Hydroxyproline-rich glycoproteins are involved in cotton fiber development

Functional Genomics

poster

xu, wenliang; Li, Xuebao

xu, wenliang

Li, Xuebao

Hydroxyproline-rich glycoproteins (HRGPs) contribute to cell wall structure of specific cell types and are involved in plant growth and development. In this study, a fiber-specific gene, GhPRP5, encoding a proline-rich protein was functionally characterized in cotton. GhPRP5 promoter directed GUS expression only in trichomes of both transgenic Arabidopsis and tobacco plants. The transgenic Arabidopsis plants with overexpressing GhPRP5 displayed reduced cell growth, resulting in smaller cell size and consequently plant dwarfs, in comparison to wild-type plants. In contrast, knock-down of GhPRP5 expression by RNA interference in cotton enhanced fiber development. The fiber length of transgenic cotton lines was longer than that of wild type. In addition, a number of genes that are involved in the cell wall-plasma membrane (PM)-cytoskeleton continuum were up-regulated or down-regulated in the transgenic cotton plants owing to suppression of GhPRP5. In addition, a fasciclin-like arabinogalactan protein gene (GhFLA1) was identified in cotton. Overexpression of GhFLA1 in cotton promoted fiber elongation, leading to an increase in fiber length. In contrast, suppression of GhFLA1 expression in cotton slowed down fiber initiation and elongation. As a result, the mature fibers of the transgenic plants were significantly shorter than those of the wild type. Moreover, expression levels of GhFLAs and the genes related to primary cell wall biosynthesis were remarkably enhanced in the GhFLA1 overexpression transgenic fibers, whereas the transcripts of these genes were dramatically reduced in the fibers of GhFLA1 RNA interference plants. An immunostaining assay indicated that both AGP composition and primary cell wall composition were changed in the transgenic fibers. Together, our results suggested that PRPs and AGPs function in fiber initiation and elongation.