Hydrogen peroxide functioned as a redox signaling molecule in the putrescine-promoted drought tolerance in cabernet sauvignon.

• Exogenous putrescine promoted the photosynthesis in grape seedlings under drought stress. • Exogenous putrescine activated VvRBOHb and VvRBOHc2 and stimulated H 2 O 2 synthesis. • Exogenous putrescine activated the endogenous polyamine synthetic pathway. • H 2 O 2 was critical for putrescine-mediated drought resistance in grape seedlings. Drought stress poses a significantly constraint on grape growth, development, and yield. Increasing drought resistance is a critical goal of viticulture, especially in the context of global warming. In this study, exogenous putrescine (Put) significantly improved the photosynthetic and antioxidant capacity of drought-stressed Cabernet Sauvignon seedlings, stimulated the biosynthesis of endogenous polyamines, and reinforced the protective impact on organelle structure. Hydrogen peroxide scavenging agent (DMTU) severely undermined the drought resistance conferred by Put. The elimination of H 2 O 2 using exogenous DMTU led to a dramatic reduction in the Fv/Fm value, antioxidant enzyme activity, and endogenous PAs content in the grape leaves. Our observations suggested that Put increased the expression of the nicotinamide adenine dinucleotide phosphate oxidase genes VvRBOHb and VvRBOHc2 , which stimulated the synthesis of H 2 O 2 in the cells. H 2 O 2 functioned as signal molecules and contributed to the regulatory role of Put in enhancing the drought resistance of Cabernet Sauvignon grape seedlings. [ABSTRACT FROM AUTHOR]