Could proteins that cause peach allergies also help peaches defend themselves?

Details

PR-10 proteins are a family of allergenic, pathogenesis-related (PR) proteins with multiple functions. The major peach (Prunus persica) allergen Pru p 1.01 and its isoform Pru p 1.06D were found to be highly expressed in fruit skin at the pit-hardening stage, when fruits temporarily lose their susceptibility to the fungal pathogen Monilinia spp.

To investigate whether these two Pru p 1 isoforms might contribute to plant defense, the researchers conducted a laboratory study: they expressed the recombinant proteins in Escherichia coli and purified them. Light scattering experiments and circular dichroism spectroscopy showed that both proteins are monomers in solution and have secondary structures typical of PR-10 proteins.

Neither protein displayed direct antimicrobial activity, but both acted as RNases—enzymes that degrade RNA—a function possibly related to defense. Their RNase activities differed, and only the activity of Pru p 1.01 was affected by the presence of the cytokinin zeatin. This suggests a physiological connection between ligand binding and enzymatic activity in Pru p 1.01.

The researchers evaluated zeatin binding to Pru p 1.01 using isothermal titration calorimetry, obtaining information about the interaction's stoichiometry and thermodynamic parameters. They also used homology modeling to obtain structural models of Pru p 1.01 and Pru p 1.06D and evaluated differences in their binding pockets. These differences might account for the observed difference in binding activity. The proposed links to defense and between binding and enzyme activity remain possibilities, rather than established mechanisms.