Calcium-dependent activation of CPK12 facilitates its cytoplasm-to-nucleus translocation to potentiate plant hypoxia sensing by phosphorylating ERF-VII transcription factors

• Published in: Molecular plant 2023-06, Vol.16 (6), p.979-998
• Main Authors: Fan, Biao, Liao, Ke, Wang, Lin-Na, Shi, Li-Li, Zhang, Yi, Xu, Ling-Jing, Zhou, Ying, Li, Jian-Feng, Chen, Yue-Qin, Chen, Qin-Fang, Xiao, Shi
• Format: Article
• Language: English
• Subjects: 14-3-3 proteins; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Calcium - metabolism; Cell Nucleus - metabolism; CPK12; cytoplasm-to-nucleus translocation; ERF-VII transcription factors; Gene Expression Regulation, Plant; Hypoxia; hypoxia sensing; phosphatidic acid; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 1674-2052; 1752-9867
• DOI: 10.1016/j.molp.2023.04.002

Calcium-dependent protein kinases (CDPKs/CPKs) are key regulators of plant stress signaling that translate calcium signals into cellular responses by phosphorylating diverse substrate proteins. However, the molecular mechanism by which plant cells relay calcium signals in response to hypoxia remains elusive. Here, we show that one member of the CDPK family in Arabidopsis thaliana, CPK12, is rapidly activated during hypoxia through calcium-dependent phosphorylation of its Ser-186 residue. Phosphorylated CPK12 shuttles from the cytoplasm to the nucleus, where it interacts with and phosphorylates the group VII ethylene-responsive transcription factors (ERF-VII) that are core regulators of plant hypoxia sensing, to enhance their stabilities. Consistently, CPK12 knockdown lines show attenuated tolerance of hypoxia, whereas transgenic plants overexpressing CPK12 display improved hypoxia tolerance. Nonethelss, loss of function of five ERF-VII proteins in an erf-vii pentuple mutant could partially suppress the enhanced hypoxia-tolerance phenotype of CPK12-overexpressing lines. Moreover, we also discovered that phosphatidic acid and 14-3-3κ protein serve as positive and negative modulators of the CPK12 cytoplasm-to-nucleus translocation, respectively. Taken together, these findings uncover a CPK12-ERF-VII regulatory module that is key to transducing calcium signals from the cytoplasm into the nucleus to potentiate hypoxia sensing in plants. The molecular mechanism by which plant cells relay calcium signals in response to hypoxia remains elusive. This study reveals that hypoxia stress rapidly stimulates Arabidopsis CPK12 and promotes its relocation from the cytoplasm to the nucleus, where it interacts with and phosphorylates ERF-VII transcription factors. The cytoplasm-to-nucleus translocation of CPK12 represents a novel mechanism to convey Ca2+ signals for fine-tuning ERF-VII-mediated hypoxia sensing in plants.