Delaye Luis, Valadez-Cano Cecilio, Pérez-Zamorano Bernardo
CINVESTAV Irapuato.
Ingeniería Genética, CINVESTAV - Irapuato; Irapuato, Guanajuato, Mexico.
PLoS Curr. 2016 Mar 15;8:ecurrents.tol.e68a099364bb1a1e129a17b4e06b0c6b. doi: 10.1371/currents.tol.e68a099364bb1a1e129a17b4e06b0c6b.
The ancestor of Paulinella chromatophora established a symbiotic relationship with cyanobacteria related to the Prochloroccocus/Synechococcus clade. This event has been described as a second primary endosymbiosis leading to a plastid in the making. Based on the rate of pseudogene disintegration in the endosymbiotic bacteria Buchnera aphidicola, it was suggested that the chromatophore in P. chromatophora has a minimum age of ~60 Myr. Here we revisit this estimation by using a lognormal relaxed molecular clock on the 18S rRNA of P. chromatophora. Our time estimates show that depending on the assumptions made to calibrate the molecular clock, P. chromatophora diverged from heterotrophic Paulinella spp. ~ 90 to 140 Myr ago, thus establishing a maximum date for the origin of the chromatophore.
嗜色裸藻（Paulinella chromatophora）的祖先与属于原绿球藻属/聚球藻属进化枝的蓝细菌建立了共生关系。这一事件被描述为导致正在形成的质体的第二次原发性内共生。基于内共生细菌蚜虫内共生菌（Buchnera aphidicola）中假基因的解体速率，有人提出嗜色裸藻中的色素体的最小年龄约为6亿年。在这里，我们通过对嗜色裸藻的18S rRNA使用对数正态松弛分子钟来重新审视这一估计。我们的时间估计表明，根据校准分子钟所做的假设，嗜色裸藻在约9000万至1.4亿年前从异养的裸藻属物种分化出来，从而确定了色素体起源的最大日期。
