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 with distinct lifestyles. 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.

中文翻译：

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远红光以茉莉酸酯依赖性方式增强番茄叶片中的可溶性糖水平和灰葡萄孢病的发展

缺乏植物色素感光剂的植物叶片中的可溶性糖水平升高。尽管病原体主要以植物提供的糖为食，但尚未考虑到植物色素失活后植物糖水平升高与疾病发展之间的联系。将番茄植株暴露于对照白光LED（WL）或白光和远红LED（WL + FR）的组合灯中，以灭活植物色素信号传导并调节可溶性糖水平。我们还通过添加葡萄糖或抑制番茄小叶中的光合作用来实验性地控制内部糖水平，然后对可溶性生活方式进行不同程度的病原体可溶性糖定量或生物测定。暴露于WL + FR或缺乏植物色素B（phyB1phyB2双突变体）的叶子中可溶性糖（尤其是葡萄糖和果糖）水平提高。茉莉酸生物合成突变体def1还具有升高的可溶性糖水平，其可以通过外源茉莉酸甲酯的应用来挽救。这表明JA信号传导和初级代谢之间的相互作用。番茄叶片中植物色素失活后可溶性糖水平的增加以JA依赖性方式调节。我们的数据强调了初级代谢在FR诱导的番茄易感性中的重要性，当高密度生长时，这可能有助于提高植物的抗性。