Horticulture Research

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Article|29 Dec 2023|OPEN

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

Shaoyun Dong¹ ^,† , Xin Liu¹ ^,† , Jianan Han¹ ^,† , Han Miao¹ ^,† , Diane M. Beckles² , Yuling Bai³ , Xiaoping Liu¹ , Jiantao Guan¹ , Ruizhen Yang⁴ , Xingfang Gu¹ , Jiaqiang Sun⁴ ^, , Xueyong Yang¹ ^, and Shengping Zhang,¹ ^,

¹State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, 100081, Beijing China
²Department of Plant Sciences, University of California Davis, One Shield Avenue, Davis, CA 95616, USA
³Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
⁴Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, 100081 Beijing, China
*Corresponding author. E-mail: sunjiaqiang@caas.cn,yangxueyong@caas.cn,zhangshengping@caas.cn
^†Shaoyun Dong,Xin Liu,Jianan Han and Han Miao contributed equally to the study.

Horticulture Research 11,
Article number: uhad295 (2024)
doi: https://doi.org/10.1093/hr/uhad295
Views: 61

Received: 05 Aug 2023
Accepted: 20 Dec 2023
Published online: 29 Dec 2023

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.