Pharmacological and genetical evidence supporting nitric oxide requirement for 2,4-epibrassinolide regulation of root architecture in Arabidopsis thaliana

Abstract

Brassinosteroids (BRs) regulate various physiological processes, such as tolerance to stresses and root growth. Recently, a connection was reported between BRs and nitric oxide (NO ) in plant responses to abiotic stress. Here we present evidence supporting NO functions in BR signaling during root growth process. Arabidopsis seedlings treated with BR 24-epibrassinolide (BL) show increased lateral roots (LR) density, inhibition of primary root (PR) elongation and NO accumulation. Similar effects were observed adding the NO donor GSNO to BR-receptor mutant bri1-1. Furthermore, BL induced responses in the root were abolished by the specific NO scavenger c-PTIO . The activities of nitrate reductase (NR )and nitric oxide synthase (NOS)-like, two NO generating enzymes were involved in BR signaling. These results demonstrate that BR increases the NO concentration in root cells, which is required for BR-induced changes in root architecture.