It is the intracellular association between two cells. It can be defined as the symbiotic relationship in which one symbiont inhabits in the cytoplasm of another. Homologous and heterologous are the two types of cytoplasm. If both the cells are derived from the same taxon or same biont (like e.g. synergides in the makrogametophyte of seed plants, it is called as homologous and if partner cells comes from the different taxa, then it is termed as heterologous. This special symbiotic association has the facultative ability to an evolutionary change of a dibiont-system into a new monobiont-system bearing a new cell organelle, the exogenosome. The best examples for this illustration are chloroplasts and mitochondria which are widely believed to be evolved from bacteria that once lived as endosymbionts within the cytoplasm of ancestors of eukaryotic cells. endosymbiosis is accomplished by the concomitant transfer of endosymbionts genes to the host nucleus, by a process known as Endosymbiotic Gene Transfer (EGT) and is believed to be vital to cement the interdependence of two symbionts which is accompanied by the import of the nuclear ï¿½encoded plastid proteins back to the original compartment through a protein ï¿½import apparatus. The process of EGT is relatively straightforward as it can be recapitulated in the laboratory.
Last date updated on July, 2014