Abstract

Conical-shaped or papillate epidermal cells, found on the petals of many flowering plants, have been shown to facilitate pollination and thus increase plant fitness in a variety of ways, including through colour enhancement and improved pollinator grip. MIXTA genes (encoding members of the R2R3 MYB transcription factor family) have previously been implicated in the development of these specialised cells in various angiosperms, including Antirrhinum and Arabidopsis. My focus is on the function and evolution of MIXTA homologues at both the microevolutionary scale, in the angiosperm genus Nicotiana, and at the macroevolutionary level, utilising the model bryophyte species Marchantia polymorpha and Physcomitrella patens. The broad aims of my research are twofold. Firstly, by investigating MIXTA genes within Nicotiana, a genus that contains species both with and without conical cells, I will explore how their expression patterns and functions are linked to evolutionary changes in epidermal cell morphology. Second, by studying the function of MIXTA homologues in early divergent land plant lineages (Bryophyta and Marchantiophyta), I seek to gain insight into the ancestral function(s) of the MIXTA genes.