Nucleotide-binding site (NBS)-type disease resistance genes (R genes) play key roles in plant immune responses and have co-evolved with pathogens over the course of plant lifecycles. Comparative genomic studies tracing the dynamic evolution of NBS-encoding genes have been conducted using many important plant lineages. However, studies on Sapindaceae species have not been performed. In this study, a discrepant number of NBS-encoding genes were identified in the genomes of Xanthoceras sorbifolium (180), Dinnocarpus longan (568), and Acer yangbiense (252). These genes were unevenly distributed and usually clustered as tandem arrays on chromosomes, with few existed as singletons. The phylogenetic analysis revealed that NBS-encoding genes formed three monophyletic clades, RPW8-NBS-LRR (RNL), TIR-NBS-LRR (TNL), and CC-NBS-LRR (CNL), which were distinguished by amino acid motifs. The NBS-encoding genes of the X. sorbifolium, D. longan, and A. yangbiense genomes were derived from 181 ancestral genes (three RNL, 23 TNL, and 155 CNL), which exhibited dynamic and distinct evolutionary patterns due to independent gene duplication/loss events. Specifically, X. sorbifolium exhibited a “first expansion and then contraction” evolutionary pattern, while A. yangbiense and D. longan exhibited a “first expansion followed by contraction and further expansion” evolutionary pattern. However, further expansion in D. longan was stronger than in A. yangbiense after divergence, suggesting that D. longan gained more genes in response to various pathogens. Additionally, the ancient and recent expansion of CNL genes generated the dominance of this subclass in terms of gene numbers, while the low copy number status of RNL genes was attributed to their conserved functions.

核苷酸结合位点（NBS）型抗病基因（[R基因）在植物免疫反应中起关键作用，并在植物生命周期中与病原体共同进化。已经使用许多重要的植物谱系进行了追踪NBS编码基因动态进化的比较基因组研究。但是，尚未对Sapindaceae物种进行研究。在这项研究中，发现了NBS编码基因的差异基因黄单胞菌 （180）， 龙眼 （568），和 宏cer（252）。这些基因分布不均，通常聚集成染色体上的串联阵列，很少以单子形式存在。系统发育分析表明，NBS编码基因形成了三个单系进化枝，RPW8-NBS-LRR（RNL），TIR-NBS-LRR（TNL）和CC-NBS-LRR（CNL），它们通过氨基酸基序进行区分。NBS的编码基因X.山梨醇， 龙眼和 阳bi基因组来自181个祖先基因（三个RNL，23个TNL和155个CNL），由于独立的基因复制/丢失事件，它们表现出动态且独特的进化模式。特别，X.山梨醇 表现出“先膨胀后收缩”的进化模式，而 阳bi 和 龙眼表现出“先扩张，后收缩再扩张”的演化模式。但是，在龙眼 比中强 阳bi 分歧之后，表明 龙眼获得了更多的基因来应对各种病原体。另外，CNL基因的古老和最近扩展在基因数目方面产生了该亚类的优势，而RNL基因的低拷贝数状态则归因于它们的保守功能。