NITRIC OXIDE IS REQUIRED FOR THE BRASSINOSTEROID REGULATION OF ROOT GROWTH AND STOMATAL APERTURE.

TOSSI, V; LAMATTINA, L.; CASSIA, R.

Potrero de los Funes

Congreso; XLVII Reunion anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).; 2011

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).

Nitric oxide is required for the brassinosteroid regulation of root growth and stomatal aperture Vanesa Tossi , Lorenzo Lamattina+ and Raúl Cassia Genetic and pharmacological evidence supporting nitric oxide (NO) involvement in brassinosteroids (BR) signaling is presented. Arabidopsis seedlings treated with BR 24-epibrassinolide (BL) show increased lateral roots (LR) density, primary root (PR) inhibition and NO accumulation. BL-induced responses were abolished by specific NO scavenger c-PTIO, confirming NO participation in BL signaling.  The nitrate reductase (NR) mutant nia1-2 is partially insensitive to BL and NO synthase (NOS) inhibitor L-NAME addition abolished BL effect over root morphology. The lack of BL response in BR-receptor mutant bri1-1 is reverted by NO donor GSNO addition, indicating that NO acts downstream BR. The distribution of the auxin efflux carriers PIN1 and PIN2 is affected by BL in a NO-independent pathway, suggesting that NO acts downstream of auxins. NR and NOS-like activities are required for BL-dependent NO accumulation in guard cells and full BL-induced response of stomatal closure. Stomata from aba3-1 (deficient in ABA synthesis) were insensitive to BL, indicating that ABA is required for BL-induced NO production. This demonstrates that: (i) BL increases the NO concentration in roots and guard cells in a BR receptor, NR- and NOS-like-dependent pathway and (ii) NO is required for BR-induced changes leading to altered root architecture and stomatal closure.