Sodium Hydrosulfide Induces Resistance Against in Apples by Regulating Hydrogen Peroxide and Nitric Oxide Activation of Phenylpropanoid Metabolism.

As a multifunctional signaling molecule, hydrogen sulfide (HS) has been reported to induce plant responses to a variety of abiotic stresses. However, there are no reports on HS treatment inducing resistance in apples against , a biotic factor, and its possible mechanism of action. In this study, fumigating apples with 5 mM sodium hydrosulfide (NaHS), the exogenous donor of HS, for 12 h reduced the diameter of lesions in fruit colonized by . NaHS treatment markedly promoted the synthesis of endogenous HS, hydrogen peroxide (HO), and nitrogen oxide (NO). NaHS treatment enhanced the activities of phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, -coumarate:coenzyme A ligase isoenzymes, caffeoyl-CoA-O-methyltransferase, caffeic acid-O-methyltransferase, ferulic acid-5-hydroxylase, cinnamyl-CoA reductase, and cinnamyl-alcohol dehydrogenase. The treatment also facilitated the production of specific phenolic acids, such as cinnamic acid, -coumaric acid, caffeic acid, ferulic acid, and sinapic acid; total phenolic compounds; coumaryl alcohol; coniferyl alcohol; sinapyl alcohol; and lignin. NaHS treatment induced resistance against in apples through HO- and NO-mediated activation of phenylpropanoid metabolism.