The formation of embryos within the seeds of pine trees differs from seed formation in traditional crop and vegetable plants. While in both cases an embryo forms inside a seed, develops and finally germinates to form a plant, the morphology, biochemistry and genetics of the processes in gymnosperms (e.g. pine) and angiosperms (e.g. carrot) are distinctly different. Embryogenesis is the result of a regulated program of gene activity and the elucidation of the program for loblolly pine is the goal of this project. The multiplication of pine embryos in a laboratory setting and the production of plantlets, has great implications for reforestation
After corn, forest products are the second most valuable US agricultural product. Loblolly pine (Pinus taeda L.) is the primary commercial species in southern conifer forests covering 13.4 million hectares, and over 1.5 billion loblolly pine seedlings are planted annually. Somatic embryogenesis, a tissue culture technique for embryo multiplication, is an excellent experimental tool for investigating embryogenesis in this tree. However, success of the technique is genotype-dependent and remains inefficient. Knowledge of the program of gene expression in natural and laboratory-cultivated embryos will provide insight into varying metabolism of these embryos and a basis for protocol improvement.
A cDNA library will be created from loblolly pine zygotic (natural) and somatic (laboratory-cultivated) embryos. Together, these will represent a combined set of transcripts expressed during all stages of embryogenesis, thus giving a 'snapshot' of genes participating in the formation of the pine embryo. Randomly selected cDNA clones will be 5' end-sequenced to generate 35,000 Expressed Sequence Tags or ESTs. These ESTs will be clustered and assembled to construct a non-redundant pine EST database (TIGR Gene Index).
The non-redundant cDNA clone set will be used to obtain gene expression profiles during various stages of zygotic and somatic loblolly pine embryogenesis. This approach should identify the genes active in embryogenesis allow determination of their identities and temporal expression patterns. A comparison of profiles from laboratory-grown and natural embryos will allow insights into embryogenesis to be gained, and further development of improved protocols for loblolly pine somatic embryogenesis. Together, these data will provide the first detailed overview of genome-wide gene expression patterns in conifer embryo development. In the long-term, this kind of information will be useful in developing strategies to accelerate clonal propagation.
