Changes in α-xylosidase during intact and auxin-induced growth of pine hypocotyls

Abstract

A complete cDNA from Pinus pinaster Aiton, potentially coding for an α-xylosidase able to remove the xylose residue from xyloglucan oligosaccharides, has been cloned. Its sequence was homologous to previously published α-xylosidase genes from Arabidopsis and nasturtium. The protein also showed the two signature regions of family 31 of glycosyl hydrolases. The gene expression level was quantified by competitive RT-PCR, under different growth conditions, throughout seedling development, in different regions along the hypocotyls and in auxin-treated hypocotyl segments, and related with growth capacity and α-xylosidase activity. A role of α-xylosidase in regulating the level of xyloglucan oligosaccharides within the apoplast is proposed. The action of an α-xylosidase removing the xylose residue, would make possible the action of a β-glucosidase deblocking the xyloglucan oligosaccharide degradation and it could serve as a control point for the regulation of the apoplastic levels of xyloglucan oligosaccharides.