Importance of hydrogen sulfide as the molecular basis of heterosis in hybrid Brassica napus: A case study in salinity response

Heterosis or hybrid vigor is a phenomenon that a heterozygote is superior to two parental lines in one or more traits, or even responses against stresses. However, related molecular mechanism is still not fully elucidated. In this paper, we investigated whether hydrogen sulfide (H2S), a universal signaling molecule in both mammals and plants, participates in heterosis. When upon salinity stress, two parents of Brassica napus (NJ4375 and MB1894) were more sensitive to salinity compared to the hybrid (F1, NJ4375xMB1894), evaluated by the improving effects on the reduction in shoot length, root length, fresh weight of root parts, and chlorophyll content. It was further observed that the increased endogenous H2S synthesis was more pronounced in the hybrid than those of two parental lines when stressed with salinity, suggesting the important roles of endogenous H2S. The removal of endogenous H2S by its biosynthesis inhibitor (PAG) and scavenger (HT) could differentially abolish the salinity tolerance observed in the hybrid. Subsequent experiments showed that the hybrid could maintain ion homeostasis by regulating the sodium and potassium transporters, which was confirmed by modulating NHX1, SOS2, AKT1 and HAK5 transcripts. Proline content was also significantly increased and lipid peroxidation was obviously alleviated in the hybrid plants compared to those in both NJ4375 and MB1894. Above responses in hybrid were sensitive to the inhibition of endogenous H2S synthesis or its scavenging. Overall, our results clearly provided the evidence that salt-tolerant heterosis of hybrid might be closely associated with endogenous H2S signaling.