Table_5_Alternative Splicing Diversified the Heat Response and Evolutionary Strategy of Conserved Heat Shock Protein 90s in Hexaploid Wheat (Triticum aestivum L.).XLSX

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 evolutionary conservation and divergence of HSP90s homeologs in polyploidy crops are largely unknown. Using the newly released hexaploid wheat reference sequence, we identified 18 TaHSP90s that are evenly distributed as homeologous genes among three wheat subgenomes, and were highly conserved in terms of sequence identity and gene structure among homeologs. Intensive time-course transcriptomes showed uniform expression and transcriptional response profiles among the three TaHSP90 homeologs. Based on the comprehensive isoforms generated by combining full-length single-molecule sequencing and Illumina short read sequencing, 126 isoforms, including 90 newly identified isoforms of TaHSP90s, were identified, and each TaHSP90 generated one to three major isoforms. Intriguingly, the numbers and the splicing modes of the major isoforms generated by three TaHSP90 homeologs were obviously different. Furthermore, the quantified expression profiles of the major isoforms generated by three TaHSP90 homeologs are also distinctly varied, exhibiting differential alternative splicing (AS) responses of homeologs. Our results showed that the AS diversified the heat response of the conserved TaHSP90s and provided a new perspective for understanding about functional conservation and divergence of homologous genes.

农作物正面临日益加剧的高温胁迫。热激蛋白90（Heat shock protein 90, HSP90）作为一类分子伴侣，在植物的热响应过程中发挥关键作用。然而，多倍体农作物中HSP90部分同源基因的进化保守性与分化机制目前尚未得到充分阐明。本研究借助最新发布的六倍体小麦参考基因组序列，共鉴定得到18个TaHSP90基因，它们作为部分同源基因均匀分布于小麦的三个亚基因组中，且各部分同源拷贝间的序列一致性与基因结构均高度保守。深入的时间序列转录组分析显示，这三个TaHSP90部分同源基因的表达模式与转录响应特征整体一致。通过整合全长单分子测序与Illumina短读长测序获得的全面转录本异构体信息，本研究共鉴定得到126种转录本异构体，其中包含90个全新的TaHSP90转录本异构体；且每个TaHSP90基因可产生1至3种主要转录本异构体。有趣的是，三个TaHSP90部分同源基因所产生的主要转录本异构体的数量与剪接模式均存在显著差异。此外，三个TaHSP90部分同源基因的主要转录本异构体的定量表达谱同样存在显著差异，表现出部分同源基因间的差异化可变剪接（Alternative Splicing, AS）响应。本研究结果表明，可变剪接使得保守的TaHSP90基因的热响应过程更具多样性，同时为解析同源基因的功能保守性与分化机制提供了全新视角。