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

Abstract

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.

Genome-Wide Analysis of HSP70s in Hexaploid Wheat: Tandem Duplication, Heat Response, and Regulation

“…Furthermore, in 14 triads, at least one homeolog showed different exon/intron structures in each triad. These results were quite different from the conserved gene structures and protein motifs of TaHSP90 triads [35].…”

“…Furthermore, in 14 triads, at least one homeolog showed different exon/intron structures in each triad. These results were quite different from the conserved gene structures and protein motifs of TaHSP90 triads [35]. However, the protein motifs of more than two-thirds of the TaHSP70 triads (13 out of 18) were highly conserved.…”

“…This proportion was much higher than that for all genes at a whole-genome level (35.8%) [ 26 ]. A high proportion of gene triads was also found in TaHSP90s (100% of 18 genes) [ 35 ]. The high percentage of gene triad retention, particularly the key molecular chaperons, may be due to their important roles in plant growth and stress response.…”

Layers of crosstalk between circadian regulation and environmental signalling in plants

“…Alternative splicing also underlies transcriptomic responses to ambient temperature. For example, in hexaploid wheat (Triticum aestivum) there are alternatively spliced forms of the heat shock transcript TaHSP90 that have unique splicing patterns underlying physiological responses to warmer temperatures 72 .…”

Alternative Splicing of TaGS3 Differentially Regulates Grain Weight and Size in Bread Wheat

“…Some reports have illustrated that AS events in wheat are substantially related to grain biochemical traits such as phytoene synthase activity [ 19 ], polyphenol oxidase activity [ 25 ], and starch synthase activity [ 26 ]. AS is also involved in disease resistance [ 27 ] and abiotic stresses tolerance [ 28 , 29 , 30 ]. Studies related to AS on wheat grain traits are mainly focused on grain quality.…”