Location: Tropical Crops and Germplasm ResearchTitle: Seed shattering in a wild sorghum is conferred by a locus unrelated to domestication Author
Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2013
Publication Date: 9/10/2013
Citation: Tang, H., Cuevas, H.E., Das, S., Sezen, U.U., Guo, H., Goff, V.H., Clemente, T.E., Patterson, A.H. 2013. Seed shattering in a wild sorghum is conferred by a locus independent of a domestication locus. Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1305213110. Interpretive Summary: A key step during crop domestication of sorghum is the loss of seed shattering. Herein, we demonstrated that the SpWRKY gene confers shattering to a wild sorghum relative, Sorghum propinquum. This gene regulates cell wall biosynthesis by allowing deposition of lignin in the seed-pedicel junction to initiate seed abscission. The understanding of key domestication traits in wild relative species of sorghum allows the incorporation of this exotic germplasm into breeding programs. Genetic markers for this shattering allele can be developed and used as an important tool in marker assisted selection to introgress economically important genes from wild relatives into improved sorghum germplasm.
Technical Abstract: Suppression of seed shattering was a key step during crop domestication that we have previously suggested to be convergent among independent cereal lineages. Positional, association, expressions and mutant complementation data all implicated a WRKY transcription factor, SpWRKY, in conferring shattering to a wild sorghum relative, S. propinquum. We hypothesize that SpWRKY functions in a manner analogous to Medicago and Arabidopsis homologs that regulate cell wall biosynthesis genes, with low expression toward the end of floral development de-repressing downstream cell wall biosynthesis genes to allow deposition of lignin that initiates the abscission zone in the seed-pedicel junction. The recent discovery of a YABBY locus that confers shattering within S. bicolor and other cereals validates our prior hypothesis that some parallel domestications may have been convergent. Ironically, however, the shattering allele of SpWRKY appears to be recently-evolved in S. propinquum and illustrates a case in which the genetic control of a trait in a wild relative fails to extrapolate even to closely-related crops. Remarkably, the SpWRKY and YABBY loci lie only 300 kb apart, and may have appeared to be a single genetic locus in some sorghum populations.