PUB40 attenuates Phytophthora capsica resistance by destabilizing the MEK2-SIPK/WIPK cascade in Nicotiana benthamiana

Authors: ZHANG, YIFAN - China Agricultural University; WANG, JINGHAO - China Agricultural University; PI, LEI - China Agricultural University; WANG, NAN - Jiangsu Academy Agricultural Sciences; Peng, Hao; YIN, ZHIYUAN - Nanjing Agricultural University; DOU, DAOLONG - Nanjing Agricultural University

Submitted to: Phytopathology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2024
Publication Date: 6/27/2024
Citation: Zhang, Y., Wang, J., Pi, L., Wang, N., Peng, H., Yin, Z., Dou, D. 2024. PUB40 attenuates Phytophthora capsica resistance by destabilizing the MEK2-SIPK/WIPK cascade in Nicotiana benthamiana. Phytopathology Research. 6. Article 31. https://doi.org/10.1186/s42483-024-00249-6.
DOI: https://doi.org/10.1186/s42483-024-00249-6

Interpretive Summary: Plants use biochemical signaling pathways to activate and regulate production of defense compounds that improve resistance to diseases. The MEK2-SIPK/WIPK signaling pathway is known to be regulated by one or more enzymes in a group of E3 ubiquitin ligases, but which E3 ligases degrade the proteins in this signaling pathway remain unknown. In this study, plant PUB-family E3 ligases were screened and characterized for involvement in plant resistance to the pathogen Phytophthora capsici. Disruption of a candidate E3 ligas known as NbPUB40 significantly enhanced plant resistance to P. capsici. These results revealed for the first time that the NbPUB40 protein regulates plant resistance to Phytophthora by destabilizing the MEK2-SIPK/WIPK signaling pathway. This information increases understanding of plant immune responses to pathogen infection and provide potential targets for plant cultivar development towards effective resistance to diseases.

Technical Abstract: The mitogen-activated protein kinase (MAPK) cascade MEK2-SIPK/WIPK is essential for immunity in Solanaceae plants. This cascade is tightly controlled to prevent harmful hyperactivation. However, the E3 ubiquitin ligases utilized by plants to reduce MEK2- SIPK/WIPK protein levels remain largely elusive. Here, we confirmed the essential role of Nicotiana benthamiana MEK2-SIPK/WIPK in resistance to the oomycete pathogen Phytophthora capsici. Using tobacco rattle virus (TRV)-based gene silencing, we screened prevalent plant U-box protein (PUB)-type E3 ligases with Armadillo (ARM) repeats to characterize those involved in Phytophthora resistance and MEK2-SIPK/WIPK degradation. We found that pub40 knockdown mutants exhibited significantly enhanced resistance to P. capsici. NbPUB40 was under ubiquitination and proteasomal degradation in planta, with two conserved sites (Cys28 and Val41) in the U-box domain being essential for its activity. NbPUB40 was shown to interact with the whole MEK2-SIPK/WIPK cascade and promote their degradation, the ubiquitination levels of which were also notably reduced in the pub40 mutant. Our results reveal a mechanism in which a PUB E3 ubiquitin ligase negatively regulates plant P. capsici resistance by destabilizing the MEK2-SIPK/WIPK cascade.