Expression and localization of GhH6L, a putative classical arabinogalactan protein in cotton (Gossypium hirsutum)

Arabinogalactan proteins (AGPs) are a large family of highly glycosylated of hydroxyproline-rich glycoproteins that play important roles in plant growth, development, and signal transduction. A cDNA encoding a putative classical AGP named GhH6L was isolated from cotton fiber cDNA libraries, and the deduced protein contains 17 copies of repetitive motif of X-Y-proline-proline-proline (where X is serine or alanine and Y is threonine or serine). Northern blotting analysis and quantitative RT-PCR results showed that it was preferentially expressed in 10 days post-anthesis (dpa) fibers and was also developmentally regulated. A promoter fragment was isolated from cotton (Gossypium hirsutum) by genome walking PCR. Expression of beta-glucuronidase (GUS) gene under the GhH6L promoter was examined in the transgenic Arabidopsis plants; only petiole and pedicel were stained, no staining was detected in other tissues. Subcellular localization indicated that GhH6L was localized to the plasma membrane and in the cytoplasm. These data further our understanding of GhH6L as well as shed light on functional insight to GhH6L in cotton.