Nitric oxide is involved in brassinosteroid‐induced alternative respiratory pathway in Nicotiana benthamiana seedlings' response to salt stress

Abstract

Recent studies reported that brassinosteroids (BRs) can induce plant tolerance to different environmental stresses via the nitric oxide (NO) signaling pathway. Previous reports have indicated that alternative oxidase (AOX) plays an important role in plants under various stresses. The mechanisms governing how NO is involved as a signal molecule which connects BR with AOX in regulating stress tolerance are still unknown. Recently, we found that Nicotiana benthamiana seedlings which were pretreated with BR have more tolerance to salt stress, accompanied with an increase of CN-resistant respiration. Our results suggested that pretreatment with 0.1 μM brassinolide (BL, the most active brassinosteroid) alleviated salt-induced oxidative damage and increased the NbAOX1 transcript level. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-1-oxyl-3-oxide (cPTIO, an NO scavenger) or virus-induced gene silencing of nitrate reductase (NR) and nitric oxide synthase (NOS)-like enzyme compromised the BRs-induced alternative respiratory pathway. Furthermore, pretreatment with specific chemical inhibitors of NR and NOS or gene silencing experiments decreased plant resistance to salt stress which also compromised BRs-induced salt stress tolerance. In conclusion, NO is involved in BRs-induced AOX capability which plays essential roles in salt tolerance in N. benthamiana seedlings.

Mitochondrial alternative oxidase‐dependent autophagy involved in ethylene‐mediated drought tolerance in Solanum lycopersicum

“…Respiratory rate and chlorophyll fluorescence were measured using Clark‐type electrodes (Hansatech, King's Lynn, UK) and an imaging pulse amplitude‐modulated fluorometer (IMAG‐MINI, Heinz Walz, Germany) according to Zhu et al . (,b).…”

Brassinosteroids: A Promising Option in Deciphering Remedial Strategies for Abiotic Stress Tolerance in Rice

“…It was found that BR application results in increase in cytosolic Ca (2+) concentration followed by increase in activity of CCaMK which further enhanced the BR-induced increase in cytosolic Ca (2+) concentration thus forming a positive feedback loop of Ca (2+) and CCaMK in BR signaling ( Yan et al, 2015 ). ABA has also been demonstrated to be intricately involved in BR-orchestrated antioxidant defense via ZmMAP65-1a as inhibition of ABA biosynthesis reduces the expression and activity of ZmMAP65-1a ( Zhu et al, 2015 ). The BR-induced pulse of H 2 O 2 production via NADPH oxidase results in enhanced ABA biosynthesis, which results in further escalation of H 2 O 2 levels leading to prolonged stress tolerance ( Zhou et al, 2014 ).…”

“…Inhibition of NO production is found to inhibit BR-induced stress tolerance and partly blocks BR-induced expression and activities of various antioxidant enzymes ( Cui et al, 2011 ; Zhang et al, 2011 ). Gene silencing or chemical inhibition of nitrate reductase (NR) and nitric oxide synthase (NOS)-like enzyme inhibits the BRs-induced alternative respiratory pathway and thus decreased plant’s resistance to salt stress ( Zhu et al, 2015 ). On the other hand, BRs induce NO production in a ROS dependent manner via both NOS-like and nitrate/nitrite dependent enzymatic routes ( Zhang et al, 2010 ; Yang et al, 2013 ) and NO in turn mediates induction of antioxidant genes, for mitigating oxidative stress conditions ( Zhang et al, 2010 ).…”

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