PDU Espacio de Biología Vegetal del Noreste, Centro Universitario de Tacuarembó (CUT), UdelaR, Ruta 5 km 386,200, 45000, Tacuarembó, Uruguay.
J Mol Evol. 2020 Nov;88(8-9):703-713. doi: 10.1007/s00239-020-09968-8. Epub 2020 Oct 8.
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.
正选择下分子进化最典型的例子涉及与免疫系统相关的基因。最近，不同的质体因子被证明对植物防御很重要，其中包括 ATP 合酶的α-和β-亚基。β-亚基已被报道与几种病毒蛋白相互作用，而这两种蛋白都与 tentoxin 的敏感性有关，tentoxin 是一种由广泛存在的 Alternaria alternata 真菌产生的植物毒素。鉴于这两种蛋白与毒力因子的关系，我们研究了这些蛋白是否在正选择下进化。为此，我们使用 dN/dS 比值来检查几个被子植物类群中可能存在正选择的位点。在检查了 79 个属和 1232 个种后，我们发现β-亚基 N 端区域的普遍分化选择位点是α-亚基的三倍，这支持了先前的结果，即该区域负责与病毒蛋白相互作用。此外，我们在几个植物属中发现β-亚基的 83 位位点受到正选择，根据生物化学测定，该位点与 tentoxin 的敏感性明显相关，这可能反映了非专性寄主 tentoxin 在各种被子植物类群中的选择压力。
