ABSTRACT
Plant regulatory circuits coordinating nuclear and plastid gene expression have evolved in response to external stimuli. RNA editing is one of such control mechanisms. We determined the Arabidopsis nuclear-encoded homeodomain-containing protein OCP3 is incorporated into the chloroplast, and contributes to control over the extent of ndhB transcript editing. ndhB encodes the B subunit of the chloroplast NADH dehydrogenase-like complex (NDH) involved in cyclic electron flow (CEF) around photosystem I. In ocp3 mutant strains, ndhB editing efficiency decays, CEF is impaired and disease resistance to fungal pathogens substantially enhanced, a process recapitulated in plants defective in editing plastid RNAs encoding NDH complex subunits due to mutations in previously described nuclear-encoded pentatricopeptide-related proteins (i.e. CRR21, CRR2). Furthermore, we observed that following a pathogenic challenge, wild type plants respond with editing inhibition of ndhB transcript. In parallel, rapid destabilization of the plastidial NDH complex is also observed in the plant following perception of a pathogenic cue. Therefore, NDH complex activity and plant immunity appear as interlinked processes.
Subject(s)
Arabidopsis/metabolism , Plant Immunity/physiology , Plastids/metabolism , RNA Editing/physiology , RNA Stability/physiology , RNA, Plant/metabolism , Arabidopsis/genetics , Arabidopsis/immunology , Arabidopsis Proteins/genetics , Arabidopsis Proteins/immunology , Arabidopsis Proteins/metabolism , Homeodomain Proteins/genetics , Homeodomain Proteins/immunology , Homeodomain Proteins/metabolism , Mutation , NADH Dehydrogenase/genetics , NADH Dehydrogenase/immunology , NADH Dehydrogenase/metabolism , Plastids/genetics , Plastids/immunology , RNA, Plant/genetics , RNA, Plant/immunology , Transcription Factors/genetics , Transcription Factors/immunology , Transcription Factors/metabolismABSTRACT
Parasites like malaria and Toxoplasma possess a vestigial plastid homologous to the chloroplasts of plants. The plastid (known as the apicoplast) is non-photosynthetic but retains many hallmarks of its ancestry including a circular genome that it synthesises proteins from and a suite of biosynthetic pathways of cyanobacterial origin. In this review, the discovery of the apicoplast and its integration, function and purpose are explored. New insights into the apicoplast fatty acid biosynthesis pathway and some novel roles of the apicoplast in vaccine development are reviewed.
Subject(s)
Apicomplexa/physiology , Fatty Acids/biosynthesis , Plastids/physiology , Antiprotozoal Agents/pharmacology , Apicomplexa/drug effects , Apicomplexa/immunology , Apicomplexa/metabolism , Immunity , Intracellular Membranes/immunology , Intracellular Membranes/metabolism , Intracellular Membranes/physiology , Microscopy, Electron, Transmission , Plastids/drug effects , Plastids/immunology , Plastids/metabolism , Plastids/ultrastructure , Protein Transport , Protozoan Infections/immunology , Protozoan Infections/parasitology , Protozoan Infections/therapy , SymbiosisABSTRACT
Epstein-Barr virus (EBV) infects nearly 90% of adults worldwide and is the pathogenic source of a broad spectrum of malignancies originating from lymphoid and epithelial cells. Currently, no vaccine has been developed to immunologically inactivate this virus. In infected patients, anti-EBV viral capsid antigen (VCA) immunoglobins represent some of the useful diagnostic markers for carcinoma development. To demonstrate that the EBV VCA antigen can be produced in plants, the plastid genome of tobacco (Nicotiana tabacum cv. SR1) was transformed with a VCA-expressing cassette. The EBV VCA mRNA was actively transcribed in the transplastomic plants and antigen production was detected. This study indicates that plastid transformation could be a promising strategy in EBV VCA antigen production.
