CsMLO8/11 are required for full susceptibility of cucumber stem to powdery mildew and interact with CsCRK2 and CsRbohD

Shaoyun Dong; Xin Liu; Jianan Han; Han Miao; Diane M Beckles; Yuling Bai; Xiaoping Liu; Jiantao Guan; Ruizhen Yang; Xingfang Gu; Jiaqiang Sun; Xueyong Yang; Shengping Zhang

doi:10.1093/hr/uhad295

CsMLO8/11 are required for full susceptibility of cucumber stem to powdery mildew and interact with CsCRK2 and CsRbohD

Hortic Res. 2023 Dec 29;11(2):uhad295. doi: 10.1093/hr/uhad295. eCollection 2024 Feb.

Authors

Affiliations

¹ State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 100081, Beijing China.
² Department of Plant Sciences, University of California Davis, One Shield Avenue, Davis, CA 95616, USA.
³ Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
⁴ Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, 100081 Beijing, China.

Abstract

Powdery mildew (PM) is one of the most destructive diseases that threaten cucumber production globally. Efficient breeding of novel PM-resistant cultivars will require a robust understanding of the molecular mechanisms of cucumber resistance against PM. Using a genome-wide association study, we detected a locus significantly correlated with PM resistance in cucumber stem, pm-s5.1. A 1449-bp insertion in the CsMLO8 coding region at the pm-s5.1 locus resulted in enhanced stem PM resistance. Knockout mutants of CsMLO8 and CsMLO11 generated by CRISPR/Cas9 both showed improved PM resistance in the stem, hypocotyl, and leaves, and the double mutant mlo8mlo11 displayed even stronger resistance. We found that reactive oxygen species (ROS) accumulation was higher in the stem of these mutants. Protein interaction assays suggested that CsMLO8 and CsMLO11 could physically interact with CsRbohD and CsCRK2, respectively. Further, we showed that CsMLO8 and CsCRK2 competitively interact with the C-terminus of CsRbohD to affect CsCRK2-CsRbohD module-mediated ROS production during PM defense. These findings provide new insights into the understanding of CsMLO proteins during PM defense responses.