TGACG ‐ BINDING FACTOR 1 ( TGA 1) and TGA 4 regulate salicylic acid and pipecolic acid biosynthesis by modulating the expression of SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 ( SARD 1 ) and CALMODULIN ‐ BINDING PROTEIN 60g ( CBP 60g )

Summary Salicylic acid ( SA ) and pipecolic acid (Pip) play important roles in plant immunity. Here we analyzed the roles of transcription factors TGACG ‐ BINDING FACTOR 1 ( TGA 1) and TGA 4 in regulating SA and Pip biosynthesis in Arabidopsis thaliana . We quantified the expression levels of SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 ( SARD 1 ) and CALMODULIN‐ BINDING PROTEIN 60g ( CBP 60g ), which encode two master transcription factors of plant immunity, and the accumulation of SA and Pip in tga1‐1 tga4‐1 mutant plants. We tested whether SARD 1 and CBP 60g are direct targets of TGA 1 by chromatin immunoprecipitation−polymerase chain reaction (Ch IP ‐ PCR ). In addition to promoting pathogen‐induced SA biosynthesis, we found that SARD 1 and CBP 60g also positively regulated Pip biosynthesis by targeting genes encoding key biosynthesis enzymes of Pip. TGA 1/ TGA 4 were required for full induction of SARD 1 and CBP 60g in plant defense. Ch IP ‐ PCR analysis showed that SARD 1 was a direct target of TGA 1. In tga1‐1 tga4‐1 mutant plants, the expression levels of SARD 1 and CBP 60g along with SA and Pip accumulation following pathogen infection were dramatically reduced compared with those in wild‐type plants. Consistent with reduced expression of SARD 1 and CBP 60g , pathogen‐associated molecular pattern ( PAMP )‐induced pathogen resistance and systemic acquired resistance were compromised in tga1‐1 tga4‐1 . Our study showed that TGA 1 and TGA 4 regulate Pip and SA biosynthesis by modulating the expression of SARD 1 and CBP 60g .