Potential synergistic regulation of hsp70 and antioxidant enzyme genes in Pyropia yezoensis under high temperature stress

High temperatures have been regarded as one of the main factors limiting Pyropia yezoensis cultivation in recent years. Both the heat shock proteins and antioxidant enzymes genes were activated timely before heat damage to the cell. Here, the activities of different antioxidant enzymes under different conditions, including HSF inhibitor, CaM inhibitor, and HSP70 protein inhibitor were determined. Then, RNA-seq was performed using samples that had been pretreated with corresponding chemicals under high temperature conditions. The principal component analysis inferred that the shift of gene transcription patterns under high temperature conditions was closely related to HSF since the addition of QR suppressed the changes in gene transcription pattern. The hsp70 genes and antioxidant enzyme genes were categorized into three groups by the method of WGCNA. And the HSE sites were identified using plantPAN and FIMO in most genes of the categories showed relationship to HSF. Quantitative RT-PCR analysis of designated genes (FMPK >10) indicated that the expression of hsp70 and antioxidant enzyme genes in Py. yezoensis showed various transcriptional patterns, including upregulation, downregulation, and no significant changes in response to high temperature stress. The classification between qRT-PCR and WGCNA results showed a certain consistency. Considered the results above together, it was speculated that there were different HSFs regulated the expression of different genes of hsp70 and antioxidant enzymes, and HSP70 might also regulate the expression of anti-oxidase genes under the conditions of long-term stress. Additionally, transcription factors other than HSF might be involved in the high temperature stress response. The results indicated the complexity of heat stress response mechanisms in Py. yezoensis.