Inflorescences
Genetic Basis of Inflorescence Diversification in Millet Grasses
I am examining the genetic basis of differences in inflorescence architecture using a cross between two species of Setaria. The two species are the weed green millet (Setaria viridis) and its domesticated form foxtail millet (S. italica). These differ markedly in size and branching in the inflorescence. These characters also vary across the millet grasses, so we hope that identifying genes controlling differences in inflorescence architecture between green and foxtail millet will help us understand the genetics underlying the morphological diversification of the group as a whole. I use quantitative trait loci (QTL) analysis to correlate genomic variation (measured by variable RFLP and PCR markers that are arranged into a genetic linkage map) with variation in inflorescence traits such as number of branches, and how many of the branches eventually initiate spikelets or sterile bristles. Once regions of significant correlation (QTL) have been identified, I use the high degree of similarity in gene identity and order between linkage groups amongst the grasses to identify likely candidate genes from maize and rice that that are in the same relative genomic regions as the QTL in Setaria. This has identified suites of genes that are now being evaluated further through association analyses in a new mapping population and through expression analysis. Some of the important genes are orthologues of knotted1, leafy, ramosa1, teosinte branched1, etc., and a mixture of conserved and novel patterns of expression suggest that their function has evolved in the grasses. I am also very interested in, and have preliminary data for, a parallel study of domestication in pearl millet (Pennisetum glaucum), where I can examine whether the same candidate genes are predicted for similar changes in inflorescence morphology.
Collaborators: Katrien Devos, University of Georgia, Athens; members of the Maize Inflorescence Diversity Consortium - Bob Schmidt, University of California at San Diego; Sarah Hake, University of California at Berkeley; Paula MacSteen, Pennsylvania State University, College Park; Torbert Rocheford, University of Illinois, Urbana-Champagne, Erik Vollbrecht, Iowa State University, Ames; Simon Malcomber, Elizabeth Kellogg, University of Missouri-St. Louis.