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

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.

Acknowledgements

We thank Mark D. Curtis for kindly providing the Gateway destination vectors, Dr S. P. Dinesh-Kumar of Yale University for the pTRV1 and pTRV2 vectors. This work was supported by grants from the National Natural Science Foundation of China (31902032, 31572136, 31372061) and Development Fund Project of Fujian Agriculture and Forestry University (CXZX2016158, CXZX2017548).

Author contributions

S.H. and Xin.C. designed the research. M.W., Q.L., J.L., Y.S., and X.H. performed the experiments. S.Y., Y.Z., Y.H., R.W., and D.G. analysed the data. S.H. wrote the manuscript. All the authors of this paper read and approved the final manuscript.

Data availability

The data that support the findings of this study are available in the Supporting Information.

Conflict of interest statement

The authors declare that they have no conflicts of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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