Poster: Hormones

Abs # 582: Auxin and nitric oxide cross talk in the development of root architecture

Presenter:	Graziano, Magdalena
Authors	Graziano, Magdalena  (A)   Correa-Aragunde, Natalia  (A)   Lamattina, Lorenzo  (A)
Affiliations:	(A): Instituto de Investigaciones Biologicas, Universidad Nacional de Mar del Plata, CC 1245, 7600-Mar del Plata, Argentina.

Nitric oxide (NO) is a bioactive molecule that functions in numerous physiological processes in plants, most of them involving a cross talk with traditional phytohormones. Auxin is the main hormone that regulates root system architecture. In this communication we report that NO promotes lateral root (LR) development and controls primary root (PR) growth, two auxin-dependent processes. Application of the NO donor sodium nitroprusside (SNP) to tomato (Lycopersicon esculentum) seedlings induced LR emergence and elongation in a dose-dependent manner, while PR growth was inhibited. A 2.5-fold increase in LR number was reached with 200 mM SNP, which releases approximately 1.4 nM.s^-1 NO. The effect is specific for NO since the NO scavenger 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO) blocked the action of SNP. Depletion of endogenous NO with CPTIO resulted in a complete abolishment of LR emergence and a 40 % increase in PR length. This result suggests a physiological role for NO on the regulation of root system growth. In another set of experiments, it was found that root branching and shortening induced by the synthetic auxin 1-naphthylacetic acid (NAA) was prevented by CPTIO in a dose-dependent manner. Moreover, SNP was able to promote LR development in auxin-depleted seedlings treated with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). All together, these results suggest a novel role for NO in the regulation of root system architecture, probably operating in the auxin signaling transduction pathway. Supported by: ANPCyT, CONICET, UNMdP, Fundación Antorchas.