Abstract 2202 β-Amylase9 is a stress-induced pseudoenzyme that binds to and activates ɑ-amylase3 to facilitate plant starch degradation

Starch accumulation in plants provides carbon for nighttime use, for regrowth after periods of dormancy, and for times of stress. Both ɑ- and β-amylases (AMYs and BAMs, respectively) catalyze starch hydrolysis. The Arabidopsis genome contains three AMY genes and nine BAM genes, but many of their functional roles are unclear. Moreover, the presence of catalytically inactive BAMs that show starch excess phenotypes when deleted presents questions on how starch degradation is regulated. One of these catalytically inactive amylases, BAM9, is conserved in all flowering plants and is located in chloroplasts with starch.