Extracellular Vesicles: A Novel Messenger of Unicellular Microalgae Communication?

Abstract Background Extracellular vesicles (EVs) are nanoparticles with membrane structures secreted by cells that play a role in the transfer of proteins, lipids, small RNAs, lncRNAs and DNA. Thus, EVs mediate mammalian cell-to-cell communication and have potential applications in the diagnosis and treatment of diseases. However, these studies have been primarily focused on the microenvironmental fluids between mammalian cells. Microalgae are single-celled organisms living in natural and dynamic aquatic environments. Whether microalgae can secrete EVs and adapt to changing environments via EV-mediated communication between cells is still unclear. ResultsWe demonstrated that EVs are widely present in microalgae and have surprisingly rich contents of miRNAs and proteins. The differential expression of miRNAs and proteins was correlated with different cell growth stages and abiotic stressors. Our preliminary data suggested that Chlamydomonas EVs significantly affected the growth of the cyanobacterium Synechocystis in full BG11 medium. However, incubating EVs isolated from Chlamydomonas with Synechocystis cells showed that EVs themselves did not promote cell growth in nitrogen depleted BG11 medium. In this case, EVs appear to function primarily via information sensing and message delivery between cells under nutrient stress conditions. More detailed studies need to be conducted to revise our current perspective on the distribution of nutrients in aquatic environments and how EVs may affect microbial communications and interactions.Conculsions These findings suggest that EVs may play a critically important role in information exchange between microalgal cells and, in turn, adaptation to changing aquatic environments.