The Essential Role of H2S-ABA Crosstalk in Maize Thermotolerance through the ROS-Scavenging System

Hydrogen sulfide (H₂S) and abscisic acid (ABA), as a signaling molecule and stress hormone, their crosstalk-induced thermotolerance in maize seedlings and its underlying mechanism were elusive. In this paper, H₂S and ABA crosstalk as well as the underlying mechanism of crosstalk-induced thermotolerance in maize seedlings were investigated. The data show that endogenous levels of H₂S and ABA in maize seedlings could be mutually induced by regulating their metabolic enzyme activity and gene expression under non-heat stress (non-HS) and HS conditions. Furthermore, H₂S and ABA alone or in combination significantly increase thermotolerance in maize seedlings by improving the survival rate (SR) and mitigating biomembrane damage. Similarly, the activity of the reactive oxygen species (ROS)-scavenging system, including enzymatic antioxidants catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and superoxide dismutase (SOD), as well as the non-enzymatic antioxidants reduced ascorbic acid (AsA), carotenoids (CAR), flavone (FLA), and total phenols (TP), was enhanced by H₂S and ABA alone or in combination in maize seedlings. Conversely, the ROS level (mainly hydrogen peroxide and superoxide radical) was weakened by H₂S and ABA alone or in combination in maize seedlings under non-HS and HS conditions. These data imply that the ROS-scavenging system played an essential role in H₂S-ABA crosstalk-induced thermotolerance in maize seedlings.