http://hdl.handle.net/10362/4483 Mon, 20 May 2013 06:07:49 GMT 2013-05-20T06:07:49Z http://hdl.handle.net/10362/8584 Title: Insights into the role of almond CBF transcription factors in the environmental control of cold acclimation and dormancy break Authors: Barros, Pedro Miguel Abstract: Cold is an important environmental factor that may influence plant survival and productivity. It also plays a crucial role in the seasonal development of perennial plants by regulating the extent of (winter) dormancy and that of vegetative and reproductive growth periods. This aspect is particularly relevant in fruit trees, since it may directly impact fruit production. The Prunus genus includes economically relevant species, and the almond (Prunus dulcis Mill.) stands out for its high range of genetic variability, thus being an interesting model to study specific traits of agricultural interest. Considering that low temperature signalling pathways are still poorly understood in Prunus spp., this study aimed to identify and elucidate, in almonds, the function of members of the C-repeat Binding Factor (CBF) family of transcription factors (TFs) which are known to be relevant in the response to cold. Therefore, two CBF genes (PrdCBF1 and - 2) and their corresponding regulatory regions were cloned and sequenced in this species. Southern-blot analysis and further comparisons to the recently available peach genome revealed that the almond CBF family is composed of at least five members, located in close proximity in chromosome 5. In addition, a mapping analysis suggested an association between PrdCBFs and PrdDehydrin1 (PrdDHN1, a putative CBF target gene, involved in cold acclimation) to recently reported QTLs controlling chilling requirements and blooming time. However, further analyses are necessary to confirm this association.(...) Description: Dissertation presented to obtain the Ph.D degree in Biology Thu, 01 Mar 2012 00:00:00 GMT http://hdl.handle.net/10362/8584 2012-03-01T00:00:00Z http://hdl.handle.net/10362/8560 Title: Novel transcription factors regulating the expression of the rice gene OsDREB1B Authors: Figueiredo, Duarte Dionísio Abstract: Environmental stresses are responsible for major losses in crop production worldwide. Due to an increasing world population, there is a higher demand for food, feed and fuel, which requires the development of new plant varieties with an increased yield, particularly under adverse environmental conditions. Transcription Factors (TFs) are promising candidates for plant improvement, since a single TF can modulate the expression of several genes. The AP2/ERF family of transcriptional regulators and, namely, the TFs belonging to the DREB1/CBF sub-family were described as major regulators of plant responses to abiotic stresses. Nevertheless, the transcriptional regulation of the genes coding for these TFs is still poorly understood. We focused our research on the rice gene OsDREB1B, whose gene expression had been previously described as responsive to abiotic stress, namely cold. Using semi-quantitative RT-PCR, we confirmed the cold-induction of this gene, but also observed that its response is different depending on the severity of the stress. Moreover, we observed that this gene is highly induced in response to drought stress in roots, and also in response to mechanical stress. Using the Yeast One-Hybrid system and the promoter of OsDREB1B as bait, we have screened a rice cold-induced cDNA expression library. Thereby we identified eight TFs as binding to OsDREB1B promoter: seven Zinc Finger TFs, of which three C2H2-type and four Zn Finger-Homeodomain (ZF-HD) TFs, as well as one bHLH TF, predicted as a putative Phytochrome Interacting Factor (PIF).(...) Description: Dissertation presented to obtain the Ph.D degree in Biology Sat, 01 Oct 2011 00:00:00 GMT http://hdl.handle.net/10362/8560 2011-10-01T00:00:00Z