Abstract
Recognition of pathogens by host plants leads to rapid transcriptional reprogramming and activation of defence responses. The expression of many defence regulators is induced in this process, but the mechanisms of how they are controlled transcriptionally are largely unknown. Here we use chromatin immunoprecipitation sequencing to show that the transcription factors SARD1 and CBP60g bind to the promoter regions of a large number of genes encoding key regulators of plant immunity. Among them are positive regulators of systemic immunity and signalling components for effector-triggered immunity and PAMP-triggered immunity, which is consistent with the critical roles of SARD1 and CBP60g in these processes. In addition, SARD1 and CBP60g target a number of genes encoding negative regulators of plant immunity, suggesting that they are also involved in negative feedback regulation of defence responses. Based on these findings we propose that SARD1 and CBP60g function as master regulators of plant immune responses.
Highlights
Recognition of pathogens by host plants leads to rapid transcriptional reprogramming and activation of defence responses
Quantitative reverse transcription PCR (RT–PCR) analysis showed that the expression of Isochorismate Synthase 1 (ICS1) in snc2-1D is much higher than in wild type, but the increased expression of ICS1 is blocked in the sard[1] cbp60g-1 snc2-1D triple mutant (Fig. 1a)
Quantitative RT–PCR analysis showed that the expression levels of defence marker genes PR1 and PR2 are slightly lower in the double mutants but are markedly reduced in the triple mutant compared with snc2-1D (Fig. 1d,e)
Summary
Recognition of pathogens by host plants leads to rapid transcriptional reprogramming and activation of defence responses. We use chromatin immunoprecipitation sequencing to show that the transcription factors SARD1 and CBP60g bind to the promoter regions of a large number of genes encoding key regulators of plant immunity. SARD1 and CBP60g target a number of genes encoding negative regulators of plant immunity, suggesting that they are involved in negative feedback regulation of defence responses. Two pathogen-induced transcription factors, SAR DEFICIENT1 (SARD1) and CAM-BINDING PROTEIN 60-LIKE G (CBP60g), regulate the expression of ICS1 and are required for pathogen induction of SA synthesis[23,24,25]. SARD1 and CBP60g belong to the same protein family but are regulated differently, suggesting that they function in two parallel pathways to activate ICS1 expression[23,24]. Overexpression of SARD1, but not CBP60g, leads to constitutive activation of defence responses
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