Abstract
Intercellular attachment is an essential process in the morphogenesis of multicellular organisms. A novel mutant, nolac-H18 (non-organogenic callus with loosely attached cells), generated by T-DNA transformation using leaf-disk cultures of haploid Nicotiana plumbaginifolia, lost the ability to form tight intercellular attachments and adventitious shoots. The mutation caused defects in the glucuronic acid of rhamnogalacturonan II (RG-II) of pectin, which drastically reduced the formation of borate cross-linking of RG-II. The gene tagged with T-DNA, named NpGUT1 (glucuronyltransferase 1), which encodes a novel glucuronyltransferase, is the first glycosyltransferase gene identified in pectin biosynthesis and is essential for intercellular attachment in plant meristems and tissues (PNAS, in press). The GUS activity in transgenic tobacco plants with pNpGUT1::GUS was detected in immature embryo, cotyledon, phloem, vascular cambium, tapetum, pollen and pollen tube. These results indicate that these meristematic tissues and pollen are required for a high level of NpGUT1 expression.
