Data_Sheet_1_Root-Knot Nematode Resistance in Gossypium hirsutum Determined by a Constitutive Defense-Response Transcriptional Program Avoiding a Fitness Penalty.zip

Cotton (Gossypium spp.) is the most important renewable source of natural textile fiber and one of the most cultivated crops around the world. Plant-parasitic nematode infestations, such as the southern Root-Knot Nematode (RKN) Meloidogyne incognita, represent a threat to cotton production worldwide. Host-plant resistance is a highly effective strategy to manage RKN; however, the underlying molecular mechanisms of RKN-resistance remain largely unknown. In this study, we harness the differences in RKN-resistance between a susceptible (Acala SJ-2, SJ2), a moderately resistant (Upland Wild Mexico Jack Jones, WMJJ), and a resistant (Acala NemX) cotton entries, to perform genome-wide comparative analysis of the root transcriptional response to M. incognita infection. RNA-seq data suggest that RKN-resistance is determined by a constitutive state of defense transcriptional behavior that prevails in the roots of the NemX cultivar. Gene ontology and protein homology analyses indicate that the root transcriptional landscape in response to RKN-infection is enriched for responses related to jasmonic and salicylic acid, two key phytohormones in plant defense responses. These responses are constitutively activated in NemX and correlate with elevated levels of these two hormones while avoiding a fitness penalty. We show that the expression of cotton genes coding for disease resistance and receptor proteins linked to RKN-resistance and perception in plants, is enhanced in the roots of RKN-resistant NemX. Members of the later gene families, located in the confidence interval of a previously identified QTL associated with RKN resistance, represent promising candidates that might facilitate introduction of RKN-resistance into valuable commercial varieties of cotton. Our study provides novel insights into the molecular mechanisms that underlie RKN resistance in cotton.

棉花（棉属Gossypium spp.）是全球最重要的天然纺织纤维可再生来源，亦是栽培范围最广的作物之一。植物寄生线虫侵染——例如南方根结线虫（Root-Knot Nematode，RKN，学名Meloidogyne incognita）——对全球棉花生产构成严重威胁。寄主植物抗性是防治根结线虫的高效策略，但目前学界对根结线虫抗性的潜在分子机制仍知之甚少。本研究利用三类棉花材料在根结线虫抗性上的差异：感病材料Acala SJ-2（简称SJ2）、中抗材料陆地棉野生墨西哥杰克琼斯（Upland Wild Mexico Jack Jones，简称WMJJ）以及抗病材料Acala NemX，对南方根结线虫（M. incognita）侵染后的根部转录响应开展全基因组比较分析。RNA测序（RNA-seq）数据显示，根结线虫抗性由Acala NemX品种根部固有的防御转录调控状态主导。基因本体（Gene Ontology，GO）与蛋白质同源性分析表明，根结线虫侵染后的根部转录谱中，与茉莉酸、水杨酸这两种植物防御核心激素相关的应答通路显著富集。该类应答在NemX品种中呈组成型激活状态，且与两种激素水平升高相关，同时未造成适合度代价。本研究发现，在抗根结线虫的NemX品种根部，编码与植物根结线虫抗性及识别相关的病害抗性蛋白与受体蛋白的棉花基因表达量显著上调。上述两类基因家族的成员位于此前已定位的根结线虫抗性数量性状位点（Quantitative Trait Locus，QTL）置信区间内，是可用于将根结线虫抗性性状导入优质商业棉花品种的潜在候选基因。本研究为解析棉花根结线虫抗性的分子机制提供了全新视角。