TY - JOUR T1 - De novo organelle biogenesis in the cyanobacterium TDX16 released from the green alga <em>Haematococcus pluvialis</em> JF - bioRxiv DO - 10.1101/161463 SP - 161463 AU - Qing-lin Dong AU - Xiang-ying Xing AU - Yang Han AU - Xiao-lin Wei AU - Shuo Zhang Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/05/14/161463.abstract N2 - It is believed that eukaryotes arise from prokaryotes, which means that organelles can form in the latter. Such events, however, had not been observed previously. Here, we report the biogenesis of organelles in the endosymbiotic cyanobacterium TDX16 that escaped from its senescent/necrotic host cell of green alga Haematococcus pluvialis. In brief, organelle biogenesis in TDX16 initiated with cytoplasm compartmentalization, followed by de-compartmentalization, DNA allocation, and re-compartmentalization, as such two composite organelles-the primitive chloroplast and primitive nucleus sequestering minor and major fractions of cellular DNA respectively were formed. Thereafter, the eukaryotic cytoplasmic matrix was built up from the matrix extruded from the primitive nucleus; mitochondria were assembled in and segregated from the primitive chloroplast, whereby the primitive nucleus and primitive chloroplast matured into nucleus and chloroplast respectively; while most mitochondria turned into double-membraned vacuoles after matrix degradation. Results of pigment analyses, 16S rRNA and genome sequencing revealed that TDX16 is a phycocyanin-containing cyanobacterium resembling Chroococcidiopsis thermalis, which had acquired 9,017,401bp DNAs with 10301 genes form its host. Therefore, organelle biogenesis in TDX16 was achieved by hybridizing the acquired eukaryotic DNAs with its own ones and expressing the hybrid genome.Organelle biogenesis in TDX16 results in its transition into a new eukaryotic alga TDX16-DE, which provides a reference to re-understand the development, structure, function and association of organelles in eukaryotes and the reasons behind them, and has implications on other sections of biology, particularly cancer biology and evolutionary biology: (1) the formation and maturation of the small organelle-less nascent cancer cells share striking similarities with TDX16 development and transition, so, it is most likely that cancer cells arise from bacteria; (2) organelle biogenesis in TDX16 uncovers a way of new organelle and new single-celled eukaryote formation, and in light of which, the ancestral organelles were likely formed in rather than transformed form the endosymbiotic prokaryotes that had acquired their hosts’ DNAs.AUGAutosporangiumCChloroplastCDChloroplast debrisCECytoplasmic envelopeCFChromatin fibersCGCyanophycin granulesCHEChloroplast envelopeCLMCloudlike materialsCMCytoplasmic membraneCPVCompound vesiclesCRCristaeCVCombined vesiclesCWCell wallCXCarboxysomesDFDNA FibersDGVDense-margined vesiclesDLFDNA-like fibrilsDMFDouble-layered membrane fragmentDMSDouble-layered membrane segmentDMVDouble-membraned vesiclesDRVDilated ring-shaped vesiclesDSVDense vesicleDTDNA threadsDVDotted vesiclesEDElectron-dense debrisEDVElectron-dense vesiclesEFElectron-dense fibrilsEGElectron-dense granulesEISEmpty Inner spaceELElectron-dense layerELMElectron-translucent materialsELVElectron-translucent vesiclesEMEukaryotic cytoplasmic matrixEOBElectron-opaque bodiesEOPElectron-opaque particlesEOMElectron-opaque materialsEOVElectron-opaque vesiclesEPElectron-dense particlesEPMElectron-transparent materialsEREndoplasmic reticulumESExtracytoplasmic spaceEVElectron-transparent vesicleEWEukaryotic cell wallFMFibrillar materialsGAGolgi apparatusGPGlobular particlesHGBHeterogenous globular bodiesIBIntranuclear bodyICEIntracytoplasmic envelopeICPInner cytoplasmIESInter envelope spaceIIMInner intracytoplasmic membraneIISInner intracytoplasmic spaceINSInterspaceISIntracytoplasmic spaceITBInternal bodyIVInternal vesicleIVSInvaginated spaceLDLipid dropletLDBLess electron-dense bodiesLDMLess electron-dense materialsLMLimiting membraneMMitochondrionMEMitochondrial envelopeMFMembrane fragmentsMLMicrofibrilsMLBMultilamellar bodyMRMargin residuesMSMembrane segmentsMTMembranous elementsMVMicrovesiclesNNucleusNENuclear envelopeNICNew inner cytoplasmNISNew inner intracytoplasmic spaceNSNew intracytoplasmic spaceNTNucleoid-like structureNUNucleoidNXNew intracytoplasmic matrixOCPOuter cytoplasmOEOuter nuclear envelopeOGOsmiophilic granulesOIMOuter intracytoplasmic membraneOISOuter intracytoplasmic spaceOPVOpaque-periphery vesicleOMOuter membraneOVOblong vesiclesPPeptidoglycan layerPBPolyphosphate bodiesPCPrimitive chloroplastPCBPhycobilisomesPDPyrenoidsPGPlastoglobuliPLPeptidoglycan-like layerPMTPrimitive thylakoidsPNPrimitive nucleusPNEPrimitive nuclear envelopePOPoresPTPrimary thylakoidsRBRibosomesRMResidual membranesRVRing-shaped vesiclesSASporangiumSGStarch granulesSHSheathSMVSmaller vesiclesSMStromaSOVSmall opaque vesicleSPStarch plateSTSecondary thylakoidsSVSmall vesiclesTThylakoidsTLThylakoid-like structureTMFTwo-layered membrane fragmentTMVThick margin vesicleTVTiny vesiclesVVacuoleVBVesicle-containing body ER -