Genome Wide Identification of Target Heat Shock Protein90 Genes and Their Differential Expression against Heat Stress in Wheat

Aims: To study the genetic and transcript profiling of the genes specifying cytosolic HSP90s in Triticum aestivum.
Study Design: Random sampling.
Place and Duration of Study: Indian Agricultural Research Institute, New Delhi, India, between August to December, 2011.
Methodology: We include C-306 (thermotolerant) and PBW343 (thermosusceptible) cultivars of wheat for the study. Total RNA was isolated using Trizol method and gene was identified and isolated using RT-PCR. In silico characterization was done using different bioinformatic tools. Quantitative real time PCR was carried out using BioRad CFX96 platform and Pfaffl’s method was used for the comparative change in fold expression of the gene.
Results: Here, we report cloning of an HSP90 gene from C-306 wheat cultivar having an ORF of 700 amino acids. Genome Blast identified 3 different clusters of reference sequence on chromosome no 4, 8 and 9 having LOC 100125696 and showing maximum homology with HSP90 reported from Triticum aestivum. Pure amino acid composition revealed highest composition of glutamic acid followed by lysine and leucine whereas, cysteine composition was lowest. Protein characterization showed the existence of 10 networks of coevolved amino acids. Quantitative real time PCR showed 1.5, 4.5, 5 & 7.4 fold increase in expression of HSP90 in case of C-306 compared to 2.5, 6.4, 6.9 & 5.6 fold increase in case of PBW343 at vegetative (root & shoot), pollination and milky dough stage. Multiple co-chaperones of HSP90 were observed by immunoblot assay in response to differential heat shock.
Conclusion: This investigation proves that HSP90 is one of the key components of defense mechanism in wheat against heat stress which requires the formation of co-chaperone complexes with HSP70 for its functional activity. There is a need to exploit the transcription factors associated with HSP90 and its regulation and differential expression in order to use it for developing thermotolerant wheat cultivars.