The Arabidopsis J-protein AtDjB1 facilitates thermotolerance by protecting cells against heat-induced oxidative damage

• Published in: The New phytologist 2012-04, Vol.194 (2), p.364-378
• Main Authors: Zhou, Wei, Zhou, Ting, Li, Mi‐Xin, Zhao, Chun‐Lan, Jia, Ning, Wang, Xing‐Xing, Sun, Yong‐Zhen, Li, Guo‐Liang, Xu, Meng, Zhou, Ren‐Gang, Li, Bing
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - drug effects; Adenosine triphosphatase; Adenosine triphosphatases; Adenosine Triphosphate - metabolism; Arabidopsis; Arabidopsis - cytology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; ascorbate (ASC); Ascorbic acid; Ascorbic Acid - pharmacology; AtDjB1; ATP; Cell death; Cell Respiration - drug effects; Cells; Cytoprotection - drug effects; Damage; Gene Expression Regulation, Plant - drug effects; Gene Knockout Techniques; Genetic analysis; Heat shock; Heat shock proteins; Heat stress; Heat tolerance; Heat-Shock Response - drug effects; Homeostasis; Hot Temperature; HSP40 Heat-Shock Proteins - genetics; HSP40 Heat-Shock Proteins - metabolism; HSP70 Heat-Shock Proteins - metabolism; Hydrogen peroxide; hydrogen peroxide (H2O2); Hydrogen Peroxide - metabolism; Hydrogen Peroxide - pharmacology; Mitochondria; Mitochondrial Proteins - metabolism; Mutation - genetics; Organ Specificity - drug effects; Organ Specificity - genetics; oxidative damage; Oxidative stress; Oxidative Stress - drug effects; Oxidoreductions; Phenotype; Plant physiology; Plants; Protein Binding - drug effects; Protein Transport - drug effects; Proteins; Respiration; Seedlings; Seedlings - drug effects; Subcellular Fractions - drug effects; Subcellular Fractions - metabolism; Survival rates; Temperature tolerance; thermotolerance; Yeasts
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2012.04070.x

AtDjB1 belongs to the J-protein family in Arabidopsis thaliana. Its biological functions in plants are largely unknown. In this study, we examined the roles of AtDjB1 in resisting heat and oxidative stresses in A. thaliana using reverse genetic analysis. AtDjB1 knockout plants (atj1-1) were more sensitive to heat stress than wildtype plants, and displayed decreased concentrations of ascorbate (ASC), and increased concentrations of hydrogen peroxide (H2O2) and oxidative products after heat shock. Application of H2O2 accelerated cell death and decreased seedling viability in atj1-1. Exogenous ASC conferred much greater thermotolerance in atj1-1 than in wildtype plants, suggesting that a lower concentration of ASC in atj1-1 could be responsible for the increased concentration of H2O2 and decreased thermotolerance. Furthermore, AtDjB1 was found to localize to mitochondria, directly interact with a mitochondrial heat-shock protein 70 (mtHSC70-1), and stimulate ATPase activity of mtHSC70-1. AtDjB1 knockout led to the accumulation of cellular ATP and decreased seedling respiration, indicating that AtDjB1 modulated the ASC concentration probably through affecting the function of mitochondria. Taken together, these results suggest that AtDjB1 plays a crucial role in maintaining redox homeostasis, and facilitates thermotolerance by protecting cells against heat-induced oxidative damage.