The alternative respiratory pathway is involved in brassinosteroid-induced environmental stress tolerance in Nicotiana benthamiana

• Published in: Journal of experimental botany Vol. 66; no. 20; pp. 6219 - 6232
• Main Authors: Deng, Xing-Guang, Zhu, Tong, Zhang, Da-Wei, Lin, Hong-Hui
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.10.2015
• Subjects: Brassinosteroids - pharmacology; Cold Temperature; Light; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; Nicotiana - drug effects; Nicotiana - genetics; Nicotiana - metabolism; Oxidoreductases - genetics; Oxidoreductases - metabolism; Plant Growth Regulators - pharmacology; Plant Proteins - genetics; Plant Proteins - metabolism; Polyethylene Glycols - pharmacology; Reactive Oxygen Species - metabolism; RESEARCH PAPER; Signal Transduction; Steroids, Heterocyclic - pharmacology; Stress, Physiological; Triazoles - pharmacology; Nicotiana benthamiana; stress tolerance; Alternative oxidase; brassinosteroids; reactive oxygen species
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erv328

Brassinosteroids (BRs), plant steroid hormones, play essential roles in modulating cell elongation, vascular differentiation, senescence, and stress responses. However, the mechanisms by which BRs regulate plant mitochondria and resistance to abiotic stress remain largely unclear. Mitochondrial alternative oxidase (AOX) is involved in the plant response to a variety of environmental stresses. In this report, the role of AOX in BR-induced tolerance against cold, polyethylene glycol (PEG), and high-light stresses was investigated. Exogenous applied brassinolide (BL, the most active BR) induced, while brassinazole (BRZ, a BR biosynthesis inhibitor) reduced alternative respiration and AOX1 expression in Nicotiana benthamiana. Chemical scavenging of H₂O₂ and virus-induced gene silencing (VIGS) of NbRBOHB compromised the BR-induced alternative respiratory pathway, and this result was further confirmed by NbAOX1 promoter analysis. Furthermore, inhibition of AOX activity by chemical treatment or a VIGS-based approach decreased plant resistance to environmental stresses and compromised BR-induced stress tolerance. Taken together, our results indicate that BR-induced AOX capability might contribute to the avoidance of superfluous reactive oxygen species accumulation and the protection of photosystems under stress conditions in N. benthamiana.