Molecular cloning and characterization of a group II WRKY transcription factor from Jatropha curcas, an important biofuel crop.

The WRKY family of transcription factors (TFs) play an intricate role in regulating the stress signaling pathways by autoregulation or may be by cross regulation through interaction with other proteins. Although WRKY TFs are considered to be plant specific, however, their presence has been reported from unicellular algae, slime mould, and gymnosperms. We have isolated the JcWRKY cDNA from an important biofuel crop Jatropha curcas growing in the wastelands of India. The JcWRKY gene has an ORF of 693 bp and encodes a 230 amino acids protein with estimated molecular mass of 25.25 kDa. JcWRKY shows close homology to FaWRKY1 and St-WRKY1. The JcWRKY contains seven potential phosphorylation sites, which might be involved in regulating its function. The transcript analysis revealed that the JcWRKY transcript gets upregulated in response to salinity, dehydration, salicylic acid (SA), methyl jasmonate (MeJa), and collar rot fungus Macrophomina. However, maximum expression is observed under SA, highlighting its role in enhancing systemic acquired resistance for disease tolerance. The JcWRKY recombinant protein showed binding to W-box of pathogenesis related-1 (PR-1) and iso1 (encoding isoamylase1) promoters. Overexpression of JcWRKY in Escherichia coli enhanced the growth of cells in NaCl, KCl, mannitol, sorbitol, SA, and MeJa treatments, indicating that it protects and promotes growth under ionic, osmotic, and chemical stresses. The enhancement in growth can be due to the regulation of stress responsive genes. Therefore, it can be used as an important gene for enhancing abiotic and biotic resistance in plants and to facilitate faster growth of E. coli cells under stress conditions for efficient expression.