Differential Expression Pattern of Heat Shock Protein Genes in Toxigenic and Atoxigenic Isolate of Aspergillus flavus
Raman Thakur
Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan-173234, Himachal Pradesh, India.
Shraddha Tiwari
Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan-173234, Himachal Pradesh, India.
Jata Shankar *
Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat, Solan-173234, Himachal Pradesh, India.
*Author to whom correspondence should be addressed.
Abstract
Aflatoxin biosynthesis in Aspergillus flavus requires coordinated expression of regulatory and structural genes. Aflatoxin production is optimum at 24-30°C and inhibition occurs at temperature higher than 35°C. Chaperones or heat-sock proteins are involved in processing of cellular protein and heat-stress induced protein, hence, we studied the genes encoding for heat-shock proteins under the influence of temperature (30°C vs. 37°C). A. flavus isolates, aflatoxigenic (MTCC9367) and atoxigenic (MTCC11580) were grown in glucose minimal salt broth for 24 hours for expression profile of selected genes using quantitative real-time PCR. We monitored the expression profile of genes encoding for heat-shock proteins (hsp98, hsp90, hsp70 and hsp60) and regulatory gene of aflatoxin biosynthesis pathway aflR. We found the similar trend for heat-shock proteins gene expression except hsp70 in aflatoxigenic and atoxigenic isolates of A. flavus. Expression for hsp70 was found to be upregulated at 30°C (vs 37°C)in atoxigenic isolate (P<0.001) of A. flavus in comparison of toxigenic (P<0.05) isolate. Since, heat-shock proteins are involved in protein folding and conformational stability of cellular proteins to maintain the biological activity, our data on transcripts encoding for heat-shock proteins suggested it may influence the aflatoxin biosynthesis process in A. flavus.
Keywords: Aflatoxin, Aspergillus flavus, heat-shock protein, hsp90, hsp70, Aspergillus parasiticus