Ancient genome duplications and glucosinolate evolution in the Brassicales

Understanding the role of ancient whole genome duplications (WGD) and subsequent pathway divergence in generating the complexity of life on earth is an important goal of comparative genomics. Recent genomic analyses have found that most angiosperm lineages have had one to several rounds of WGD. These WGDs are believed to have contributed to plant evolutionary innovations and success. However, there are few examples of how innovations derive from duplicated pathways. We seek to illustrate the potential link between WGDs and key-trait evolution by investigating the glucosinolate defense pathway in the plant order Brassicales. The Brassicales has a wealth of genomic data, a well-characterized WGD ancestry and detailed ecological data on glucosinolate defense compounds. There are two lines of support for why the divergence of glucosinolates might be coupled to WGDs. The first indication is from the phylogeny. The appearance of indole glucosinolates coincides with one WGD shared by around half of the Brassicales, whereas the Met-derived compounds coincide with a second WGD of the Brassicaceae. Secondly, we have found that many glucosinolate genes are paralogs attributable to WGD. To further investigate the role of WGDs on the evolution of glucosinolates we propose to: make a detailed survey of glucosinolates and correlated metabolites, identify homologous genes from Brassicales genomic and EST sequences, bioinformatically look for evidence of duplication and divergence of genes, perform targeted gene expression analysis and finally integrate all findings to understand pathway divergence(s). This work will provide great insights into the role of WGDs in driving diversification and the evolution of a key ecological innovation.