Co-Overexpression of Two Key Source Genes, <i>OsBMY4</i> and <i>OsISA3</i>, Improves Multiple Key Traits of Rice Seeds

Abstract

Optimized source-sink interactions are determinants of both rice yield and quality. However, most source genes have not been well studied in rice, a major grain crop. In this study, OsBMY4 and OsISA3, the key β-amylase and debranching enzymes that control transient starch degradation in rice leaves, were co-overexpressed in rice in order to accelerate starch degradation efficiency and increase the sugar supply for sink organs. Systematic analyses of the transgenic rice indicated that co-overexpression of <i>OsBMY4</i> and <i>OsISA3</i> not only promoted rice yield and quality, but also improved seed germination and stress tolerance. Moreover, since the <i>OsBMY4</i> gene has not been characterized, we generated <i>osbmy4</i> mutants using CRIPSR/Cas9 gene editing, which helped to reveal the roles of β-amylase in rice yield and quality. This study demonstrated that specific modulation of the expression of some key source genes improves the source-sink balance and leads to improvements in multiple key traits of rice seeds.