AN ESSENTIAL ROLE FOR NITRIC OXIDE IN AUXIN SIGNALING PATHWAY

TERRILE MC; CALDERON-VILLALOBOS L; IGLESIAS MJ; PARIS R; LAMATTINA L; ESTELLE M; CASALONGUÉ C

Puerto Madryn

Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecula; 2010

AN ESSENTIAL ROLE FOR NITRIC OXIDE IN AUXIN SIGNALING PATHWAY 1Terrile MC, 2Calderon-Villalobos LIA, 1Iglesias MJ, 1Paris R, 2Estelle M, 1Lamattina L and 1Casalongué C. 1IIB-CONICET-UNMdP Mar del Plata Argentina 2Division of Biological Sciences, University of California, USA. E-mail: mterrile@mdp.edu.ar Nitric oxide (NO) is a second messenger implicated in many plant cell signaling events. In particular, NO is a key molecule that operates in the auxin-regulated signaling cascade contributing to root morphogenesis during plant growth and development. S-nitrosylation is emerging as a specific posttranslational protein modification for the transduction of NO bioactivity. Recently, we demonstrated that NO production is induced in IAA-treated Arabidopsis roots. NO is also required for the auxin-induced gene expression and auxin-induced degradation of Aux/IAA repressors. Moreover, NO controls TIR1/AFB2-Aux/IAA protein-protein interaction leading to Aux/IAA degradation and auxin-dependent gene expression. Here, we demonstrate that the auxin receptor TIR1 is S-nitrosylated. Mutations of cysteine residues, Cys 140 (C140A) and Cys 480 (C480A) in TIR1 protein disrupted its interaction with Aux/IAA repressors. Arabidopsis transgenic lines overexpressing TIR1 protein in tir1-1 background rescued the normal root sensitivity to auxin. However, when tir1 C140A was overexpressed, TIR1 functionality was not recovered and seedlings remained resistant to auxin suggesting that S-nitrosylation of this cysteine residue may be critical for auxin signaling. These results open an exciting new field in the physiological regulation of auxin signaling by NO. Supported by UNMdP, ANPCyT, CONICET, UCSD-USA.