A Novel Isoform of Sucrose Synthase Is Targeted to the Cell Wall during Secondary Cell Wall Synthesis in Cotton Fiber

• DOI: 10.1104/pp.111.178574
• Publication Date: 2011-09-03T15:07:58Z
• Authors: Elizabeth Brill; Michel van Thournout; Rosemary G. White; Danny Llewellyn; Peter M. Campbell; Steven Engelen; Yong-Ling Ruan; Tony Arioli; Robert T. Furbank
• Keywords: 580; 0301 basic medicine; Gossypium; Sequence Homology, Amino Acid; Molecular Sequence Data; isoform; Genes, Plant; Isoenzymes; 03 medical and health sciences; cotton fiber; Cell Wall; Glucosyltransferases; Amino Acid Sequence; Cotton Fiber; RNA, Messenger; cellulose biosynthesis; sucrose synthase; Phylogeny; Plant Proteins; Subcellular Fractions

Abstract Sucrose (Suc) synthase (Sus) is the major enzyme of Suc breakdown for cellulose biosynthesis in cotton (Gossypium hirsutum) fiber, an important source of fiber for the textile industry. This study examines the tissue-specific expression, relative abundance, and temporal expression of various Sus transcripts and proteins present in cotton. A novel isoform of Sus (SusC) is identified that is expressed at high levels during secondary cell wall synthesis in fiber and is present in the cell wall fraction. The phylogenetic relationships of the deduced amino acid sequences indicate two ancestral groups of Sus proteins predating the divergence of monocots and dicots and that SusC sequences form a distinct branch in the phylogeny within the dicot-specific clade. The subcellular location of the Sus isoforms is determined, and it is proposed that cell wall-localized SusC may provide UDP-glucose for cellulose and callose synthesis from extracellular sugars.