The cotton β‐galactosyltransferase 1 (GalT1) that galactosylates arabinogalactan proteins participates in controlling fiber development

Abstract

Arabinogalactan proteins (AGPs) are highly glycosylated proteins that play pivotal roles in diverse developmental processes in plants. Type-II AG glycans, mostly O-linked to the hydroxyproline residues of the protein backbone, account for up to 95% w/w of the AGP, but their functions are still largely unclear. Cotton fibers are extremely elongated single-cell trichomes on the seed epidermis; however, little is known of the molecular basis governing the regulation of fiber cell development. Here, we characterized the role of a CAZy glycosyltransferase 31 (GT31) family member, GhGalT1, in cotton fiber development. The fiber length of the transgenic cotton overexpressing GhGalT1 was shorter than that of the wild type, whereas in the GhGalT1-silenced lines there was a notable increase in fiber length compared with wild type. The carbohydrate moieties of AGPs were altered in fibers of GhGalT1 transgenic cotton. The galactose: arabinose ratio of AG glycans was higher in GhGalT1 overexpression fibers, but was lower in GhGalT1-silenced lines, compared with that in the wild type. Overexpression of GhGalT1 upregulates transcript levels of a broad range of cell wall-related genes, especially the fasciclin-like AGP (FLA) backbone genes. An enzyme activity assay demonstrated that GhGalT1 is a β-1,3-galactosyltransferase (β-1,3-GalT) involved in biosynthesis of the β-1,3-galactan backbone of the type-II AG glycans of AGPs. We also show that GhGalT1 can form homo- and heterodimers with other cotton GT31 family members to facilitate AG glycan assembly of AGPs. Thus, our data demonstrate that GhGalT1 influences cotton fiber development via controlling the glycosylation of AGPs, especially FLAs.

The cotton (Gossypium hirsutum) NAC transcription factor (FSN1) as a positive regulator participates in controlling secondary cell wall biosynthesis and modification of fibers

“…The surface of mature fibers was examined by cold‐field scanning electron microscopy (Hitachi) after dehydration and platinum spraying. Additionally, resin‐embedded cross‐sections of 30 DPA fibers were observed and photographed under a light microscope as described previously (Qin et al ., ).…”

Plant carbohydrate‐active enzymes in bamboo Neosinocalamus affinis: identification, classification and function in lignocellulose biosynthesis in herbivore defence

“…F); this gene encodes a galactosyltransferase for arabinogalactan protein galactosylation during backbone formation (Henrissat et al ). A novel GT31 gene, GhGalT1 , participates in the regulation of cell wall pectin biosynthesis during plant development (Qin et al ) and the control of fibre development (Qin et al ) in cotton. In plants, the GT43 family is a large CAZyme family, and 10 candidate genes were identified in the N. affinis transcriptome (Fig.…”

Tissue-Specific Transcriptome Analysis Reveals Lignocellulose Synthesis Regulation in Elephant Grass (Pennisetum purpureum Schum.)

“…In tobacco, it was reported that the sense or antisense expression of sequences encoding O-methyltransferase (OMT) could regulate enzyme activity of lignin synthesis [51]. The ber length of transgenic cotton overexpressing GhGalT1 was shorter than that of wild type, while in GhGalT1 silenced line, the ber length was signi cantly increased than that of wild type [52].…”