Not Only Systemin: Prosystemin Harbors Other Active Regions Able to Protect Tomato Plants

Prosystemin is a 200-amino acid precursor expressed in Solanaceae plants whichreleases at the C-terminal part a peptidic hormone called Systemin in response towounding and herbivore attack. We recently showed that Prosystemin is not only a merescaffold of Systemin but, even when deprived of Systemin, is biologically active. Theseresults, combined with recent discoveries that Prosystemin is an intrinsically disorderedprotein containing disordered regions within its sequence, prompted us to investigatethe N-terminal portions of the precursor, which contribute to the greatest disorderwithin the sequence. To this aim, PS1-70 and PS1-120 were designed, produced,and structurally and functionally characterized. Both the fragments, which maintainedtheir intrinsic disorder, were able to induce defense-related genes and to protect tomatoplants against Botrytis cinerea and Spodoptera littoralis larvae. Intriguingly, the biologicalactivity of each of the two N-terminal fragments and of Systemin is similar but notquite the same and does not show any toxicity on experimental non-targets considered.These regions account for different anti-stress activities conferred to tomato plants bytheir overexpression. The two N-terminal fragments identified in this study may representnew promising tools for sustainable crop protection.