Symbiotic origin of eukaryotic nucleus: From cell body to neo-energide

Abstract

Several aspects of the eukaryotic cell suggest that the nucleus is of symbiotic origin. The nucleus forms, via its perinuclear structures, the primary eukaryotic agent known also as the “cell body” or “energide.” New energides are generated only from other energides, as is the case for all other endosymbiotic organelles. Moreover, the energide can use its secretory apparatus to generate de novo the cell periphery apparatus. In contrast, the energide cannot be generated de novo. All this suggests that the energide was the primary symbiont of the eukaryotic cell and enslaved the host cell by stripping it of its DNA. The energide took control over the host cell that provided it with a protective niche. This feature, supported by other relevant data, suggests that the endoplasmic reticulum (ER) is a secondary organelle generated by the outer portion of the nuclear membrane. The ER represents a specialized domain of the outer nuclear envelope, which orchestrates the energide’s secretory and lytic activities via the ER network, Golgi apparatus, autophagy network, and lysosomes. In this way, the energide integrates the eukaryotic cell via ER/organelle/plasma membrane contact sites into a coherent agent of eukaryotic life. In addition, the plasma membrane provides feedback to the energide and renders protection via the plasma membrane-derived endosomal network. Recent new discoveries suggest archaeal origins for both the energide and its host cell.