Identification of Soybean Proteins and Genes Differentially Regulated in Near Isogenic Lines Differing in Resistance to Aphid Infestation

Soybean aphid is an important pest causing significant yield losses. The Rag2 locus confers resistance to soybean aphid biotypes 1 and 2. Transcriptomic and proteomic analyses were done over a 48 h period after aphid infestation using near isogenic lines (NILs) differing at the Rag2 locus. Comparing the Rag2 and/or rag2 lines identified 3445 proteins, of which 396 were differentially regulated between the two lines, including proteins involved in cell wall metabolism, carbohydrate metabolism, and stress response. RNA-seq transcriptomic analysis identified 2361 genes significantly regulated between the resistant and susceptible lines. Genes upregulated in the Rag2 line were annotated as being involved in cell wall, secondary, and hormone metabolism as well as in stress, signaling, and transcriptional responses. Genes downregulated in the Rag2 line were annotated as being involved in photosynthesis and carbon metabolism. Interestingly, two genes (unknown and mitochondrial protease) located within the defined Rag2 locus were expressed significantly higher in the resistant genotype. The expression of a putative NBS-LRR resistant gene within the Rag2 locus was not different between the two soybean lines, but a second NBL-LRR gene located just at the border of the defined Rag2 locus was. Therefore, this gene may be a candidate R gene controlling aphid resistance.大豆蚜（Soybean aphid）是一类可造成显著产量损失的重要农业害虫。Rag2位点可赋予大豆抵御蚜虫生物型1和2的抗性。本研究采用在Rag2位点存在遗传差异的近等基因系（near isogenic lines，NILs），在蚜虫侵染后的48小时内开展了转录组学与蛋白质组学分析。通过对比携带Rag2与rag2的大豆品系，共鉴定得到3445种蛋白质，其中396种在两个品系间存在差异表达，涵盖细胞壁代谢、碳水化合物代谢及应激响应相关的蛋白。RNA测序（RNA-seq）转录组分析鉴定得到2361个在抗病与感病品系间存在显著表达差异的基因。在Rag2品系中上调表达的基因经注释后可知，其参与细胞壁代谢、次生代谢与激素代谢，同时涉及应激响应、信号转导及转录调控过程；而在Rag2品系中下调表达的基因则主要参与光合作用与碳代谢过程。值得注意的是，定位于已明确界定的Rag2位点内的两个基因（未知功能基因与线粒体蛋白酶基因）在抗病基因型中的表达量显著更高。Rag2位点内一个推定的核苷酸结合位点-富亮氨酸重复（NBS-LRR）抗性基因的表达在两个大豆品系间并无显著差异，但紧邻该Rag2位点边界的另一个NBL-LRR基因则存在明显表达差异。据此推测，该基因或可作为调控蚜虫抗性的候选抗病基因（R gene）。