4-04: Discovery of genes that mediate and regulate hemicellulose biosynthesis

One attractive strategy for identifying the required genes is to perform expression profiling during periods of rapid hemicellulose deposition.  Many plants produce large quantities of specific polysaccharides as storage polymers in developing seeds. Earlier studies of these seed systems has been used to identify proteins involved in mannan and xyloglucan biosynthesis.  We are extending these earlier studies by using 454 sequencing technology to perform deep EST sequencing at various stages of seed development during and just before rapid synthesis of mannan (Fenugreek-Trigonella foenum-graecum), xyloglucan (Nasturtium-Tropaeolum majus), or arabinoxylan (Psyllium-Plantago ovata).   Analysis of the sequences obtained has confirmed the expression of genes known to be involved in the biosynthesis of these polysaccharides.  In addition, a number of other genes have emerged as strong candidates for involvement in the production of these polysaccharides or in regulation of these pathways.  Among the candidates that have been identified are putative sugar nucleotide biosynthetic enzymes, putative sugar nucleotide transporters, putative and known glycosyltransferases and glycan synthases, proteins of unknown function, and transcription factors.  Many of the genes have homologs that are expressed in developing wood or in other plant tissues where secondary wall synthesis is occurring rapidly, providing support for the hypothesis that the same genes are involved in depositing these polymers in secondary cell walls.  Promising examples from each class of candidate genes have been selected for detailed functional analysis. Selected examples from each polysaccharide will be presented on the poster.