Identification and Expression Analysis of Heat Shock Proteins in Wheat Infected with Powdery Mildew and Stripe Rust

Heat shock proteins (HSPs), which are encoded by conserved gene families in plants, are crucial for development and responses to diverse stresses. However, the wheat (Triticum aestivum) HSPs have not been systematically classified, especially those involved in protecting plants from disease. Here, we classified 119 DnaJ (Hsp40) proteins (TaDnaJs; encoded by 313 genes) and 41 Hsp70 proteins (TaHsp70s; encoded by 95 genes) into six and four groups, respectively, via a phylogenetic analysis. An examination of protein structures and a multiple sequence alignment revealed diversity in the TaDnaJ structural organization, but a highly conserved J-domain, which was usually characterized by an HPD motif followed by DRD or DED motifs. The expression profiles of these HSP-encoding homologous genes varied in response to Blumeria graminis f. sp. tritici and Puccinia striiformis f. sp. tritici. A quantitative real-time PCR analysis indicated a lack of similarity in the expression of DnaJ70b, Hsp70-30b, and Hsp90-4b in wheat infected by B. graminis f. sp. tritici, although the expression levels of these genes were abnormal in the infected resistant and susceptible lines. Furthermore, a direct interaction between DnaJ70 and TaHsp70-30 was not detected in a yeast two-hybrid assay. This study revealed the structure and expression profiles of the HSP-encoding genes in wheat. The resulting data may be useful for future functional analyses and for further elucidating the roles of wheat HSPs during responses to fungal infections.