Alternative splicing diversifies the heat response and evolutionary strategy of conserved Heat Shock Protein 90 in bread wheat (Triticum aestivum L.)

Background Crops are challenged by the increasing high temperature. Heat shock protein 90 (HSP90), a molecular chaperone, plays a critical role in the heat response in plants. However, the comprehensive response profiles of HSP90s are largely unknown.Results Using the newly released wheat reference sequence, we identified 18 HSP90s that were highly conserved and presented as triplets. Transcriptome analysis showed that the expression and transcriptional regulation of HSP90s displayed conserved trends among the three HSP90 homologs within a triplet. Based on our previous data generated by combining full-length single-molecule sequencing and Illumina short read sequencing, 126 isoforms of HSP90 were identified and each HSP90 comprised one to three major isoforms. Intriguingly, unlike the conserved transcriptional regulation of HSP90s , different alternative splicing events were characterized among major isoforms generated by HSP90s in triplets under heat stress. Furthermore, many heat-responsive alternative events were also characterized, especially in the early heat response when transcriptional regulation had not been initiated, and the alternative splicing regulation between HSP90s in the triplets was distinctly different.Conclusions This study shows that alternative splicing diversified the heat response of the conserved HSP90 gene family and highlighted the evolutionary divergence of polyploidy wheat.