An abiotic stress-responsive WRKY gene is transiently induced in response to cold and drought stresses in Poncirus trifoliata

Abstract A partial cDNA sequence sharing significant homology with WRKY transcription factors (TFs) was previously amplified from Poncirus trifoliata by reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers. In this study, the full-length cDNA sequence of this cDNA, PtrWRKY3, was obtained by RACE method from P. trifoliata. The length of PtrWRKY3 cDNA was 1908 bp and contained open reading frame coding for a 512-amino-acid polypeptide. The ortholog of this gene, CpWRKY3, was also cloned and sequenced from Citrus paradisi (grapefruit). The gene consists of 1550 bp cDNA encoding a protein of 516 amino acids. Both genes have double WRKY domains with Cys2His2 signature motif and showed 98% amino acid sequence identity with each other. They were tightly clustered together and showed a close phylogenetic relation with putative WRKY TFs from different woody perennial plants. The expression of the WRKY3 gene was analyzed quantitatively by northern blot and real-time RT-PCR in response t...