CaSTH2 disables CaWRKY40 from activating pepper thermotolerance and immunity against Ralstonia solanacearum via physical interaction

Xingge Cheng; Meiyun Wan; Yuqiu Song; Qian Liu; Xiaohui Hu; Xiufang Chen; Xujing Zhang; Yapeng Zhang; Ruijie Wu; Qiaoling Lu; Yu Huang; Jingang Lv; WeiWei Cai; Deyi Guan; Sheng Yang; Shuilin He

doi:10.1093/hr/uhae066

CaSTH2 disables CaWRKY40 from activating pepper thermotolerance and immunity against Ralstonia solanacearum via physical interaction

Hortic Res. 2024 Mar 2;11(5):uhae066. doi: 10.1093/hr/uhae066. eCollection 2024 May.

Authors

Xingge Cheng^{1

2

3}, Meiyun Wan^{1

2

3}, Yuqiu Song^{1

2

3}, Qian Liu^{1

2

4}, Xiaohui Hu^{1

2

3}, Xiufang Chen^{1

2

3}, Xujing Zhang^{1

2

4}, Yapeng Zhang^{1

2

3}, Ruijie Wu^{1

2

3}, Qiaoling Lu^{1

2

3}, Yu Huang^{1

2

3}, Jingang Lv^{1

2

3}, WeiWei Cai⁵, Deyi Guan^{1

2

3}, Sheng Yang^{1

6}, Shuilin He^{1

2

3}

Affiliations

¹ National Education Ministry Key Laboratory of Plant Genetic Improvement and Comprehensive Utilization, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
² Key Laboratory of Applied Genetics of Universities in Fujian Province, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
³ College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
⁴ College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
⁵ College of of Horticultural Sciences, Zhejiang Agriculture and Forestry University, Hangzhou, Zhejiang, 350002, China.
⁶ Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing, 100193, China.

Abstract

CaWRKY40 coordinately activates pepper immunity against Ralstonia solanacearum infection (RSI) and high temperature stress (HTS), forms positive feedback loops with other positive regulators and is promoted by CaWRKY27b/CaWRKY28 through physical interactions; however, whether and how it is regulated by negative regulators to function appropriately remain unclear. Herein, we provide evidence that CaWRKY40 is repressed by a SALT TOLERANCE HOMOLOG2 in pepper (CaSTH2). Our data from gene silencing and transient overexpression in pepper and epoptic overexpression in Nicotiana benthamiana plants showed that CaSTH2 acted as negative regulator in immunity against RSI and thermotolerance. Our data from BiFC, CoIP, pull down, and MST indicate that CaSTH2 interacted with CaWRKY40, by which CaWRKY40 was prevented from activating immunity or thermotolerance-related genes. It was also found that CaSTH2 repressed CaWRKY40 at least partially through blocking interaction of CaWRKY40 with CaWRKY27b/CaWRKY28, but not through directly repressing binding of CaWRKY40 to its target genes. The results of study provide new insight into the mechanisms underlying the coordination of pepper immunity and thermotolerance.