Transcriptome analysis reveals regulatory networks underlying differential susceptibility to Botrytis cinerea in response to nitrogen availability in Solanum lycopersicum.. Solanum lycopersicum

Transcriptomic analysis in response to Botrytis cinerea infections under conrasting nitrate regime Nitrogen (N) is one of the main limiting nutrients for plant growth and crop yield. It is well documented that changes in nitrate availability, the main N source found in agricultural soils, influences a myriad of developmental programs and processes including the plant defense response. Indeed, many agronomical reports indicate that the plant N nutritional status influences their ability to respond effectively when challenged by different pathogens. However, the molecular mechanisms involved in N-modulation of plant susceptibility to pathogens are poorly characterized. In this work, we show that Solanum lycopersicum defense response to the necrotrophic fungus Botrytis cinerea is affected by plant N availability, with higher susceptibility in nitrate-limiting conditions. Global gene expression responses of tomato against B. cinerea under contrasting nitrate conditions reveals that plant primary metabolism is affected by the fungal infection regardless of N regimes. This result suggests that differential susceptibility to pathogen attack under contrasting N conditions is not only explained by a metabolic alteration. We used a systems biology approach to identify the transcriptional regulatory network implicated in plant response to the fungus infection under contrasting nitrate conditions. Interestingly, hub genes in this network are known key transcription factors involved in ethylene and jasmonic acid signaling. This result positions these hormones as key integrators of nitrate and defense against B. cinerea in tomato plants. Our results provide insights into potential crosstalk mechanisms between necrotrophic defense response and N status in plants. Overall design: To better understand the molecular changes underlying the impact of nitrate availability on plant susceptibility to B. cinerea, we performed plant transcriptome profiling assays on mock-treated (3 biological replicates) and infected plants ( 3 biological replicates) grown under three N conditions, using GeneChip Tomato Genome Arrays (Affymetrix).

不同硝酸盐水平下灰葡萄孢（Botrytis cinerea）侵染响应的转录组学分析
氮（N）是限制植物生长与作物产量的主要限制性养分之一。已有大量研究证实，作为农业土壤中主要氮源的硝酸盐，其可用性变化会调控众多植物发育程序与生理过程，其中就包括植物防御响应通路。事实上，诸多农学研究均表明，植物的氮营养状况会显著影响其应对不同病原菌侵染时的有效防御能力。然而，氮素调控植物对病原菌易感程度的分子机制仍未得到充分解析。
本研究证实，番茄（Solanum lycopersicum）对死体营养型真菌灰葡萄孢的防御响应受植株氮素可用性的调控，在硝酸盐限制条件下番茄的易感程度更高。对不同硝酸盐水平下番茄响应灰葡萄孢侵染的全基因表达谱分析显示，无论氮素水平如何，真菌侵染均会影响植物的初级代谢过程。该结果表明，不同氮素条件下植株对病原菌侵染的易感程度差异，并非仅能通过代谢改变来解释。
本研究采用系统生物学方法，鉴定出了不同硝酸盐水平下植物响应真菌侵染的转录调控网络。有趣的是，该网络中的枢纽基因（hub gene）均为已知的参与乙烯与茉莉酸信号通路的关键转录因子。该结果表明，这两类激素是番茄植株中硝酸盐信号与灰葡萄孢防御响应之间的关键整合因子。本研究结果为解析植物死体营养型防御响应与氮素营养状态之间的潜在串扰机制提供了新的研究视角。
实验整体设计：
为阐明硝酸盐可用性调控植物对灰葡萄孢易感程度的潜在分子变化，本研究针对三种氮素条件下培养的Mock处理组植株（3次生物学重复）与侵染组植株（3次生物学重复），采用Affymetrix番茄全基因组基因芯片（GeneChip Tomato Genome Arrays）开展了转录组表达谱分析。