Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2004
Publication Date: 3/1/2005
Citation: Lippert, D., Zhuang, J., Ralph, S., Ellis, D.E., Gilbert, M., Olafson, R., Ritland, K., Ellis, B., Douglas, C., Bohlmann, J. 2005. Proteome analysis of early somatic embryogenesis in picea glauca. Molecular and Cellular Proteomics. 5:461-473. Interpretive Summary: We know very little about the molecular and biochemical events which occur during embryo formation and maturation in forest trees. Spruce is a good model for studying embryo formation due to the existence of a well characterized system, known as somatic embryogenesis, where large numbers of genetically identical embryos can be obtained. This permits the sampling of discrete stages during embryo development to analyze changes occurring during embryo formation. This study has looked at the differential expressions levels of individual proteins in four developmental stages during embryo formation to aid in our understanding of what proteins are typically involved in the process of embryo maturation. Forty-nine proteins were identified to vary significantly during this process. These proteins were partially sequenced and their putative identity and functions deduced from published gene sequences. This work provides a base line for basic studies in conifer embryogenesis as well as tools to monitor somatic embryo formation in the commercial production of uniform elite conifer propagules for the forestry industry.
Technical Abstract: Forests are is a valuable natural resource for many countries. Rapid production of large quantities of genetically improved and uniform tree seedlings for restocking harvested lands is a key component of sustainable forest management programs. Vegetative propagation through somatic embryogenesis has the potential to meet this need in conifers and can offer the added benefit of ensuring consistent seedling quality. Although in commercial production, conifer mass production through somatic embryogenesis is relatively new and there are numerous biological unknowns regarding this complex developmental pathway. To aid in unravelling the embryo developmental process, two-dimensional electrophoresis was employed to quantitatively assess the expression level of proteins across four stages of somatic embryo maturation in white spruce (0, 7, 21 and 35 days post ABA treatment). Forty-nine differentially expressed proteins have been identified representing those that display a significant change in abundance and which can be detected as early as day 7 of embryo development. These proteins are involved in a variety of cellular processes, many of which have not previously been associated with embryo development. The completion of this study was greatly assisted by the availability of a substantial EST resource developed for white, sitka and interior spruce. The combined use of these spruce expressed sequence tags (ESTs) in conjunction with Genbank accessions for other plants improved the rate of protein identification from 38% to 62% when compared with Genbank alone using automated, high-throughput techniques. This underscores the utility of EST resources in a proteomic study of any species for which a genome sequence is unavailable.