Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, People's Republic of China.
Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
BMC Evol Biol. 2019 Jan 9;19(1):12. doi: 10.1186/s12862-019-1351-1.
Horizontal gene transfer and gene duplication are two major mechanisms contributing to the evolutionary adaptation of organisms. Previously, polygalacturonase genes (PGs) were independently horizontally transferred and underwent multiple duplications in insects (e.g., mirid bugs and beetles). Here, we chose three phytozoophagous mirid bugs (Adelphocoris suturalis, A. fasciaticollis, A. lineolatus) and one zoophytophagous mirid bug (Nesidiocoris tenuis) to detect whether the duplication, molecular evolution, and expression levels of PGs were related to host range expansion in mirid bugs.
By RNA-seq, we reported 30, 20, 19 and 8 PGs in A. suturalis, A. fasciaticollis, A. lineolatus and N. tenuis, respectively. Interestingly, the number of PGs was significantly positive correlation to the number of host plants (P = 0.0339) in mirid bugs. Most PGs (> 17) were highly expressed in the three phytozoophagous mirid bugs, while only one PG was relatively highly expressed in the zoophytophagous mirid bug. Natural selection analysis clearly showed that a significant relaxation of selection pressure acted on the PGs in zoophytophagous mirid bugs (K = 0.546, P = 0.0158) rather than in phytozoophagous mirid bugs (K = 1, P = 0.92), suggesting a function constraint of PGs in phytozoophagous mirid bugs.
Taken together with gene duplication, molecular evolution, and expression levels, our results suggest that PGs are more strictly required by phytozoophagous than by zoophytophagous mirid bugs and that the duplication of PGs is associated with the expansion of host plant ranges in mirid bugs.
水平基因转移和基因复制是导致生物进化适应的两个主要机制。以前，多聚半乳糖醛酸酶基因（PGs）在昆虫中独立地发生水平转移并经历了多次复制（例如盲蝽和甲虫）。在这里，我们选择了三种植食性盲蝽（Adelphocoris suturalis、A. fasciaticollis、A. lineolatus）和一种捕食性盲蝽（Nesidiocoris tenuis）来检测 PG 基因的复制、分子进化和表达水平是否与盲蝽的宿主范围扩张有关。
通过 RNA-seq，我们分别在 A. suturalis、A. fasciaticollis、A. lineolatus 和 N. tenuis 中报道了 30、20、19 和 8 个 PGs。有趣的是，PGs 的数量与盲蝽的宿主植物数量呈显著正相关（P=0.0339）。大多数 PGs（>17）在三种植食性盲蝽中高度表达，而在捕食性盲蝽中只有一个 PG 相对高度表达。自然选择分析清楚地表明，在捕食性盲蝽中，PG 受到的选择压力显著放松（K=0.546，P=0.0158），而不是在植食性盲蝽中（K=1，P=0.92），这表明 PG 在植食性盲蝽中有功能限制。
综合基因复制、分子进化和表达水平，我们的结果表明，PG 在植食性盲蝽中比在捕食性盲蝽中更为严格地需要，并且 PG 的复制与盲蝽宿主植物范围的扩张有关。
