Untangling the role of ethylene beyond fruit development and ripening: A physiological and molecular perspective focused on the Monilinia-peach interaction

It is already well known that ethylene plays a crucial role in peach fruit growth and ripening, by triggering an unset of biochemical and physiological changes that finally make the fruit attractive for consumption. This said, ethylene is not only responsible for fruit ripening but, in conjunction with other hormones, or key compounds (ROS, polyamines, etc.) is involved in the plant response to numerous abiotic stresses (drought, salt and heat tolerance) as well as the plant/fruit response against certain pathogens. Among peaches, one of the most devastating pathogens is the brown rot causing fungus Monilinia spp. that can affect the fruit both on the field or postharvest. Nonetheless scarce information exists regarding the Monilinia-peach interaction from a physiological and molecular perspective. In this sense, recent studies point out to the importance of ethylene during such interaction, which seems to be dependent on the fruit developmental stage and also on the Monilinia species or even the strain's virulence. Why the fruit or the fungus reacts different to distinct Monilinia species or strains and why such reaction depends on the fruit physiological stage is, however, still elusive. Accordingly, this review aims to shed light on the role of ethylene, alone or through a complex cross-talk with other compounds, not only during peach development and ripening but also during the Monilinia-peach interaction. Based on the available literature, it is clear that not only ethylene biosynthesis but ethylene signaling and the activation of ethylene response factors via ROS may play an essential role during this specific host-pathogen interaction.