Multi-Tissue Transcriptome Analysis of Two Begonia Species Reveals Dynamic Patterns of Expression Evolution In The Chalcone Synthase Gene Family

Abstract Begonia is an important horticultural plant, as well as one of the most speciose Angiosperm genera, with over 2000 described species. Genus wide studies of genome size have shown that Begonia has a highly variable genome size, and analysis of paralog pairs has previously suggested that Begonia underwent a whole genome duplication. We address the contribution of gene duplication to the generation of diversity in Begonia using a multi-tissue RNA-seq approach. We chose to focus on the chalcone synthase (CHS) gene family due to its role in biotic and abiotic stress response, and in particular its importance in maximising the use of variable light levels in tropical plants. We used RNA-seq to sample six tissues across two closely related but ecologically and morphologically divergent species, Begonia conchifolia and B. plebeja, yielding 17,012 and 19,969 annotated unigenes respectively. We identified the chalcone synthase gene family members in our Begonia study species, as well as in Hillebrandia sandwicensis, the monotypic sister genus to Begonia, Cucumis sativus, Arabidopsis thaliana, and Zea mays. Phylogenetic and expression analysis revealed the recent origin of CHS duplicates in Begonia, which showed both conserved and divergent expression profiles between duplicates. We conclude that there is evidence for a role of gene duplication in generating diversity through expression divergence in Begonia.