该项目还将为康奈尔大学植物生物学研究生提供基因组分析和植物发育机制方面的培训。

Unlike animals, all land plants have a haploid gametophyte stage of their life cycle. Gametophytes are multicellular plants that contain one half the chromosome complement of the diploid phase, the sporophyte. In bryophytes like mosses, the gametophyte is dominant, while in familiar angiosperms like maize the diploid sporophyte dominates. In all cases, development of above ground structures depends upon the activity of apical meristems, pools of self-propagating stem cells located at the growing plant tips. Widespread variation in meristem structure has evolved across these wide groups; despite this structural variation, meristem function during organogenesis and stem cell renewal is conserved. Major evolutionary innovations in shoot development include the dominance of the sporophyte generation over the gametophyte, and the emergence of multicellular shoot apical meristems that produce photosynthetic leaves. In this project, analyses of gene expression networks in plant shoot apices will identify shared and unique mechanisms for apical meristematic development among the ancient gametophyte-dominant model bryophytes Marchantia polymorpha and Physcomitrella patens, and the recently evolved sporophyte-dominant angiosperms Zea mays and Arabidopsis thaliana. Laser-microdissection coupled with RNA-sequencing will compare shoot apical transcriptomic signatures from these diverse model plants. Three categories of candidate gene will be identified: (1) functionally shared transcripts among the gametophyte meristems or lateral organs of the bryophytes and the sporophyte meristem or lateral organ of maize and Arabidopsis; (2) sporophyte-specific transcripts among the four model organisms, and; (3) transcripts unique to each lineage and domain. All data generated during this project will be released to public databases, including the TRANSCRIPTOME link at the CosMoss database for Physcomitrella patens, and the Marchantia polymorpha database at the DOE Joint Genome Institute. This project also will provide training in genomic analyses and mechanisms of plant development for a Cornell University Plant Biology graduate student.