Colloquia

         Attack of the (haploid) clones: the resurgence of gametophyte biology across land plants

Exploring the fern life cycle: gene expression patterns between gametophytes and sporophytes and sex determination in ferns

Presenting Author
Emily Kim
Description
Ferns, like all land plants, have diploid sporophyte and haploid gametophyte life phases. However, they are unique in that the large, leafy sporophytes and reduced gametophytes are nutritionally independent. The mechanism that drives these morphological and functional disparities, including sexual differentiation in gametophytes, is unknown. It is largely unexplored despite the crucial role that the gametophyte plays in the fern life cycle, as the gametophyte is the site of sexual reproduction. Studies using Ceratopteris (Pteridaceae) and Polypodium (Polypodiaceae) explored differential gene expression (DGE) between sporophytes and gametophytes and proposed that alternative splicing (AS) may contribute to expression differences. To start unraveling the genetic underpinnings that drive these differences, we will investigate DGE and AS in Dryopteris ludoviciana (Dryopteridaceae). Sporophytes from a population in Gainesville were collected and acclimated to greenhouse conditions at the University of Florida. Spores from these samples will be grown in the same conditions to sexual maturity, marked by the development of gametangia. RNA will be extracted from newly developing fronds and gametophytes to sequence nine RNA libraries (three sporophytes, three male gametophytes, three female gametophytes). A reference transcriptome will be de novo assembled using these libraries and reads will be mapped to the reference to analyze DGE and AS. We will also perform a functional annotation of the transcriptome to determine the functions of the differentially expressed genes and AS events. To place this work in a greater phylogenetic context, we will compare D. ludoviciana to other ferns and land plants by comparing the expression and splicing of orthologous gene families among ferns and various land plants across the phylogeny. The results of this project will contribute to the understanding of genetic underpinnings driving differentiation of sporophytes and gametophytes and sexual determination across land plants.