CaZAT11 Negatively Fine-Tunes Pepper Immunity to Ralstonia solanacearum by Repressing CaHDZ27

Plant immunity against pathogens is largely regulated at the transcriptional level by various transcription factors. In pepper, CaHDZ27 positively regulates immunity against Ralstonia solanacearum. However, the mechanisms that fine-tune this CaHDZ27-mediated immunity remain elusive. Here, we report that CaHDZ27 interacted with CaZAT11, a C2H2-type zinc finger transcription factor harbouring an EAR repression motif. Silencing of CaZAT11 significantly reduced susceptibility to R. solanacearum without impairing plant growth, whereas its overexpression promoted growth of Nicotiana benthamiana but compromised its immunity against R. solanacearum. We further found that CaZAT11 acted as a transcriptional repressor suppressing the transcriptional activity of CaHDZ27 under basal conditions. Upon infection with R. solanacearum, however, CaHDZ27 dissociated from CaZAT11 and instead interacted with the 14-3-3 protein CaTFT7. This interaction released CaHDZ27 from repression, which in turn enabled the activation of downstream immune responses. Collectively, our study identified CaZAT11 as a central regulatory node in the plant immunity network, modulating the critical trade-off between growth and defence.