Methyl jasmonate‐dependent hydrogen sulfide mediates melatonin‐induced aphid resistance of watermelon

Abstract

Abstract As one of the most destructive pests, aphids cause significant damage on various agricultural and horticultural crops. Recently, melatonin has been shown to enhance plant resistance to aphids; however, the underlying mechanisms remain unclear. In this study, our results showed that melatonin, MeJA, and H 2 S enhanced aphid resistance of watermelon in a dose‐dependent manner, accompanied by increases in the defense‐related enzyme activities and lignin accumulation. On the plants pretreated with 100 μM melatonin, 100 μM MeJA, and 50 μM NaHS, the numbers of aphids were 86.0%, 59.6%, and 47.9% lower than that on control plants, respectively, after aphid infestation for 7 days. Melatonin application induced MeJA and H 2 S accumulation in response to aphid infestation, while inhibition of MeJA and H 2 S accumulation attenuated or abolished melatonin‐induced defense response and aphid resistance, suggestive of the involvement of MeJA and H 2 S in melatonin‐induced aphid resistance. MeJA also increased H 2 S accumulation, but inhibition of MeJA biosynthesis prevented melatonin‐enhanced H 2 S accumulation, suggesting that MeJA mediates melatonin‐induced H 2 S accumulation. Furthermore, inhibition of H 2 S production attenuated MeJA‐induced defense response and aphid resistance. Taken together, the current study reveals a novel mechanism in which MeJA‐dependent H 2 S signaling is involved in melatonin‐induced defense response and subsequent aphid resistance. The increasing concern to minimize the use of pesticides and to switch onto sustainable and natural control strategies indicates the great exploitation of such a mechanism in combating aphids.