Diatom plastids depend on nucleotide import from the cytosol

摘要: Diatoms are ecologically important algae that acquired their plastids by secondary endosymbiosis, resulting in a more complex cell structure and an altered distribution of metabolic pathways when compared with organisms primary plastids. Diatom surrounded 4 membranes; the outermost membrane is continuous endoplasmic reticulum. Genome analyses suggest nucleotide biosynthesis is, contrast to higher plants, not located plastid, but cytosol. As consequence, nucleotides have be imported into organelle. However, mechanism entry plastid unknown. We identified high number putative transporters (NTTs) diatoms Thalassiosira pseudonana Phaeodactylum tricornutum characterized first 2 isoforms (NTT1 NTT2). GFP-based localization studies revealed both investigated NTTs targeted membranes, NTT1 most likely enters innermost envelope via stroma. Heterologously expressed acts as proton-dependent adenine importer, whereas NTT2 facilitates counter exchange (deoxy-)nucleoside triphosphates. Therefore, these functionally resemble from obligate intracellular bacteria impaired metabolism rather than ATP/ADP exchanging harbor specifically-adapted transport system key players supply plastid.