Poster: Temperature responses
Abs #
131: Characterization of a CBF pathway for low temperature-induced gene regulation in Poncirus trifoliata (L.) Raf. and Citrus paradisi Macf.
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Presenter: |
Champ, Karen I., kichamp@mail.ifas.ufl.edu |
Authors | Champ, Karen I. (A) Febres, Vicente J. (A) Moore, Gloria A. (A) | | Affiliations: |
(A): University of Florida
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Citrus species are generally considered cold sensitive, yet Poncirus trifoliata, an interfertile Citrus relative, is extremely cold tolerant and can survive freezes at -20οC if fully cold acclimated. However, the molecular basis of this difference in cold tolerance is poorly understood. The CRT/DRE Binding Factor (CBF) pathway plays a major role in low temperature-regulated gene expression in many plants. The primary objective of this research is to investigate the presence of a CBF pathway in P. trifoliata and C. paradisi (grapefruit). We are isolating and characterizing P. trifoliata and C. paradisi cold-regulated (COR) genes and their promoters. Based on our results, P. trifoliata and C. paradisi do contain a CBF pathway for COR gene expression, and similar to other species, P. trifoliata and C. paradisi appear to contain small CBF families. Characterization of COR promoters identified the presence of motifs conserved in the promoters of COR genes of other species. Notably, the 5' sequences of four COR promoters contain elements resembling the C-repeat (CRT)/dehydration-responsive element (DRE) core. Additional motifs previously implicated in low temperature signaling were also present including ABREs, and MYB and MYC recognition sites. CBF-like cDNAs were isolated from P. trifoliata and C. paradisi. The nucleotide and amino acid sequences of PtCBF and CpCBF are highly similiar, although differences in cold-induced expression were observed. PtCBF accumulates earlier and to higher levels than CpCBF, perhaps contributing to the differences in cold tolerance. We speculate that this difference may be in the promoter regions, and we are isolating them for comparison. We are also isolating and characterizing other CBF family members.
