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

Cornell University, Ithaca NY

Investigators

Abstract

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.