GENE DISCOVERY IN THE WOOD-FORMING TISSUES OF POPLAR - ANALYSIS OF 5,692 EXPRESSED SEQUENCE TAGS

A rapidly growing area of genome research is the generation of express ed sequence tags (ESTs) in which large numbers of randomly selected cD NA clones are partially sequenced. The collection of ESTs reflects the level and complexity of gene expression in the sampled tissue, To dat e, the majority of plant ESTs are from nonwoody plants such as Arabido psis, Brassica, maize, and rice. Here, we present a large-scale produc tion of ESTs from the wood-forming tissues of two poplars, Populus tre mula L, x tremuloides Michx, and Populus trichocarpa 'Trichobel.' The 5,692 ESTs analyzed represented a total of 3,719 unique transcripts fo r the two cDNA libraries, Putative functions could be assigned to 2,24 5 of these transcripts that corresponded to 820 protein functions. Of specific interest to forest biotechnology are the 4% of ESTs involved in various processes of cell wall formation, such as lignin and cellul ose synthesis, 5% similar to developmental regulators and members of k nown signal transduction pathways, and 2% involved in hormone biosynth esis. An additional 12% of the ESTs show ed no significant similarity to any other DNA or protein sequences in existing databases. The absen ce of these sequences from public databases may indicate a specific ro le for these proteins in wood formation. The cDNA libraries and the ac companying database are valuable resources for forest research directe d toward understanding the genetic control of wood formation and futur e endeavors to modify wood and fiber properties for industrial use.