Abstract
BackgroundBrassinolide (BR), as a new type of plant hormones, is involved in the processes of plant growth and stress response. Previous studies have reported the roles of BR in regulating plant developmental processes and also response tolerance to abiotic stresses in plants. The main purpose of our study was to explore whether nitric oxide (NO) plays a role in the process of BR-induced adventitious root formation in cucumber (Cucumis sativus L.).ResultsExogenous application of 1 μM BR significantly promoted adventitious rooting, while high concentrations of BR (2–8 μM) effectively inhibited adventitious rooting. NO donor (S-nitroso-N-acerylpenicillamine, SNAP) promoted the occurrence of adventitious roots. Simultaneously, BR and SNAP applied together significantly promoted adventitious rooting and the combined effect was superior to the application of BR or SNAP alone. Moreover, NO scavenger (c-PTIO) and inhibitors (L-NAME and Tungstate) inhibited the positive effects of BR on adventitious rooting. BR at 1 μM also increased endogenous NO content, NO synthase (NOS-like) and Nitrate reductase (NR) activities, while BRz (a specific BR biosynthesis inhibitor) decreased these effects. In addition, the relative expression level of NR was up-regulated by BR and SNAP, whereas BRz down-regulated it. The application of NO inhibitor (Tungstate) in BR also inhibited the up-regulation of NR.ConclusionBR promoted the formation of adventitious roots by inducing the production of endogenous NO in cucumber.
Highlights
Brassinolide (BR), as a new type of plant hormones, is involved in the processes of plant growth and stress response
Zhao et al [9] found that exogenous EBR application ameliorated the inhibitory effects of photosynthesis, antioxidant enzyme activity and Rubisco activase (RCA) gene expression in Triticum aestivum induced by a combination of drought and heat stress
The results showed that exogenous BR enhanced the number and length of adventitious root at low concentrations, while high concentrations of BR treatments suppressed adventitious root development (Fig. 1), which suggested that the effect of BR on adventitious root is a dose-dependent response
Summary
Brassinolide (BR), as a new type of plant hormones, is involved in the processes of plant growth and stress response. Previous studies have reported the roles of BR in regulating plant developmental processes and response tolerance to abiotic stresses in plants. The main purpose of our study was to explore whether nitric oxide (NO) plays a role in the process of BR-induced adventitious root formation in cucumber (Cucumis sativus L.). Brassinolide (BR), a new plant hormone, was first discovered during the screening of pollen grains [1]. It plays an important role in regulating various developmental processes, including root and hypocotyl elongation [2]. Yuan et al [8] reported that the application of 2,4-Epibrassinolide (EBL) alleviated Ca(NO3) stress in cucumber plants by regulating mineral nutrients uptake and distribution. Low concentration of BR was suitable for callus growth and shoot regeneration in Spartina patens [10], while high concentration of epibrassinolide inhibited
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