Abstract
Polyamines (PAs) are ubiquitous small aliphatic polycations important for growth, development, and environmental stress responses in plants. Here, we demonstrate that exogenous application of spermine (Spm) and spermidine (Spd) induced cell death at high concentrations, but primed resistance against the necrotrophic fungus Botrytis cinerea in Arabidopsis. At low concentrations, Spm was more effective than Spd. Treatments with higher exogenous Spd and Spm concentrations resulted in a biphasic endogenous PA accumulation. Exogenous Spm induced the accumulation of H2O2 after treatment but also after infection with B. cinerea. Both Spm and Spd induced the activities of catalase, ascorbate peroxidase, and guaiacol peroxidase after treatment but also after infection with B. cinerea. The soluble sugars glucose, fructose, and sucrose accumulated after treatment with high concentrations of PAs, whereas only Spm induced sugar accumulation after infection. Total and active nitrate reductase (NR) activities were inhibited by Spm treatment, whereas Spd inhibited active NR at low concentrations but promoted active NR at high concentrations. Finally, γaminobutyric acid accumulated after treatment and infection in plants treated with high concentrations of Spm. Phenylalanine and asparagine also accumulated after infection in plants treated with a high concentration of Spm. Our data illustrate that Spm and Spd are effective in priming resistance against B. cinerea, opening the door for the development of sustainable alternatives for chemical pesticides.
Highlights
Polyamines (PAs) are small aliphatic polycations that are found in all eukaryotes.In plants, the major PAs include the diamine putrescine (Put), the triamine spermidine (Spd), and the tetraamine spermine (Spm)
We looked at the role of exogenous PAs on endogenous PA contents, sugar and amino acid levels, reactive oxygen species (ROS) dynamics, and ROS scavenging enzymes after treatment and infection
Statistical signifiof PAs, or plants infiltrated with PAs showed more severe lesion development when chalcance was determined by one-way ANOVA and Dunnett’s multiple comparisons test and lenged with necrotrophic pathogens [17,20]
Summary
The major PAs include the diamine putrescine (Put), the triamine spermidine (Spd), and the tetraamine spermine (Spm). They occur in free and conjugated forms as their positive charge allow them to interact with polyanionic molecules such as phospholipids, proteins, and nucleic acids. PAs have diverse functions in several physiological and developmental responses such as cell division, embryogenesis, and senescence [1,2,3]. The regulation of PA metabolism, conjugation, and localization are important to maintain cellular homeostasis. PAs play important physiological roles during (a)biotic stress responses and biotic/abiotic stress cross-tolerance in plants [4,5,6]. PA biosynthesis and degradation are highly regulated by environmental stimuli [7]
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