Expression data from poplar stems

We study differences in gene expression between Populus P35S::PLGT , RNAi_PLGT and control/WT plants, affecting tropic responses and stem development. We used microarrays to detail the global program of gene expression underlying morphological and developmental changes droved by th etransgenic manipulations of PLGT gene. By screening activation tagging population we identified the PLAGIOTROPICA (PLGT) mutant. The mutant is severely impaired in gravitropic responses and displays consistent south orientation of the shoot tip in the overexpressing plants. We positioned the tag, localized a putative candidate gene and verified transcription activation. The activated gene encodes an ortholog of the OCTOPUS gene from Arabidopsis. We fully recapitulated the phenotype by overexpression of the gene into the same genotype under strong constitutive promoter (P35S::PLGT). We further downregulated the gene using RNAi approach. The gene was most highly expressed in young stems and phloem tissues. Poplar stem segments derived from the 5th internodes were selected for RNA extraction and hybridization on Affymetrix microarrays. We sought to uncover the affected geens associated with the native function of this gene by looking at the genome-wide expression changes in the overexpression, downregulated and wild type plants. To do that, we selected stem segments derived from the 5th internodes tissue, becuase the native expression of PLGT was found to be highest in this tissue.