title: Brassinosteroids alleviate high-temperature injury in Ficus concinna seedlings via maintaining higher antioxidant defence and glyoxalase systems.
abstract: Although brassinosteroids (BRs) play crucial roles in plant development and stress tolerance, the mechanisms by which they have these effects are poorly understood. Here, we investigated the possible mechanism of exogenously applied BRs on reactive oxygen species (ROS), antioxidant defence and methylglyoxal (MG) detoxification systems in Ficus concinna seedlings grown under high-temperature (HT) stress for 48 h. Our results showed that the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glyoxalase II (Gly II) were increased under two levels of HT stress. Compared with control the activities of catalase (CAT) and dehydroascorbate reductase (DHAR) were not changed due to HT stress. The activities of glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and glyoxalase I (Gly I) were increased only at moderate HT stress. Despite these protective mechanisms, HT stress induced oxidative stress in F. concinna seedlings, as indicated by the increased levels of ROS, malondialdehyde (MDA) and MG, and the reductions in chlorophyll levels and relative water content. The contents of reduced glutathione (GSH) and ascorbate (AsA) were not changed under moderate HT stress. Spraying with 24-epibrassinolide (EBR) alone had little influence on the non-enzymatic antioxidants and the activities of antioxidant enzymes. However, EBR pretreatment under HT stress resulted in an increase in GSH and AsA content, maintenance of high redox state of GSH and AsA, and enhanced ROS and MG detoxification by further elevating the activities of SOD, GST, GPX, APX, MDHAR, GR, DHAR, Gly I and Gly II, as evident by lower level of ROS, MDA and MG. It may be concluded that EBR could alleviate the HT-induced oxidative stress by increasing the enzymatic and non-enzymatic antioxidant defence, and glyoxalase systems in F. concinna seedlings.
authors.affiliation: Jiyang College, Zhejiang A & F University, Zhuji, Zhejiang Province 311800, China School of Forestry and Biotechnology, Zhejiang A & F University, Lin'an, Zhejiang Province 311300, China shjin@zafu.edu.cn.
authors.forename: Song Heng
authors.initials: SH
authors.lastname: Jin
authors.affiliation: Jiyang College, Zhejiang A & F University, Zhuji, Zhejiang Province 311800, China.
authors.forename: Xue Qin
authors.initials: XQ
authors.lastname: Li
authors.affiliation: Department of Forestry and Natural Resources, Clemson University, 226 Lehotsky Hall, Clemson, SC 29634-0317, USA.
authors.forename: G Geoff
authors.initials: GG
authors.lastname: Wang
authors.affiliation: Jiyang College, Zhejiang A & F University, Zhuji, Zhejiang Province 311800, China.
authors.forename: Xiang Tao
authors.initials: XT
authors.lastname: Zhu
keywords: Antioxidants; brassinosteroids; glyoxalase system; high-temperature stress; methylglyoxal