Transcript profiling: A tool to assess the development of conifer embryos

Embryogenesis is a phase of development that has been understudied at the m olecular level, especially in conifers. Somatic embryogenesis, the asexual propagation of embryos, provides insights into development and has major ap plications in the forestry industry. Loblolly pine is the most important co mmercial species in the United States; however, it is recalcitrant to somat ic embryogenesis methods. An appreciation of gene expression and the develo pment of 'expression markers' would allow us to follow conifer embryogenesi s more closely and to gain some insight into the metabolic states of zygoti c and somatic embryos. We have employed the techniques of differential disp lay to identify genes whose mRNA abundance changes over the course of devel opment. We have isolated around 500 cDNAs and propose the establishment of a database of transcript levels in somatic and zygotic pine embryos over th e course of development using cDNA arrays. Approximately one-third of our c DNAs have similarity to sequences in the Genbank. Our intention is to gain insight into cell physiology and biochemistry by identifying inducible tran scripts. This information will form the basis of testable hypotheses regard ing manipulation of embryo development in tissue culture. Experiments deriv ing from transcript profiling will provide insight into development. The 'e xpression markers' will allow a classification system more closely tied to metabolic state and the integration of these data into ongoing physiologica l research will lead to improved protocols for somatic embryogenesis.