We investigated the signalling pathways that regulate chloroplast transcription in response to environmental signals. One mechanism controlling plastid transcription involves nuclear-encoded sigma subunits of plastid-encoded plastid RNA polymerase. Transcripts encoding the sigma factor SIG5 are regulated by light and the circadian clock. However, the extent to which a chloroplast target of SIG5...

A set of nuclear mutants of C. reinhardtii were identified that specifically lack translation of the chloroplast-encoded psbA mRNA, which encodes the photosystem II reaction center polypeptide D1. Two of these mutants are deficient in the 47-kD member (RB47) of the psbA RNA-binding complex, which has previously been identified both genetically and biochemically as a putative translational activ...

Assembly of the PSI (photosystem I) complex in eukaryotic photosynthetic organisms depends on the concerted interactions of the nuclear and chloroplast genetic systems. We have identified several nucleus-encoded factors of Chlamydomonas reinhardtii that are specifically required for the synthesis of the two large chloroplast-encoded reaction-centre polypeptides, PsaA and PsaB, of photosystem I ...

Chloroplast genomes in land plants contain approximately 100 genes, the majority of which reside in polycistronic transcription units derived from cyanobacterial operons. The expression of chloroplast genes is integrated into developmental programs underlying the differentiation of photosynthetic cells from non-photosynthetic progenitors. In C4 plants, the partitioning of photosynthesis between...

Genetic analysis has revealed that the accumulation of several chloroplast mRNAs of the green alga Chlamydomonas reinhardtii requires specific nucleus-encoded functions. To gain insight into this process, we have cloned the nuclear gene encoding the Mbb1 factor by genomic rescue of a mutant specifically deficient in the accumulation of the mRNAs of the psbB/psbT/psbH chloroplast transcription u...

The chloroplast is a pivotal organelle in plant cells and eukaryotic algae to carry out photosynthesis, which provides the primary source of the world's food. The expression of foreign genes in chloroplasts offers several advantages over their expression in the nucleus: high-level expression, transgene stacking in operons and a lack of epigenetic interference allowing stable transgene expressio...

Photosynthetic eukaryotes encode two copies of the CSP41 (Chloroplast Stemloop binding Protein of 41 kDa) protein that are of cyanobacterial origin. In Arabidopsis thaliana, the two CSP41 proteins belong to the group of mostabundant chloroplast proteins. Multiple functions have been described for CSP41 proteins, including roles in chloroplast rRNA metabolism and transcription. CSP41a and CSP41b...

Biogenesis of chloroplasts in higher plants is initiated from proplastids, and involves a series of processes by which a plastid able to perform photosynthesis, to synthesize amino acids, lipids, and phytohormones is formed. All plastid protein complexes are composed of subunits encoded by the nucleus and chloroplast genomes, which require a coordinated gene expression to produce the correct co...

Turnip yellow mosaic virus (TYMV) is a positive-strand RNA virus infecting plants. The TYMV 140K replication protein is a key organizer of viral replication complex (VRC) assembly, being responsible for recruitment of the viral polymerase and for targeting the VRCs to the chloroplast envelope where viral replication takes place. However, the structural requirements determining the subcellular l...

Plant chloroplasts contain transcription factors that functionally resemble bacterial sigma factors. We have cloned the full-length cDNA from mustard (Sinapis alba) for a 53 kDa derived polypeptide that contains similarity to regions 1.2-4.2 of sigma70-type factors. The amino acid sequence at the N-terminus has characteristics of a chloroplast transit peptide. An in vitro synthesized polypeptid...