Oat seed storage protein genes: Promoter studies in transgenic tobacco plants.
|Title:||Oat seed storage protein genes: Promoter studies in transgenic tobacco plants.|
|Abstract:||The seed storage proteins of oat are mainly represented by the globulins (75%) and the prolamins (10%). These proteins are only found in the endosperm and accumulate within protein bodies during the maturation of the oat seeds. Three genomic sequences encoding globulin polypeptides and one avenin genomic sequence encoding an oat prolamin (avenin) have been isolated and characterized. The respective promoters of these genomic clones were fused to the coding sequence of the $\beta$-glucuronidase reporter gene (GUS). These constructs, together with the entire sequence of a globulin gene, were transferred into tobacco via Agrobacterium tumefaciens. Analysis of the transgenic tobacco seeds showed for the first time that the promoters of the oat globulin and avenin genes are able to regulate the expression of the GUS sequence in an endosperm-specific and developmentally controlled manner in a dicot plant, as in oat seeds with the original seed storage protein gene. One of the globulin promoters was shown to be probably inactive, whereas two other promoters appear to direct strong expression in the seeds of transgenic tobacco plants. A deletion analysis on one of the functional promoters demonstrated that a portion of the promoter upstream of nucleotide -259 (relative to the start of transcription as determined in oat) was required for expression. Sequence analysis of the globulin promoters showed the lack of conserved elements which are found in other storage protein gene promoters, and believed to play an important role in the regulation of seed storage protein genes. It was nonetheless demonstrated in this study that the absence of such elements did not prevent a correct functionality of the oat globulin promoters in transgenic tobacco seeds. The avenin promoter, when fused to the GUS sequence, also showed strong expression in the endosperm of transgenic tobacco seeds. Sequence analysis of the upstream region of the avenin gene confirmed the presence of a highly conserved 'prolamin box'. The possible role of this element was therefore further demonstrated in this work. This work has also showed for the first time a difference in the choice of transcriptional start sites of two monocot (oat) seed storage protein genes after transfer into a dicot species (tobacco).|
|Collection||Thèses, 1910 - 2010 // Theses, 1910 - 2010|