Both carbon monoxide (CO) and nitric oxide (NO) play fundamental roles in plant responses to environmental stress. Glutathione (GSH) homeostasis, achieved through the activity of the glutathione-ascorbate cycle, regulates cellular redox status to avoid the damage of reactive oxygen species (ROS) or reactive nitrogen species (RNS) to cellular components. Most recalcitrant seeds are sensitive to chilling stress and respond poorly to the associated accumulation of ROS, but the roles of CO, NO and GSH in recalcitrant seeds in response to low temperature is not well understood.
Recently, LI Duzhu’s group, HU Xiangyang’s group and YANG Yongping’s group from Kunming Institute of Botany report that the germination of recalcitrant seeds from Baccaurea ramiflora show sensitive to chilling stress, but exogenous CO or NO application markedly increased GSH accmulation, enhanced the activities of antioxidant enzymes involved in glutathione-ascorbate cycle, decreased the contents of H2O2 and RNS, as well as improving the seeds tolerance to low temperature stress. Comparing the orthodox seeds such as maize seeds, the recalcitrant B.ramiflora seeds only induced the transient accumulations of CO and NO, and inadequate increase of GSH under chilling. Exogenously CO or NO treatment further increased the GSH accumulation and S-nitrosogluthathione reductase (GSNOR) activity in B.ramiflora seeds under chilling stress; In contrast, suppressing CO or NO generation, removing GSH or blocking GSNOR activity resulted into the increases of ROS and RNS, and impaired CO- or NO-induced seeds germination under chilling stress. Basing on these results, it is proposed that CO acts as a novel regulator to improve recalcitrant seeds tolerance to low temperature through NO-mediated glutathione homeostasis.
This work is online published by Free Radical Biology & Medicine (http://www.sciencedirect.com/science/article/pii/S0891584912002997?v=s5), and supported by 100 Talents Program of the Chinese Academy of Sciences and by grants from the National Science Foundation of China.
Effects of CO, NO and their corresponding inhibitors on the germination of Baccaurea ramiflora seeds following low temperature treatment. (Image by KIB)
Effect of CO and different scavengers/inhibitors on chilling induced NO fluorescence in Baccaurea ramiflora. (Image by KIB)
