Hydrogen sulfide enhances poplar tolerance to high-temperature stress by increasing S-nitrosoglutathione reductase (GSNOR) activity and reducing reactive oxygen/nitrogen damage

Poplar (Populus trichocarpa) is an important woody tree for landscape and agricultural use worldwide. Nitric oxide (NO) and hydrogen sulfide (H2S) are essential messengers that enhance tolerance to environmental stress in herbaceous plants; however, the role of these messengers in modifying environmental stress in woody plants is poorly understood. Here we found that high temperature (HT) rapidly induced the generation of H2S, accompanied by increased activity of enzymes involved in H2S biosynthesis. HT also induced the accumulation of reactive nitrogen species (RNS) and reactive oxygen species (ROS), including S-nitrosothiols, H2O2, and O-2 (-), which damage the leaves. S-nitrosoglutathione reductase (GSNOR) has a critical role in preventing RNS and ROS damage in plants. We found that HT gradually increased the transcriptional level and the activity of GSNOR, resulting in increased scavenging of the over-accumulated ROS and RNS and, ultimately, increased adaptation to HT stress. Pharmacological experiments showed that suppressing H2S biosynthesis reduced GSNOR activity, thereby increasing RNS- and ROS-mediated damage to the leaves. Based on these data, we propose that H2S influences the response of woody plants to HT by modulating the NO signal and GSNOR activity.