CEF3 is involved in membrane trafficking and essential for secondary cell wall biosynthesis and its mutation enhanced biomass enzymatic saccharification in rice.

Background: As one of the most important staple food crops, rice produces large of agronomic biomass residues that contain lots of secondary cell walls (SCWs). Membrane trafcking plays key roles in SCWs biosynthesis, but information association membrane trafcking and SCWs formation in plants is limited. Results: In this study, we report the function characterization of a rice mutant, culm easily fragile 3 (cef3), that exhibits growth retardation and fragile culm phenotype with signifcantly altered cell wall composition and reduced second-ary wall thickness. Map-based cloning revealed that CEF3 encodes a homologous protein of Arabidopsis STOMATAL CYTOKINESIS DEFECTIVE2 (SCD2). The saccharifcation assays revealed that CEF3 mutation can improve biomass enzymatic saccharifcation. Expression pattern analysis indicated that CEF3 is ubiquitously expressed in many organs at diferent developmental stages. Subcellular localization revealed that CEF3 is a Golgi-localized protein. The FM4-64 uptake assay revealed CEF3 is involved in endocytosis. Furthermore, mutation of CEF3 not only afected cellulose synthesis-related genes expression, but also altered the abundance of cellulose synthase catalytic subunit 9 (OsC-ESA9) in the PM and in the endomembrane systems. Conclusions: This study has demonstrated that CEF3 participates in the membrane trafcking that is essential for normal cellulose and other polysaccharides biosynthesis of the secondary cell wall, thereby manipulation of CEF3 could alter cellulose content and enhance biomass enzymatic saccharifcation in rice plants. Therefore, the study of the function of CEF3 can provide a strategy for genetic modifcation of SCWs in bioenergy crops. [ABSTRACT FROM AUTHOR]