Molecular cloning and characterization of a novel salt-specific responsive WRKY transcription factor gene IlWRKY2 from the halophyte Iris lactea var. chinensis.

Iris lactea var. chinensis is a perennial herbaceous halophyte with high salt tolerance and ornamental value. Previous RNA sequencing analysis revealed a transcription factor gene IlWRKY2 expression was upregulated by salt stress. To obtain the full-length sequence, the basic characteristics of IlWRKY2 and its expression pattern under salt stress. Full-length cDNA of IlWRKY2 was cloned by 3'/5' RACE based on the intermediate sequence obtained by RNA sequencing analysis. Structure analysis of IlWRKY2 were performed by Compute pI/MW tool, PSIPRED and SWISS-MODEL analysis. Sequence analysis of IlWRKY2 were performed by BLAST program, DNAman software, MEGA software and MEME program. IlWRKY2 expression pattern was analyzed by quantitative real-time polymerase chain reaction. The open reading frame of IlWRKY2 is 1338 bp in length, which encodes a protein of 446 amino acids. Amino acid sequence analysis revealed that the IlWRKY2 contains one WRKY domains with a zinc finger motif C-X5-C-X23-H-X-H. Phylogenetic analysis showed that the IlWRKY2 was much closer to EgWRKY41 from Elaeis guineensis and MaWRKY42 from Musa acuminata subsp. malaccensis. Furthermore, the expression of IlWRKY2 in I. lactea var. chinensis shoots was upregulated by different concentrations of NaCl treatment and increased 16-fold after treatment with 200 mM NaCl for 12 h. Obtained the full-length cDNA of IlWRKY2 which belongs to Group II-b WRKY subfamily. IlWRKY2 expression was obviously induced by salt stress in I. lactea var. chinensis shoots and it may play an important role in halophyte I. lactea var. chinensis adaptation to environmental salt stress.