OsVTC1-1 RNAi Mutant with Reduction of Ascorbic Acid Synthesis Alters Cell Wall Sugar Composition and Cell Wall-Associated Proteins

Abstract

Ascorbic acid (AsA) or Vitamin C is an antioxidant molecule and plays an important role in many biological processes in plants. GDP-D-mannose pyrophosphorylase (GMP or VTC1) catalyzes the synthesis of GDP-D-mannose, which is a precursor for AsA production and is used for cell wall polysaccharide and glycoprotein synthesis. In rice, the OsVTC1 gene consists of three homologs, including OsVTC1-1, OsVTC1-3 and OsVTC1-8. In this study, we characterized wild type (WT) and OsVTC1-1 RNAi lines (RI1-2 and RI1-3) and showed that the transcript levels of most genes in the AsA synthesis pathway, AsA content and leaf anatomical parameters in RNAi lines were reduced, revealing that OsVTC1-1 is involved in AsA synthesis. To further study the role of OsVTC1-1 gene, cell wall monosaccharide composition, transcriptome and proteome were compared, with specific attention paid to their wild type and OsVTC1-1 RNAi lines. Mannose and galactose composition (mole%) were decreased in OsVTC1-1 RNAi lines. Additionally, reduction of cell wall-associated proteins, such as kinesin, expansin, beta-galactosidase and cellulose synthase were observed in OsVTC1-1 RNAi lines. Our results suggest that OsVTC1-1 gene plays an important role in AsA synthesis and in cell wall-related processes.