Parallel Domestication of the Sh1 Genes in Cereals.

Cereal crops, the primary calorie source for humans, were domesticated thousands of years ago. A key step during crop domestication is the loss of seed shattering. Here we show that seed shattering in sorghum is controlled by a single gene, SHATTERING1 (Sh1), which encodes a YABBY transcription factor. Domesticated sorghums harbor three different mutations at the Sh1 locus. Variants at regulatory sites in the promoter and intronic regions lead to a low level of expression, a 2.2-kb fragment deletion causes a truncated transcript that lacks the second and third exons, and a “GT” to “GG” splicing variant in the fourth intron removes the fourth exon. The distributions of these non-shattering haplotypes among sorghum landraces suggest three independent origins. The function of the rice ortholog (OsSh1) was subsequently validated with a shattering resistant mutant, and two maize orthologs (ZmSh1-1 and ZmSh1-5.1+ZmSh1-5.2) were verified with a large mapping population. Our results indicate that Sh1 genes for seed shattering were under parallel selection during sorghum, rice, and maize domestication.