Insights into the role of almond CBF transcription factors in the environmental control of cold acclimation and dormancy break

Dissertation presented to obtain the Ph.D degree in Biology

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.(...)

This work was supported by a PhD fellowship (Ref. SFRH/BD/31594/2006) awarded to Pedro Barros, and also through the grant # PEst- OE/EQB/LA0004/2011, both from the Fundação para a Ciência e Tecnologia (FCT).