Table_6_Identification and Characterization of NBS Resistance Genes in Akebia trifoliata.XLSX

Akebia trifoliata is an important multiuse perennial plant that often suffers attacks from various pathogens due to its long growth cycle, seriously affecting its commercial value. The absence of research on the resistance (R) genes of A. trifoliata has greatly limited progress in the breeding of resistant varieties. Genes encoding proteins containing nucleotide binding sites (NBSs) and C-terminal leucine-rich repeats (LRRs), the largest family of plant resistance (R) genes, are vital for plant disease resistance. A comprehensive genome-wide analysis showed that there were only 73 NBS genes in the A. trifoliata genome, including three main subfamilies (50 coiled coil (CC)-NBS-LRR (CNL), 19 Toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) and four resistance to powdery mildew8 (RPW8)-NBS-LRR (RNL) genes). Additionally, 64 mapped NBS candidates were unevenly distributed on 14 chromosomes, most of which were assigned to the chromosome ends; 41 of these genes were located in clusters, and the remaining 23 genes were singletons. Both the CNLs and TNLs were further divided into four subgroups, and the CNLs had fewer exons than the TNLs. Structurally, all eight previously reported conserved motifs were identified in the NBS domains, and both their order and their amino acid sequences exhibited high conservation. Evolutionarily, tandem and dispersed duplications were shown to be the two main forces responsible for NBS expansion, producing 33 and 29 genes, respectively. A transcriptome analysis of three fruit tissues at four developmental stages showed that NBS genes were generally expressed at low levels, while a few of these genes showed relatively high expression during later development in rind tissues. Overall, this research is the first to identify and characterize A. trifoliata NBS genes and is valuable for both the development of new resistant cultivars and the study of molecular mechanisms of resistance.

三叶木通（Akebia trifoliata）是一种重要的多用途多年生植物，由于其生长周期较长，常遭受多种病原菌侵染，严重影响其商业价值。目前针对三叶木通抗病（R）基因的研究匮乏，极大限制了抗病品种的育种进程。编码含核苷酸结合位点（NBS）与C端富亮氨酸重复序列（LRR）的蛋白的基因是植物最大的抗病（R）基因家族，对植物抗病性至关重要。本研究通过全基因组范围的综合分析发现，三叶木通基因组中仅存在73个NBS基因，分为三大亚家族：50个卷曲螺旋-核苷酸结合位点-富亮氨酸重复序列（CC-NBS-LRR, CNL）型、19个Toll/白介素-1受体-核苷酸结合位点-富亮氨酸重复序列（TIR-NBS-LRR, TNL）型以及4个抗白粉病8-核苷酸结合位点-富亮氨酸重复序列（RPW8-NBS-LRR, RNL）型基因。此外，64个已定位的NBS候选基因不均匀分布于14条染色体上，其中大多数定位于染色体末端；41个基因成簇分布，剩余23个则为单个分散基因。CNL与TNL型基因均可进一步分为4个亚组，且CNL型基因的外显子数量少于TNL型。在结构层面，NBS结构域中均包含此前报道的8个保守基序，其基序排列顺序与氨基酸序列均表现出高度保守性。进化分析表明，串联重复与散在重复是驱动NBS基因家族扩张的两大主要动力，分别产生了33个和29个基因。对3个果实组织在4个发育阶段的转录组分析结果显示，NBS基因整体表达水平较低，但其中少数基因在果皮组织发育后期呈现出相对较高的表达量。综上，本研究首次完成了三叶木通NBS基因的鉴定与特征分析，可为抗病新品种培育以及抗病分子机制研究提供重要参考价值。