Redox agents modulate class I TCP transcription factor action in plants

VIOLA IVANA; GÜTTLEIN LEANDRO; GONZALEZ DANIEL

Mendoza

Congreso; XLVIII Reunión Anual de la SAIB; 2012

SAIB

TCP transcription factors are regulators of plant cell growth and proliferation that contain the TCP domain, a basic helix-loop-helix structure required for DNA binding and dimerization. These proteins can be grouped in two major classes, I and II. In this work, we identified a highly conserved Cys residue in helix I of class I TCP proteins and we show that several redox agents reversibly modulate the capacity of Cys20-containing class I proteins to interact with DNA. Mutation of Cys20 to Ser in the class I protein TCP15 abolished its redox sensitivity. Under oxidizing conditions, covalently linked dimers were formed, suggesting that inactivation is associated with the formation of intermolecular disulfide bonds. Inhibition of class I TCP protein activity was also observed in vivo, in yeast cells expressing TCP proteins and in plants after treatment with redox agents. Modeling studies suggest that Cys20 is probably located at the dimer interface near the DNA binding surface and explains the sensitivity of DNA binding to oxidation of Cys20. The redox properties of Cys20 and the observed effect of cellular redox agents both in vitro and in vivo suggest that class I TCP protein action is under redox control in plants.