Ectopic expression of a truncated NLR from wild Arachis enhances resistance against Fusarium oxysporum

Fusarium oxysporum is the causative agent of vascular wilt diseases in dozens of crop species, leading to severe yield losses. The F. o. f.sp. conglutinans Arabidopsis thaliana model system enables the identification of meaningful genotype-phenotype correlations and was applied in this study to evaluate the effects of overexpressing a NLR gene (AsTIR19) from Arachis stenosperma against the pathogen infection. AsTIR19-OE plants exhibited enhanced resistance against F. oxysporum without showing any phenotype penalties. To better comprehend the mechanisms underlying this tolerance, we compared the whole transcriptome sequences of AsTIR19-OE line and wild-type (WT) plants before and after challenge with the pathogen using Illumina HiSeq4000. Through comparison of AsTIR19-OE and WT plants, we identified 778 DEGs resulting from transgene expression, while fungal infection led to 534 DEGs in the OE line. DEGs between the OE line and WT plants were annotated into GO categories, with the most enriched annotations in stress response, oxidoreductase, and cell membrane categories. Meanwhile, plant defense, secreted, and oxidoreductase were the most prevalent categories between infected AsTIR-OE plants and controls. KEGG annotations revealed genes involved in secondary metabolites and phenylpropanoid biosynthesis to be upregulated in OE plants compared to WT, with the MAPK signaling pathway specifically enriched in OE plants after fungal infection. This comprehensive transcriptomic analysis revealed that AsTIR19 overexpression reprogrammed transcriptional networks in transgenic plants, thereby altering the expression of stress-responsive genes across different metabolic pathways. These findings provide valuable insights into the molecular mechanisms underlying the role of this NLR gene under stress conditions.

尖孢镰刀菌（Fusarium oxysporum）是数十种作物维管束萎蔫病的致病菌，可引发严重的产量损失。本研究采用尖孢镰刀菌粘团专化型（Fusarium oxysporum f. sp. conglutinans）-拟南芥（Arabidopsis thaliana）模式系统，以解析有意义的基因型-表型关联，旨在评估过表达狭叶花生（Arachis stenosperma）来源的核苷酸结合富亮氨酸重复受体（NLR）基因AsTIR19对该病原菌侵染的防控效果。AsTIR19过表达（AsTIR19-OE）植株对尖孢镰刀菌的抗性显著增强，且未表现出任何不良表型代价。为深入解析该耐受特性的分子机制，本研究利用Illumina HiSeq4000测序平台，对比分析了病原菌接种前后AsTIR19-OE株系与野生型（WT）植株的全转录组序列。通过对比AsTIR19-OE与野生型植株，本研究鉴定出778个由转基因表达引发的差异表达基因（Differentially Expressed Genes, DEGs），而病原菌侵染在过表达株系中诱导产生了534个差异表达基因。对过表达株系与野生型植株间的差异表达基因进行基因本体（Gene Ontology, GO）注释，结果显示富集最显著的类别为应激响应、氧化还原酶及细胞膜相关功能类群。与此同时，在接种病原菌的AsTIR19-OE植株与对照组之间，植物防御、分泌蛋白及氧化还原酶为占比最高的注释类别。京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）注释结果表明，相较于野生型植株，过表达株系中参与次生代谢产物合成与苯丙烷生物合成的基因呈上调表达；而丝裂原活化蛋白激酶（Mitogen-Activated Protein Kinase, MAPK）信号通路仅在病原菌侵染后的过表达株系中显著富集。本综合转录组分析揭示，AsTIR19过表达重塑了转基因植株的转录调控网络，进而改变了不同代谢通路中应激响应基因的表达模式。上述研究结果为该NLR基因在胁迫条件下的功能分子机制提供了重要的理论参考与见解。