Comparative expression analysis of potential pathogenicity-associated genes of high- and low-virulent Sporisorium scitamineum isolates during interaction with sugarcane.

Sporisorium scitamineum is a teleomorphic, biotrophic fungus causing the globally prevalent sugarcane smut disease in sugarcane. The severity of the disease depends on two major factors, viz. degree of resistance in the host genotype and virulence level of the pathogen. Hence, in this study, temporal transcriptomic expression of potential pathogenicity-associated genes of two distinctly virulent S. scitamineum isolates, viz. SsV89101 (low virulent) and Ss97009 (high virulent) were analyzed during interaction with a smut susceptible sugarcane cv. Co 97009 at six different time intervals. The pathogenicity-associated genes profiled in this study comprises 14 plant cell wall degrading enzymes (PCWDEs) and ten candidates secreted effector protein-coding (CSEPs) genes. Absolute quantification of pathogen biomass and comparative expression profiling analyses of these pathogenicity-associated genes during host–pathogen interaction indicated that there was a significant variation between low and high virulent isolates. More precisely, the higher and early expression (24 hpi) of certain PCWDEs, viz. Chitinase-1 and Laccase, and the CSEPs, viz. SUC2, SRT1 and CMU1 during the colonization of high virulent isolate suggested that they might possibly play a major role in facilitating faster and successful pathogen ingress, and tissue colonization than the less-virulent isolate. Transcript expression profiling of Chitinase and Laccases were also in correlation with their corresponding enzyme activity assays. Comprehensively, this quantitative temporal expression analysis has provided critical insights into the early expression of pathogenicity-associated genes and their putative role in attributing to higher virulence. Moreover, this study provides valuable clues for the screening of candidate virulence determinants for further functional characterization of the test pathogen isolates used for the evaluation of smut resistance in breeding clones. [ABSTRACT FROM AUTHOR]