Prosystemin N-terminal protein fragments mitigate salt stress damages in tomato plants

Abstract Understanding and exploiting the intrinsic mechanisms of tolerance to multiple stresses in plants is the new frontier of sustainable agriculture, since environmental challenges often occur simultaneously in agricultural systems. We recently identified three fragments, named PS1-70, PS1-120 and G, in the scaffold of prosystemin, the protein precursor of tomato systemin. These protein fragments efficiently protect tomato plants against Botrytis cinerea and Spodoptera littoralis larvae attacks by inducing defence-related genes. Since it was previously demonstrated that prosystemin protects tomato plants also against soil salinity, we analyzed the ability of PS1-70, PS1-120 and G to confer salt tolerance. As expected, the application of 150 mM NaCl induced 24% reduction of shoot fresh weight. The treatment with PS1-70 and G induced 9% and 8% increase of shoot fresh weight. In addition, under salt stress, there is a significant increase in root biomass in treated plants suggesting that the treatment mitigated salt stress. Noteworthy, fragments application improved the growth of shoots, indicating a biostimulant activity on tomato growth. These data correlated with the upregulation of key stress-related genes, (CAT2, APX2, and HSP90), associated with the activation of antioxidant and free radical scavenging reactions in stressed plant cells. Our results add novel tools to the complex problem of sustainable crop protection against different environmental stresses.