Expression and regulation of a cold-responsive gene,CsCBFinCitrus sinensis(L.) Osbeck under low temperature, high salinity and abscisic acid

Abstract

CBF (C-Repeat/Dehydration-Responsive Element Binding Factor) as a transcription factor plays important roles in stress responses and stress-related regulatory network in plants. CsCBF, a CBF encoding gene in sweet orange (Citrus sinensis (L.) Osbeck) was isolated and investigated in expression profiles under abiotic stresses. Semi-quantitative RT-PCR analysis indicated that CsCBF expression was altered obviously in response to low temperature (4°C), high salinity (250 mM NaCl) and abscisic acid (100 μM ABA). To learn more information about CsCBF gene, genomic DNA and upstream regulatory sequence were sequenced definitely and analyzed with a series of bioinformatic tools. The results showed that there were no introns in CsCBF genomic DNA, and CBF signature sequences and AP2 DNA binding domain were also highly conserved in CsCBF amino acid sequence. In addition, more than one CBF protein was encoded in sweet orange genome. Promoter prediction analysis suggested that several stress-related cis-acting elements were detected in CsCBF regulatory region, such as MYB, MYC, ABRE, Circadian, et al.. Importantly, two putative induction regions of CBF expression, ICEr1 and ICEr2, were also found in an 85-bp section of CsCBF promoter, which may contribute to understanding of CBF transcriptional activation under stress.