Isolation and expression of a cold-responsive gene PtCBF in Poncirus trifoliata and isolation of citrus CBF promoters
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C-repeat/dehydration-responsive element binding factor (CBF) plays important roles in cold response network in plants. Here, one member of CBF coding gene family in trifoliate orange (Poncirus trifoliata), designated as PtCBF, was isolated. Semi-quantitative reverse transcription-polymerase chain reactions showed up-regulation of PtCBF not only under low temperature but also induced by abscisic acid. Additionally, the CBF genomic fragments in four citrus species including trifoliate orange, sweet orange (Citrus sinensis), pummel (Citrus grandis) and rough lemon (Citrus jambhiri) were isolated with complete open reading frames. According to the results of alignment analysis between full length cDNA and genomic DNA sequences in trifoliate orange, there were no introns in PtCBF. Moreover, the results of multiple sequence alignment analysis and phylogenetic analysis on putative protein sequences suggested that the AP2 DNA binding domains and CBF signature sequences were highly conserved in four citrus CBF proteins. Finally, the CBF promoters in above citrus species were isolated, which provides some information concerning promoter function.
Additional key wordsabscisic acid Citrus grandis Citrus jambhiri Citrus sinensis low temperature trifoliate orange
C-repeat/dehydration-responsive element binding factor
semi-quantitative reverse transcription-polymerase chain reaction
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