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

Embryogenesis is a phase of development that has been understudied at the molecular level, especially in conifers. Somatic embryogenesis, the asexual propagation of embryos, provides insights into development and has major applications in the forestry industry. Loblolly pine is the most important commercial species in the United States; however, it is recalcitrant to somatic embryogenesis methods. An appreciation of gene expression and the development of ‘expression markers’ would allow us to follow conifer embryogenesis more closely and to gain some insight into the metabolic states of zygotic and somatic embryos. We have employed the techniques of differential display to identify genes whose mRNA abundance changes over the course of development. We have isolated around 500 cDNAs and propose the establishment of a database of transcript levels in somatic and zygotic pine embryos over the course of development using cDNA arrays. Approximately one-third of our cDNAs have similarity to sequences in the Genbank. Our intention is to gain insight into cell physiology and biochemistry by identifying inducible transcripts. This information will form the basis of testable hypotheses regarding manipulation of embryo development in tissue culture. Experiments deriving from transcript profiling will provide insight into development. The expression markers' will allow a classification system more closely tied to metabolic state and the integration of these data into ongoing physiological research will lead to improved protocols for somatic embryogenesis.