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, 2002). The GUS activity in pNpGUT1::GUS transgenic tobacco plants was detected in embryo, cotyledon, phloem, tapetum, pollen, pollen tube and transmitting tissue of pistil. These results suggest that these tissues require the borate cross-linking of pectin RG-II.
