Golgi enzymes that synthesize plant cell wall polysaccharides: finding andevaluating candidates in the genomic era

Although the synthesis of cell wall polysaccharides is a critical process d uring plant cell growth and differentiation, many of the wall biosynthetic genes have not yet been identified. This review focuses on the synthesis of non-cellulosic matrix polysaccharides formed in the Golgi apparatus. Our c onsideration is limited to two types of plant cell wall biosynthetic enzyme s: glycan synthases and glycosyltransferases. Classical means of identifyin g these enzymes and the genes that encode them rely on biochemical purifica tion of enzyme activity to obtain amino acid sequence data that is then use d to identify the corresponding gene. This type of approach is difficult, e specially when acceptor substrates for activity assays are unavailable, as is the case for many enzymes. However, bioinformatics and functional genomi cs provide powerful alternative means of identifying and evaluating candida te genes. Database searches using various strategies and expression profili ng can identify candidate genes. The involvement of these genes in wall bio synthesis can be evaluated using genetic, reverse genetic, biochemical, and heterologous expression methods. Recent advances using these methods are c onsidered in this review.