Location: Hard Winter Wheat Genetics ResearchTitle: Presence of tannins in sorghum grains is conditioned by different natural allels of Tannin1) Author
Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2012
Publication Date: 6/13/2012
Publication URL: www.polosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0037573
Citation: Wu, Y., Li, X., Xiang, W., Zhu, C., Lin, Z., Wu, Y., Li, J., Pandravada, S., Ridder, D., Bai, G., Wang, M.L., Trick, H., Bean, S., Tuinstra, M., Tesso, T., Yu, J. 2012. Presence of tannins in sorghum grains is conditioned by different natural allels of Tan1. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1201700109/-/DCSupplemental. Interpretive Summary: Sorghum is an ancient cereal crop and a staple crop that feeds over 500 million people in more than 30 countries. It has drought resistance, wide adaptation, and high nutritional value and also is an energy crop. Condensed tannins in the pigmented seed coat of some sorghum cultivars may promote human health due to their high antioxidant capacity and ability to reduce obesity through reduced digestion. We cloned and verified the function of the gene, Tan1, that controls tannin biosynthesis in sorghum. This research opens the possibility of manipulating the levels and combinations of phenolic compounds in sorghum to promote better human health.
Technical Abstract: Sorghum, an ancient old-world cereal grass, is the dietary staple of over 500 million people in more than 30 countries in the tropics and semi-tropics. Its C4 photosynthesis, drought resistance, wide adaptation, and high nutritional value hold the promise to alleviate hunger in Africa. Not present in other major cereals such as rice, wheat, and maize, condensed tannins (proanthocyanidins) in the pigmented testa of some sorghum cultivars have been implicated in reducing protein digestibility, but recently have been shown to promote human health because of their high antioxidant capacity and ability to fight obesity through reduced digestion. Combining quantitative trait locus (QTL) mapping, meta-QTL fine-mapping, and association mapping, we showed that the nucleotide polymorphisms in the Tan1 gene, coding a WD40 protein, control the tannin biosynthesis in sorghum. A 1-bp G deletion in the coding region, causing a frame shift and a premature stop codon, led to a nonfunctional allele, tan1-a. Likewise, a different 10-bp insertion resulted in a second nonfunctional allele, tan1-b. Transforming the sorghum Tan1 ORF into a non-tannin Arabidopsis mutant restored the tannin phenotype. In addition, reduction in nucleotide diversity from wild sorghum accessions to landraces and cultivars was found at the region that codes the highly conserved WD40 repeat domains and the C-terminal of the protein. Genetic research in crops coupled with nutritional and medical research could open the possibility of producing different levels and combinations of phenolic compounds to promote human health.