The calcium‐dependent protein kinase ZmCDPK7 functions in heat‐stress tolerance in maize

• Published in: Journal of integrative plant biology 2021-03, Vol.63 (3), p.510-527
• Main Authors: Zhao, Yulong, Du, Hanwei, Wang, Yankai, Wang, Huali, Yang, Shaoyu, Li, Chaohai, Chen, Ning, Yang, Hao, Zhang, Yihao, Zhu, Yulin, Yang, Luyao, Hu, Xiuli
• Format: Article
• Language: English
• Subjects: ABA; Abscisic acid; Antioxidants; Calcium; Catalase; Climate change; Corn; Cytosol; Deficient mutant; Enzymatic activity; Enzyme activity; Global warming; Heat shock proteins; Heat stress; Heat tolerance; Homology; Hydrogen peroxide; Kinases; maize; Malondialdehyde; Phosphorylation; Photosynthesis; Plant stress; Pretreatment; Protein kinase; Proteins; Protoplasts; RBOHs; Respiratory burst oxidase; sHSP17.4 phosphorylation; Site-directed mutagenesis; Temperature tolerance; thermotolerance; ZmCDPK7
• ISSN: 1672-9072; 1744-7909
• DOI: 10.1111/jipb.13056

Global warming poses a serious threat to crops. Calcium‐dependent protein kinases (CDPKs)/CPKs play vital roles in plant stress responses, but their exact roles in plant thermotolerance remains elusive. Here, we explored the roles of heat‐induced ZmCDPK7 in thermotolerance in maize. ZmCDPK7‐overexpressing maize plants displayed higher thermotolerance, photosynthetic rates, and antioxidant enzyme activity but lower H2O2 and malondialdehyde (MDA) contents than wild‐type plants under heat stress. ZmCDPK7‐knockdown plants displayed the opposite patterns. ZmCDPK7 is attached to the plasma membrane but can translocate to the cytosol under heat stress. ZmCDPK7 interacts with the small heat shock protein sHSP17.4, phosphorylates sHSP17.4 at Ser‐44 and the respiratory burst oxidase homolog RBOHB at Ser‐99, and upregulates their expression. Site‐directed mutagenesis of sHSP17.4 to generate a Ser‐44‐Ala substitution reduced ZmCDPK7's enhancement of catalase activity but enhanced ZmCDPK7's suppression of MDA accumulation in heat‐stressed maize protoplasts. sHSP17.4, ZmCDPK7, and RBOHB were less strongly upregulated in response to heat stress in the abscisic acid‐deficient mutant vp5 versus the wild type. Pretreatment with an RBOH inhibitor suppressed sHSP17.4 and ZmCDPK7 expression. Therefore, abscisic acid‐induced ZmCDPK7 functions both upstream and downstream of RBOH and participates in thermotolerance in maize by mediating the phosphorylation of sHSP17.4, which might be essential for its chaperone function. Phosphorylation of the respiratory burst oxidase RBOHB and the heat shock protein‐ sHSP17.4 by ZmCDPK7 positively influences maize thermotolerance.