CsCIPK11-Regulated Metalloprotease CsFtsH5 Mediates the Cold Response of Tea Plants.

Photosystem II repair in chloroplasts is a critical process involved in maintaining a plant's photosynthetic activity under cold stress. FtsH (filamentation temperature-sensitive H) is an essential metalloprotease that is required for chloroplast photosystem II repair. However, the role of FtsH in tea plants and its regulatory mechanism under cold stress remains elusive. In this study, we cloned a homolog gene in tea plants, named , and found that CsFtsH5 was located in the chloroplast and cytomembrane. RT-qPCR showed that the expression of was increased with leaf maturity and was significantly induced by light and cold stress. Transient knockdown expression in tea leaves using antisense oligonucleotides resulted in hypersensitivity to cold stress, along with higher relative electrolyte leakage and lower values. To investigate the molecular mechanism underlying involvement in the cold stress, we focused on the calcineurin B-like-interacting protein kinase 11 (), which had a tissue expression pattern similar to that of and was also upregulated by light and cold stress. Yeast two-hybrid and dual luciferase (Luc) complementation assays revealed that CsFtsH5 interacted with CsCIPK11. Furthermore, the Dual-Luc assay showed that CsCIPK11-CsFtsH5 interaction might enhance CsFtsH5 stability. Altogether, our study demonstrates that is associated with and plays a positive role in maintaining the photosynthetic activity of tea plants in response to low temperatures.