AP2-like transcription factor SUPERNUMERARY BRACT controls rice seed shattering and seed size (Plant Cell)

Non-shattering seed, or seed that stays attached to the stem when mature, is a key domestication trait that makes harvesting easier. Previous studies have identified several domestication genes that suppress the formation of the seed’s abscission zone, thus preventing shattering. Jiang et al. used a genetic approach to identify ssh1, which suppresses seed shattering; SSH1 encodes the AP2-type transcription factor SUPERNUMERARY BRACT (SNB). The development of the absission zone is positively correlated with SNB expression. Lignin deposition at the abscission zone is increased in the ssh1 mutant, and two genes previously identified as involved in seed shattering are downregulated in the ssh1 mutant; SNB likely is a direct transcriptional activator of these genes. Interestingly, the ssh1 mutant also has increased seed size and weight, which may arise due to other transcriptional targets, possibly involving hormones. This study provide new targets for engineering increased grain yields. (Summary by Mary Williams)  Plant Cell 10.1105/tpc.18.00304