The most paradigmatic examples of molecular evolution under positive selection involve genes related to the immune system. Recently, different chloroplastic factors have been shown to be important for plant defenses, among them, the α- and β-subunits of the ATP synthase. The β-subunit has been reported to interact with several viral proteins while both proteins have been implicated with sensitivity to tentoxin, a phytotoxin produced by the widespread fungus Alternaria alternata. Given the relation of both protein to virulence factors, we studied whether these proteins are evolving under positive selection. To this end, we used the dN/dS ratio to examine possible sites under positive selection in several Angiosperm clades. After examining 79 plant genera and 1232 species, we found three times more sites under pervasive diversifying selection in the N-terminal region of the β-subunit compared to the α-subunit, supporting previous results which identified this region as responsible for interacting with viral proteins. Moreover, we found the site 83 of β-subunit under positive selection in several plant genera, a site clearly related to the sensitivity to tentoxin according to biochemistry assays, which possibly reflects the selective pressure of the non-host specific tentoxin across various Angiosperm clades.

正选择下分子进化的最典型例子涉及与免疫系统相关的基因。最近，不同的叶绿体因子已被证明对植物防御很重要，其中包括 ATP 合酶的 α- 和 β- 亚基。据报道，β-亚基与几种病毒蛋白质相互作用，而这两种蛋白质都与对 Tentoxin（一种由广泛分布的Alternaria alternata产生的植物毒素）的敏感性有关. 鉴于这两种蛋白质与毒力因子的关系，我们研究了这些蛋白质是否在正选择下进化。为此，我们使用 dN/dS 比率来检查几个被子植物进化枝中正选择下的可能位点。在检查了 79 个植物属和 1232 个物种后，我们发现与 α 亚基相比，β 亚基 N 末端区域中普遍多样化选择的位点多三倍，支持先前的结果，该结果确定该区域负责与病毒相互作用蛋白质。此外，我们在几个植物属中发现了正选择下的 β-亚基的 83 位点，根据生化测定，该位点与对 Tentoxin 的敏感性明显相关，这可能反映了非寄主特异性 Tentoxin 在各种被子植物进化枝中的选择压力.