Functional Analysis of LEAFY Homologs in the Fern Ceratopteris richardii

Undergraduate #136
Discipline: Biological Sciences
Subcategory: Plant Research

Jonathan Yee - University of Washington
Co-Author(s): Kristen Hazelton and Veronica Di Stilio, University of Washington, Seattle, WA

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This research explores the ancestral role of developmental genes in the evolution of land plants. In flowering plants, LEAFY (LFY) is a master regulator of flower development, turning on the floral organ identity genes during sporophyte reproduction. A loss-of-function mutant of a LFY ortholog of the moss Physcomitrella patens shows an earlier role of this gene in the first cell division of the zygote, during sporophyte early development. The immense phylogenetic distance between mosses (non-vascular plants) and flowering plants and the starkly different functions of LFY in these two land plants, begs the question of what is the role of LFY homologs in other vascular plants. To that end we turned to the model fern Ceratopteris richardii, a representative of an earlier vascular plant lineage and the sister group to seed plants. For this study, we used loss-of-function trasngenics to determine the role of two LFY orthologs from fern (CrLFY1 and CrLFY2). The approach will use RNA interference (RNAi) constructs that will reduce the expression of the two genes individually and together. This transgenic approach will help determine whether these homologs have unique, redundant, or complementary functions in C. richardii and how their function compares to that of other land plants. Transgenic plants were generated by particle bombardment of callus followed by tissue culture, and selected for antibiotic resistance. Molecular validation is carried out by Polymerase chain reaction followed by gene expression analysis in positive lines, to confirm the down-regulation of the targeted gene/s. Phenotypic characterization of confirmed lines is currently under way Future directions include a complementary overexpression approach and the elucidation of the CrLFY gene regulatory network. Finally, we will place our developmental work back in an evolutionary context by comparing and contrasting LFY function across the land plant phylogeny and reconstructing its putative role in the seed plant ancestor.

Funder Acknowledgement(s): NIH 5R25HG007153-03, Anne Dinning, Michael Woolf

Faculty Advisor: Veronica Di Stilio,