Furthermore, shoot explants taken from somatic embryo-derived white spruce trees as old as 10 years were shown to be responsive to SE induction. It has also been postulated that exposure to PGR in culture increases DNA methylation levels, which in turn may stimulate cell division and differentiation leading to Lumiracoxib increased propensity for organogenesis or SE induction. Thus, in addition to testing the ability of 2,4-Dand 6-benzyladenine to promote SE induction, as has been reported for zygotic embryos of radiata pine and for shoot explants of white spruce, it was of interest to test whether other auxins would be successful in promoting SE induction. Although this approach failed to generate embryonal masses, six call us lines were selected for analysis: two derived from shoot buds of somatic embryo-derived trees and four derived from axillary shoots generated invitro from shoots collected from four seed-derived trees. The second objective was to target transcriptional factors whose expression is reflective of tissue identity, with the specific intent to assess the developmental ��character�� of the induced tissues. Genes linked to cellular metabolism were also analyzed, in part to assess the impact of different PGR compositions within the induction media. In order to provide a foundation upon which to compare the primordial and axillary shoot-derived tissues, three EM lines induced from immature zygotic embryos were also analyzed, which further provides an opportunity to describe each of the five functional categories of genes selected for the analyses. Historically, analysis of genes with a high level of expression stability have played a central role in gene expression profiling. While the selection and application of reference gene scan be complex, reference gene analysis was used in this study to first evaluate the technical variance associated with RNA and cDNA Hemicholinium Bromide preparation, and then to assess the level of biological variability, with the primary goal of establishing a foundation from which to interpret differences in gene expression. Based on an extensive survey of reference genes conducted during a study of white spruce SE induction from primordial shoots of white spruce, YLS8 was selected as a potentially effective reference gene for radiata pine.