The role of the MAP kinase\u2212kinase protein StMKK1 in potato immunity to different pathogens

Xiaokang Chen,Wenbin Wang,Pingping Cai,Yu Du,Ziwei Wang,Tingting Li

doi:10.1038/s41438-021-00556-5

Abstract

Mitogen-activated protein kinase (MAPK) cascades play important roles in plant immunity. Previously, we reported that the potato StMKK1 protein negatively regulates Nicotiana benthamiana resistance to Phytophthora infestans. However, the functions of StMKK1 in potato immunity are unknown. To investigate the roles of StMKK1 in potato resistance to different pathogens, such as the potato late-blight pathogen P. infestans, the bacterial wilt pathogen Ralstonia solanacearum, and the gray-mold fungal pathogen Botrytis cinerea, we generated StMKK1 transgenic lines and investigated the response of potato transformants to destructive oomycete, bacterial, and fungal pathogens. The results showed that overexpression and silencing of StMKK1 do not alter plant growth and development. Interestingly, we found that StMKK1 negatively regulated potato resistance to the hemibiotrophic/biotrophic pathogens P. infestans and R. solanacearum, while it positively regulated potato resistance to the necrotrophic pathogen B. cinerea. Further investigation showed that overexpression of StMKK1 suppressed potato pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and salicylic acid (SA)-related responses, while silencing of StMKK1 enhanced PTI and SA-related immune responses. Taken together, our results showed that StMKK1 plays dual roles in potato defense against different plant pathogens via negative regulation of PTI and SA-related signaling pathways.

Highlights

Potato, the world’s third most important food crop (FAOSTAT 2013), is threatened by a group of major pathogens, Phytophthora infestans, Ralstonia solanacearum, and Botrytis cinerea
To determine whether StMKK1 is redundant in potato, we identified all MKK proteins in potato, tomato, and N. benthamiana and performed a phylogenetic analysis with Arabidopsis MKKs (Supplemental Fig. 1)
Several recent duplication events of MKK genes were found within both N. benthamiana and Arabidopsis, while no recent duplication was found in Solanum, i.e., potato and tomato

Summary

Introduction

The world’s third most important food crop (FAOSTAT 2013), is threatened by a group of major pathogens, Phytophthora infestans, Ralstonia solanacearum, and Botrytis cinerea. The biotrophic bacterial pathogen R. solanacearum causes one of the most notorious diseases of potato, known as potato bacterial wilt[3]. Potato gray mold is a common disease and is caused by the necrotrophic fungal pathogen B. cinerea[4]. These diseases lead to billions of dollars of potato production losses annually and pose serious threats to food security. The second layer is mediated by plant-resistance (R) proteins that can detect cognate pathogen effectors and subsequently activate a robust immune response called effector-triggered immunity (ETI)[7]

Methods

Results

Conclusion