Genetic manipulation of rice OsERF071 alters plant growth and grain yield via regulation of secondary cell wall deposition in stems.

Abstract

Characterization of the complex hierarchical networks of Transcription Factors (TFs) that regulate plant cell wall deposition have been shown to influence plant development and responses to environmental stimuli. However, most of these TFs are associated with secondary cell wall (SCW) deposition, and significant gaps remain in our understanding of the regulatory mechanisms of primary cell wall (PCW) deposition and the transition from PCW to SCW deposition during cell development. Using gene association networks analysis in rice, five TFs co-expressed with cellulose synthesis (OsCESAs) genes and heteroxylan synthesis genes (members of OsGT43 and OsGT47 families) were identified. The focus of this work is the characterization of one of them, namely, OsERF071 from the AP2-ERF family, through characterization of loss-of-function allelic mutants and overexpression lines. Both allelic mutants were slightly taller compared to controls, including larger panicles and seeds, increased thousand grain weights, and increased aboveground yields. Additionally, the allelic mutants exhibited higher expression levels of OsCESA genes related to SCW deposition, but the expression of OsCESA genes linked to PCW biosynthesis was unchanged, which agrees with higher lignin and cellulose contents in the xylem of the inflorescence stem of allelic mutants. In contrast, overexpression lines showed opposite phenotypes (shorter plants, less lignin and cellulose contents). Our results suggest that OsERF071 may function as a repressor of SCW deposition in growing stem tissues, which sheds light on the role of this TF in regulating plant development and cell wall biosynthesis and offers a mechanism to increase plant biomass and grain yield.