Metformin blocks BIK1-mediated CPK28 phosphorylation and enhances plant immunity

Authors: BAO, YAZHOU - Nanjing Agricultural University; ZHANG, QIAN - China Agricultural University; ZHU, HAI - Nanjing Agricultural University; PEI, YONG - Nanjing Agricultural University; ZHAO, YANING - Nanjing Agricultural University; LI, YIXIN - China Agricultural University; JI, PEIYUN - Nanjing Agricultural University; DU, DANDAN - China Agriculture University; Peng, Hao; XU, GUANGYUAN - China Agriculture University; WANG, XIAODAN - China Agricultural University; YIN, ZHIYUAN - Nanjing Agricultural University; AI, GAN - Nanjing Agricultural University; LIANG, XIANGXIU - South China Agricultural Univerisity; DOU, DAOLONG - Nanjing University

Submitted to: Journal of Advanced Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2024
Publication Date: 3/3/2024
Citation: Bao, Y., Zhang, Q., Zhu, H., Pei, Y., Zhao, Y., Li, Y., Ji, P., Du, D., Peng, H., Xu, G., Wang, X., Yin, Z., Ai, G., Liang, X., Dou, D. 2024. Metformin blocks BIK1-mediated CPK28 phosphorylation and enhances plant immunity. Journal of Advanced Research. https://doi.org/10.1016/j.jare.2024.02.025.
DOI: https://doi.org/10.1016/j.jare.2024.02.025

Interpretive Summary: Plant-derived metformin (1,1-dimethylbiguanide, MET) is a widely used first-line therapy for the type 2 diabetes for centuries. Numerous studies have shown that MET is a beneficial chemical to human health. However, how MET regulates cell functions in plant and mammalian cells is not clear. Using the model plant Arabidopsis thaliana, we found that MET can enhance plant disease resistance by increasing the production of reactive oxygens, activating protein kinase functions, and up-regulating the expression of downstream defense genes. Furthermore, MET could also enhance disease resistance in important horticultural crops including tomato, pepper, and soybean. This research revealed that MET can induce broad-spectrum immunity in multiple crop plants. The underlying molecular mechanisms we disclosed in this research will be useful for inferring MET functions in human cells, and explaining why it is effective for type 2 diabetes treatment.

Technical Abstract: Introduction: Metformin (MET), derived from the plant Galega officinalis, has been a primary therapy for type 2 diabetes (T2D) for a century. Despite its known benefits in mammalian cellular processes, its functions and underlying mechanisms remain elusive in plants. Objectives: This study determined the role of MET in inducing plant immunity and investigated the underlying mechanisms. Methods: Defense genes expression, reactive oxygen species (ROS) accumulation,mitogen-activated protein kinases (MAPKs phosphorylation, and pathogen infection assays were examined to the role of MET in enhancing plant immune response. Surface plasmon resonance (SPR) and microscale thermophoresis (MST) techniques were employed to identify MET targets in plants. Luciferase complementation assay and Co-immunoprecipitation were utilized to analyze the protein interactions. Results: Here, MET was found to enhance plant disease resistance in Arabidopsis, tomato, pepper, and soybean by activating MAPKs, inducing defense genes expression, and strengthening ROS burst. CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28), a negative regulator of immunity, was identified as a target of MET. MET inhibited the interaction between BOTRYTIS-INDUCED KINASE 1 (BIK1) and CPK28, blocking CPK28 threonine 76 (T76) transphosphorylation by BIK1 and relieving the negative regulation of immune responses by CPK28 Conclusion: Collectively, these data suggest that MET enhances plant immunity by blocking BIK1-mediated CPK28 phosphorylation.