A nucleus-encoded dynamin-like protein controls endosymbiont division in the trypanosomatid <i>Angomonas deanei</i>.

Abstract

<i>Angomonas deanei</i> is a trypanosomatid of the Strigomonadinae. All members of this subfamily contain a single β-proteobacterial endosymbiont. Intriguingly, cell cycles of host and endosymbiont are synchronized. The molecular mechanisms underlying this notable level of integration are unknown. Previously, we identified a nucleus-encoded dynamin-like protein, called ETP9, that localizes at the endosymbiont division site of <i>A. deanei</i>. Here, we found by comparative genomics that endosymbionts throughout the Strigomonadinae lost the capacity to autonomously form a division septum. We describe the cell cycle-dependent subcellular localization of ETP9 that follows accumulation of the bacterium-encoded division protein FtsZ at the endosymbiont division site. Furthermore, we found that ETP9 is essential in symbiotic but dispensable in aposymbiotic <i>A. deanei</i> that lost the endosymbiont. In the symbiotic strain, ETP9 knockdowns resulted in filamentous, division-impaired endosymbionts. Our work unveiled that in <i>A. deanei</i> an endosymbiont division machinery of dual genetic origin evolved in which a neo-functionalized host protein compensates for losses of endosymbiont division genes.