Hebei Key Laboratory of Molecular and Cellular Biology, Hebei, P.R. China.
Key Laboratory of Molecular and Cellular Biology of Ministry of Education, College of Life Science, Hebei Normal University, Hebei, P.R. China.
J Exp Bot. 2018 Oct 12;69(21):5241-5253. doi: 10.1093/jxb/ery278.
Calmodulin (CaM), a multifunctional Ca2+ sensor, mediates multiple reactions involved in regulation of plant growth and responses to environmental stress. In this study, we found that AtCaM4 plays a negative role in freezing tolerance in Arabidopsis. The deletion of AtCaM4 resulted in enhanced freezing tolerance in cam4 mutant plants. Although AtCaM4 and AtCaM1 were cold-induced isoforms, cam4/cam1Ri double-mutant and cam4 single-mutant plants exhibited similar improvements in freezing tolerance, indicating that AtCaM4 plays major role. Furthermore, we found that AtCaM4 may influence freezing tolerance in a C-repeat binding factor (CBF)-independent manner as cold-induced expression patterns of CBFs did not change in the cam4/cam1Ri mutant. In addition, among the cold-responsive (COR) genes detected, KIN1, COR15b, and COR8.6 exhibited clearly enhanced expression over the long term in cam4/cam1Ri mutant plants exposed to cold stress. Using immunoprecipitation and mass spectrometry, we identified multiple candidate AtCaM4-interacting proteins. Co-immunoprecipitation assays confirmed the interaction of AtCaM4 with PATL1 in vivo and a phenotype analysis showed that patl1 mutant plants exhibited enhanced freezing tolerance. Thus, we conclude that AtCaM4 negatively regulates freezing tolerance in Arabidopsis by interacting with the novel CaM-binding protein PATL1.
钙调素（CaM）是一种多功能的 Ca2+ 传感器，介导植物生长调控和环境胁迫响应的多种反应。在这项研究中，我们发现 AtCaM4 在拟南芥的抗冻性中起负调控作用。AtCaM4 的缺失导致 cam4 突变体植物的抗冻性增强。尽管 AtCaM4 和 AtCaM1 是冷诱导的同工型，但 cam4/cam1Ri 双突变体和 cam4 单突变体植物在抗冻性方面表现出相似的改善，表明 AtCaM4 起主要作用。此外，我们发现 AtCaM4 可能以 CBF 非依赖的方式影响抗冻性，因为 CBFs 的冷诱导表达模式在 cam4/cam1Ri 突变体中没有改变。此外，在检测到的冷响应（COR）基因中，KIN1、COR15b 和 COR8.6 在长期暴露于冷胁迫的 cam4/cam1Ri 突变体植物中表现出明显增强的表达。通过免疫沉淀和质谱分析，我们鉴定了多个候选的 AtCaM4 互作蛋白。共免疫沉淀实验证实了 AtCaM4 与 PATL1 在体内的相互作用，表型分析显示 patl1 突变体植物表现出增强的抗冻性。因此，我们得出结论，AtCaM4 通过与新型 CaM 结合蛋白 PATL1 相互作用，负调控拟南芥的抗冻性。
