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S2.5: Regulation of the plant defense responses by class I TGA transcription factors and interacting CC-type glutaredoxins

Christiane Gatz & Yuelin Zhang
PhD student: Anja Pelizaeus

Pathogen attack leads to major changes in gene expression to favor anti-stress processes over normal cellular functions. The activation or in-activation of pre-existing transcription factors by cellular signaling cascades is a crucial step in this process. Transcription factor TGA1 activates genes involved in the biosynthesis and catabolim of two major defense hormones, namely salicylic acid (SA) and N-hydroxy-pipecolic acid (NHP) (Sun et al., 2018; Budimir et al., 2020, manuscript in preparation). The SA receptor NPR1 is a crucial transcriptional activator of TGA transcription factors.












TGA transcription factors do not only interact with NPR1, but also with land plant-specific glutaredoxins (called ROXYs in Arabidopsis thaliana). Glutaredoxins are small proteins that can either oxidize thiol groups of cysteines or reduce disulfide bridges and have thus the potential to regulate protein activities. Arabidopsis encodes 21 ROXY genes. Ectopic expression of ROXY9 interferes with TGA1 function (Li et al., 2018), while ectopic expression of ROXY19 interferes with the function of TGA2. ROXY9 acts most likely redundantly with ROXY6, 7, 8 and 9. In preparation of this project, we have generated a roxy6 roxy7 roxy8 roxy9 quadruple mutant. Our aim is to characterize the phenotype of this mutant and to elucidate the mechanism how this clade of ROXYs interferes with the function of TGA1.

The project is done in close collaboration with Prof. Yuelin Zhang at UBC Vancouver who is an expert in the elucidation of transcriptional control mechanisms in plant defense responses.

Li N, Muthreich M, Huang LJ, Thurow C, Sun T, Zhang Y, Gatz C. 2018. TGACG-BINDING FACTORs (TGAs) and TGA-interacting CC-type glutaredoxins modulate hyponastic growth in Arabidopsis thaliana. New Phytol. 2018 Sep 25. doi: 10.1111/nph.15496. (This work describes the genetic and physical interaction between ROXY9 and TGA1, which is different from the role of ROXYs 11-15)

Sun T, Busta L, Zhang Q, Ding P, Jetter R, Zhang Y. 2018. TGACG-BINDING FACTOR 1 (TGA1) and TGA4 regulate salicylic acid and pipecolic acid biosynthesis by modulating the expression of SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) and CALMODULIN-BINDING PROTEIN 60g (CBP60g). New Phytol 217, 344-354.


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