In silico mining of WRKY TFs through Solanum melongena L. and Solanum incanum L. transcriptomes and identification of SiWRKY53 as a source of resistance to bacterial wilt

Abstract

Eggplant growth and yield is highly disrupted due to attack by microbial pathogens including bacteria, viruses and fungi. Among these, Ralstonia solanacearum, a soil-borne gram negative bacterium threatens the eggplant productivity on large-scale. While its management is difficult, it could be controlled if the wild species offering candidate resistant genes are known. Since WRKY transcription factors (TFs) are among the major class of regulatory genes playing crucial roles in plant survival during stress conditions challenged due to heat, cold, drought, salinity and pathogens, we utilized the de novo transcriptome sequence of Solanum melongena and S. incanum (available at the TSA database of NCBI with primary accessions GAYR00000000 and GAYS00000000) for mining and characterization of WRKY TFs. As per our findings, 32 and 34 putative WRKY TFs in S. melongena and S. incanum, respectively were identified, which were annotated as WRKY 1 to WRKY 75, and were classified into groups I, IIA-IIE, and III following the fundamental classification of WRKY TFs in eukaryotes. Phylogenetic analysis of all the SmWRKY and SiWRKY showed significant correlation with this classification system. Further, quantitative RT-PCR expression profiling of selected WRKY genes was carried out at different time intervals in eggplant infected by R. solanacearum cultures. Expression analysis revealed the drastic up-regulation of group III SiWRKY53 during 7th day (12.6 folds) and 10th day (27.1 folds) of infection, confirming it as an ideal target gene for enhanced tolerance to bacterial wilt and molecular breeding for development of resistant eggplant cultivars.