Discovery of Novel Genes Regulating Polysaccharide Biosynthesis and Secretion in Plants

During cotton ovule development there is a rapid burst in the secretion and deposition of non-cellulosic cell wall polymers between 4 and 6 days post-anthesis (dpa). Within this developmental time period, the cotton Golgi swell and produce a large number of secretory vesicles to accommodate the increase in secretion. Differential proteomics of cotton Golgi at 4 and 6 dpa has generated an extensive list of ~800 proteins that increase in abundance and are hypothetically involved in non-cellulosic cell wall biosynthesis and/or secretion. While many of these 6dpa abundant proteins are already known to be involved in polysaccharide biosynthesis and secretion (i.e. nucleotide sugar interconverting enzymes, glycosyltransferases, and transport related proteins), most have been annotated as genes of unknown function. To identify novel proteins which facilitate and/or modulate polysaccharide transport, we have selected a subset of these 6dpa abundant unknown proteins. Currently, we have cloned seventeen Arabidopsis orthologs of these cotton candidates as cerulean cyan fluorescent protein fusions; fifteen of which have been localized to endomembranes by transient expression analyses followed by live cell imaging. t-DNA insertion lines have been identified for many of these candidates, and preliminary analyses show several lines having altered cell wall and/or growth phenotypes. This research puts sound foundations toward establishing the nature of factors that not only control cell wall biosynthesis, but also the traffic of cell wall components through and from the Golgi apparatus.