Functional expression of MAP kinase TiHOG1 gene in Tilletia indica inciting Karnal bunt of wheat

Abstract

Tilletia indica is an important quarantined fungal pathogen inciting Karnal bunt disease of wheat. In fungal pathogens, the Hog1-type MAPK is involved in response to various stresses and virulence. In the present study,we identified, characterized and analyzed functional expression of the TiHog1-type gene. As HOG1 homologous genes are salt-inducible, the TiHOG1 gene (1104 bp) was amplified in 1 M NaCl stressed condition in T. indica; cloned in pJET2.0 cloning vector. The TiHOG1 gene was subcloned in expression vector (pRS426Gpd plasmid) and sequences were analyzed. The TiHOG1 in pRS426GPD (pRS426GPD-TiHOG1) was expressed functionally in heterologous system (Saccaromyces cerevisiae). TiHOG1 protein exhibits high amino acid similarity with the homologous protein sequences in Tilletia caries, Ustilago maydis and Puccinia graminis f. sp. tritici. Functional expression of TiHOG1 in S. cerevisiae ∆hog1 mutant showed that TiHOG1 was restored salinity stress tolerance up to 1 M NaCl, 1 M KCl, 0.25 CsCl2, 0.5 M MgCl2 and 0.5 M CaCl2 and osmostress tolerance up to 1 M sorbitol and 1 M sucrose. The expression of TiHOG1 was elicited up to 19.81-fold in response to a susceptible host, whereas resistant host factors showed 9.65-fold transcripts. This first study revealed involvement of a TiHOG1 gene in stress tolerance and may have a role in pathogenesis of T. indica (Karnal bunt of wheat).