Tomaž, Š., et al. 2023. Plant Physiology

A mini-TGA protein modulates gene expression through heterogeneous association with transcription factors

Špela Tomaž, Marko Petek, Tjaša Lukan, Karmen Pogačar, Katja Stare, Erica Teixeira Prates, Daniel A Jacobson, Jan Zrimec, Gregor Bajc, Matej Butala, Maruša Pompe Novak, Quentin Dudley, Nicola Patron, Ajda Taler-Verčič, Aleksandra Usenik, Dušan Turk, Salomé Prat, Anna Coll, and Kristina Gruden
December 15, 2022, Plant Physiology; DOI: 10.1093/plphys/kiac579


TGA (TGACG-binding) transcription factors, which bind their target DNA through a conserved basic region leucine zipper (bZIP) domain, are vital regulators of gene expression in salicylic acid (SA)-mediated plant immunity. Here, we investigated the role of StTGA2.1, a potato (Solanum tuberosum) TGA lacking the full bZIP, which we named a mini-TGA. Such truncated proteins have been widely assigned as loss-of-function mutants. We, however, confirmed that StTGA2.1 overexpression compensates for SA-deficiency, indicating a distinct mechanism of action compared with model plant species. To understand the underlying mechanisms, we showed that StTGA2.1 can physically interact with StTGA2.2 and StTGA2.3, while its interaction with DNA was not detected. We investigated the changes in transcriptional regulation due to StTGA2.1 overexpression, identifying direct and indirect target genes. Using in planta transactivation assays, we confirmed that StTGA2.1 interacts with StTGA2.3 to activate StPRX07, a member of class III peroxidases (StPRX), which are known to play role in immune response. Finally, via structural modeling and molecular dynamics simulations, we hypothesized that the compact molecular architecture of StTGA2.1 distorts DNA conformation upon heterodimer binding to enable transcriptional activation. This study demonstrates how protein truncation can lead to distinct functions and that such events should be studied carefully in other protein families.


Tomaž, Š., Petek, M., Lukan, T., Pogačar, K., Stare, K., Teixeira Prates, E., Jacobson, D. A., Zrimec, J., Bajc, G., Butala, M., Pompe Novak, M., Dudley, Q., Patron, N., Taler-Verčič, A., Usenik, A., Turk, D., Prat, S., Coll, A., & Gruden, K. (2023). A mini-TGA protein modulates gene expression through heterogeneous association with transcription factors. Plant Physiology. Volume 191, Issue 3, March 2023, Pages 1934–1952.