Abstract Background and Aims The main soluble sugars are important components of plant defence against pathogens, but the underlying mechanisms are unclear. Upon infection by Botrytis cinerea, the activation of several sugar transporters, from both plant and fungus, illustrates the struggle for carbon resources. In sink tissues, the metabolic use of the sugars mobilized in the synthesis of defence compounds or antifungal barriers is not fully understood. Methods In this study, the nitrogen-dependent variation of tomato stem susceptibility to B. cinerea was used to examine, before and throughout the course of infection, the transcriptional activity of enzymes involved in sugar metabolism. Under different nitrate nutrition regimes, the expression of genes that encode the enzymes of sugar metabolism (invertases, sucrose synthases, hexokinases, fructokinases and phosphofructokinases) was determined and sugar contents were measured before inoculation and in asymptomatic tissues surrounding the lesions after inoculation. Key Results At high nitrogen availability, decreased susceptibility was associated with the overexpression of several genes 2 d after inoculation: sucrose synthases Sl-SUS1 and Sl-SUS3, cell wall invertases Sl-LIN5 to Sl-LIN9 and some fructokinase and phosphofructokinase genes. By contrast, increased susceptibility corresponded to the early repression of several genes that encode cell wall invertase and sucrose synthase. The course of sugar contents was coherent with gene expression. Conclusions The activation of specific genes that encode sucrose synthase is required for enhanced defence. Since the overexpression of fructokinase is also associated with reduced susceptibility, it can be hypothesized that supplementary sucrose cleavage by sucrose synthases is dedicated to the production of cell wall components from UDP-glucose, or to the additional implication of fructose in the synthesis of antimicrobial compounds, or both.

中文翻译：

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番茄茎对灰葡萄孢的 N 依赖性易感性中糖代谢基因的调控

摘要 背景与目的主要可溶性糖是植物抵御病原体的重要组成部分，但其潜在机制尚不清楚。被灰葡萄孢菌感染后，来自植物和真菌的几种糖转运蛋白的激活说明了对碳资源的争夺。在汇组织中，在防御化合物或抗真菌屏障的合成中动员的糖的代谢用途尚不完全清楚。方法在这项研究中，番茄茎对灰霉病的易感性的氮依赖性变异被用来检查感染之前和整个过程中参与糖代谢的酶的转录活性。在不同的硝酸盐营养方案下，编码糖代谢酶（转化酶、蔗糖合酶、己糖激酶、果糖激酶和磷酸果糖激酶）并在接种前和接种后病变周围的无症状组织中测量糖含量。主要结果 在高氮可用性下，易感性降低与接种后 2 天多种基因的过度表达有关：蔗糖合酶 Sl-SUS1 和 Sl-SUS3、细胞壁转化酶 Sl-LIN5 至 Sl-LIN9 以及一些果糖激酶和磷酸果糖激酶基因。相比之下，易感性增加对应于编码细胞壁转化酶和蔗糖合酶的几个基因的早期抑制。糖含量的变化过程与基因表达相一致。结论 编码蔗糖合酶的特定基因的激活是增强防御所必需的。