Far-red light enhances soluble sugar levels and Botrytis cinerea disease development in tomato leaves in a jasmonate-dependent manner
Plants lacking phytochrome photoreceptors display elevated soluble sugar levels in leaves. Although pathogens principally feed on sugars supplied by the plant, the link between increased plant sugar levels upon phytochrome inactivation and disease development has not been considered. Tomato plants were exposed to control white LED (WL) or a combination of white and far-red LED (WL+FR) light, to inactivate phytochrome signaling and modulate soluble sugar levels. We also experimentally manipulated internal sugar levels by either supplementing glucose or inhibiting photosynthesis in tomato leaflets prior to performing soluble sugar quantifications or bioassays with pathogens. Tomato plants exposed to WL+FR or lacking phytochrome B (phyB1phyB2 double mutants) show enhanced levels of soluble sugars, especially glucose and fructose, in their leaves. The jasmonic acid biosynthesis mutant def1 also has elevated soluble sugar levels, which could be rescued by exogenous methyl-jasmonate application. This indicates an interplay between JA signaling and primary metabolism. The increase in soluble sugar levels in tomato leaves upon phytochrome inactivation is regulated in a JA-dependent manner. Our data stress the importance of primary metabolism in the FR-induced susceptibility in tomato that could contribute to promote plant resistance when grown at high density.