Phytochromes as regulators of multiple lines of defense against pathogens in fleshy fruits: an integrated analysis of flavonoid and cuticle metabolism

Abstract

The cuticle is of great importance for the adaptation of plants to different environmental conditions. Taking the tomato (Solanum lycopersicum), a fleshy fruit, as an example, the control of cuticle formation is highly relevant both for the physiology of the fruit and from the perspective of acting as a line of defense against pathogenic agents, a factor that has great agronomic importance/ commercial. In addition to the cuticle, studies demonstrate that flavonoids, a group of phenolic compounds of great commercial importance in fleshy fruits, also act directly in the defense of plants against invading organisms, in many cases increasing their resistance, especially against fungi and bacteria. Recently, studies carried out by our research group found that, in tomato fruits, light signaling mediated by phytochromes plays an active role in regulating cuticle formation. Therefore, to complement these findings, this project aims to characterize the possible role of PHYs and elements involved in the signal transduction of these photoreceptors (for example, PIFs and BBXs proteins) in regulating the accumulation of flavonoids in different regions (pericarp and peel) of the fleshy tomato fruit (Solanum lycopersicum) and its impacts on susceptibility to pathogen attack in this organ. To this end, mature fruits from mutant and transgenic plants with changes in the SlPHYB1/B2-SlPIFs-SlBBXs signaling module will be analyzed for their flavonoid profile and subjected to resistance tests against attack by the necrophytic fungus Botrytis cinerea. Furthermore, a second approach will consist of carrying out the same analyzes on fruits of wild plants under two specific conditions of light spectral composition: shadow simulation versus control. The results obtained in this project will be integrated with data characterizing the structure and composition (epicuticular wax and cutin monomer profiles) of the cuticle of ripe fruits of these same genotypes and the same cultivation conditions. These approaches are expected to generate knowledge regarding the interaction between the components of the SlPHYB1/B2-SlPIFs-SlBBXs signaling module on flavonoid metabolism in different regions of the tomato fruit and its consequences for the defenses of this fleshy fruit. Furthermore, by integrating cuticle deposition data obtained using these same genotypes and cultivation conditions, we will be able to evaluate the importance between cuticular thickness and composition versus the quantity and concentration of types of flavonoids deposited in different regions of the fruits.