Control of salicylic acid synthesis and systemic acquired resistance by two members of a plant-specific family of transcription factors

摘要

Salicylic acid (SA) is a defense hormone required for both local and systemic acquired resistance (SAR) in plants. Pathogen infections induce SA synthesis through up-regulating the expression oflsochor-ismate Synthase 1 (ICS1), which encodes a key enzyme in SA produc-tion. Here we report that both SAR Deficient 1 (SARD1) and CBP60g are key regulators for ICS1 induction and SA synthesis. Whereas knocking out SARD1 compromises basal resistance and SAR, over-expression of SARD1 constitutively activates defense responses. In the sard1-1 cbp60g-1 double mutant pathogen-induced ICS1 up-regulation and SA synthesis are blocked in both local and systemic leaves, resulting in compromised basal resistance and loss of SAR. Electrophoretic mobility shift assays showed that SARD1 and CBP60g represent a plant-specific family of DNA-binding proteins. Both pro-teins are recruited to the promoter of ICS1 in response to pathogen infections, suggesting that they control SA synthesis by regulating ICS1 at the transcriptional level.