Wood accounts for 25% of the value of all industrial materials produced in the U.S., and on an annual basis, the value of wood-derived products equals or exceeds that of virtually every other agricultural crop. However, losses in production forest acreage, coupled with increasing demands for paper and cheap fiber supplies from overseas, have put intense pressure on U.S. companies to increase wood yields per acre, particularly in southeastern forests. Unfortunately, our limited understanding of tree biology constitutes a significant barrier to attaining the productivity gains necessary to keep pace with the rising consumer demand for wood products. Efforts are underway to catalog genes expressed in the wood-forming tissues of loblolly pine (Pinus taeda), the predominant commercial tree species in the southeastern U.S. Although this collection of wood-specific genes provides an excellent step toward improved understanding of the basic genetic units governing wood formation, it will be incomplete with respect to many genes that will prove critical for increasing the productivity of tomorrow's forests. This project will develop a collection of several thousand new genes derived primarily from other pine tissues of commercial and biological significance, in particular roots undergoing a variety of biotic and abiotic stresses. To the greatest extent possible, data from this project will be integrated with that from other projects focused on genomic studies of pine so as to create a seamless set of resources, such as a comprehensive unigene set, for the research community. Such comprehensive unigene sets will form the basis of DNA microarrays that will be used to identify genes whose expression varies in response to various environmental and developmental cues, particularly those responding to stresses that trees would likely experience when subjected to intensive management regimes. Identification of such genes will provide for better understanding of the molecular mechanisms trees use to respond to environmental and biological stresses, and will enable the development of techniques and tools, such as targeted microarrays, that could be used to monitor in near real-time the effects of silvicultural practices on tree growth and development. For example, microarrays of root genes that respond to specific mineral or nutrient deficiencies could allow silviculturalists to judge whether or not a new fertilization regimen was likely improve growth rates or wood quality well before the phenotypic responses could be detected. Such new techniques will provide the means for addressing current biological constraints that limit forest productivity in the southeastern U.S.
