Extensin arabinoside chain length is modulated in elongating cotton fibre

Cotton fibre provides a unicellular model system for studying cell expansion and secondary cell wall deposition. Mature cotton fibres are mainly composed of cellulose while the walls of developing fibre cells contain a variety of polysaccharides and proteoglycans required for cell expansion. This includes hydroxyproline-rich glycoproteins (HRGPs) comprising the subgroup, extensins. In this study, extensin occurrence in cotton fibres was assessed using carbohydrate immunomicroarrays, mass spectrometry and monosaccharide profiling. Extensin amounts in three species appeared to correlate with fibre quality. Fibre cell expression profiling of the four cotton cultivars, combined with extensin arabinoside chain length measurements during fibre development, demonstrated that arabinoside side-chain length is modulated during development. Implications and mechanisms of extensin side-chain length dynamics during development are discussed.

Keywords: AGPs, arabinogalactan proteins; CoMPP; CoMPP, comprehensive microarray polymer profiling; Cotton fibre; Cotton fibre quality; CrRLK1L, Catharanthus roseus receptor-like1-like kinase; DPA, days post anthesis; EXTs, extensins; ExAD, arabinosyltransferase named after the mutant Extensin Arabinose Deficient; Extensin arabinoside metabolism; GH, glycoside hydrolase; HPAT, hydroxyproline arabinosyltransferase; HRGP; HRGPs, hydroxyproline-rich glycoproteins; Hyp-Aran, extensin side-chain of length n; LRX, leucine-rich repeat extensins; PCW, primary cell wall; RRA, arabinosyltransferase named after the mutant Reduced Residual Arabinose; SCW, secondary cell wall; SGT, serine galactosyltransferase; Transcriptomics; XEG113, arabinosyltransferase named after the mutant Xyloglucan Endo-Glucanase resistant mutant 113.