The Defensive Role of Endogenous H2S in Brassica rapa against Mercury-Selenium Combined Stress.

Plants are always exposed to the environment, polluted by multiple trace elements. Hydrogen sulfide (H2S), an endogenous gaseous transmitter in plant cells, can help plant combat single elements with excess concentration. Until now, little has been known about the regulatory role of H2S in response to combined stress of multiple elements. Here we found that combined exposure of mercury (Hg) and selenium (Se) triggered endogenous H2S signal in the roots of Brasscia rapa. However, neither Hg nor Se alone worked on it. In roots upon Hg + Se exposure, the defensive role of endogenous H2S was associated to the decrease in reactive oxygen species (ROS) level, followed by alleviating cell death and recovering root growth. Such findings extend our knowledge of plant H2S in response to multiple stress conditions.