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 (TGA1) and TGA4 in regulating SA and Pip biosynthesis in Arabidopsis thaliana. We quantified the expression levels of SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) and CALMODULIN-BINDING PROTEIN 60g (CBP60g), 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 SARD1 and CBP60g are direct targets of TGA1 by chromatin immunoprecipitation−polymerase chain reaction (ChIP-PCR). In addition to promoting pathogen-induced SA biosynthesis, we found that SARD1 and CBP60g also positively regulated Pip biosynthesis by targeting genes encoding key biosynthesis enzymes of Pip. TGA1/TGA4 were required for full induction of SARD1 and CBP60g in plant defense. ChIP-PCR analysis showed that SARD1 was a direct target of TGA1. In tga1-1 tga4-1 mutant plants, the expression levels of SARD1 and CBP60g along with SA and Pip accumulation following pathogen infection were dramatically reduced compared with those in wild-type plants. Consistent with reduced expression of SARD1 and CBP60g, pathogen-associated molecular pattern (PAMP)-induced pathogen resistance and systemic acquired resistance were compromised in tga1-1 tga4-1. Our study showed that TGA1 and TGA4 regulate Pip and SA biosynthesis by modulating the expression of SARD1 and CBP60g.
Bibliographical noteFunding Information:
We thank Dr Xin Li from the University of British Columbia (UBC) for careful reading of the manuscript and Ms Yuling Sun (UBC) for help with Pip measurement. The Natural Sciences and Engineering Research Council (NSERC) of Canada and Canada Foundation for Innovation (CFI) are thanked for their financial support of Y.Z. The authors have no conflict of interest to declare.
- CALMODULIN-BINDING PROTEIN 60g (CBP60g)
- SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1)
- TGACG-BINDING FACTOR 1 (TGA1)
- TGACG-BINDING FACTOR 4 (TGA4)
- pipecolic acid (Pip)
- plant immunity
- salicylic acid (SA)