The Chlamydomonas reinhardtii Organellar Genomes Respond Transcriptionally and Post-Transcriptionally to Abiotic Stimuli

• Published in: The Plant cell 2002-11, Vol.14 (11), p.2681-2706
• Main Authors: Lilly, Jason W., Maul, Jude E., Stern, David B.
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Chlamydomonas reinhardtii - drug effects; Chlamydomonas reinhardtii - genetics; Chloroplast Proton-Translocating ATPases - genetics; Chloroplasts; Conserved Sequence - genetics; Cytochrome b Group - genetics; Cytochrome b6f Complex; Cytochromes - genetics; Cytochromes f; Dactinomycin - pharmacology; Dicarboxylic Acids - pharmacology; DNA, Chloroplast - genetics; DNA-Directed RNA Polymerases - drug effects; DNA-Directed RNA Polymerases - genetics; DNA-Directed RNA Polymerases - metabolism; Gels; Gene Expression Profiling; Genes; Genomes; Genomics Articles; Messenger RNA; Novobiocin - pharmacology; Nutrients; Oligonucleotide Array Sequence Analysis; Organelles - genetics; Organophosphorus Compounds - pharmacology; Phosphates; Phosphates - pharmacology; Photosynthesis; Phylogeny; Plant cells; Plants; Plastids; Protozoan Proteins - genetics; Rifampin - pharmacology; RNA; RNA, Chloroplast - drug effects; Sulfates; Sulfates - pharmacology; Sulfur; Transcription, Genetic - genetics; Ultraviolet radiation
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.005595

The Chlamydomonas reinhardtii plastid and mitochondrial transcriptomes were surveyed for changes in RNA profiles resulting from growth in 12 culture conditions representing 8 abiotic stimuli. Organellar RNA abundance exhibited marked changes during nutrient stress and exposure to UV light, as revealed by both RNA gel blot and DNA microarray analyses. Of particular note were large increases in tufA and clpP transcript abundance during nutrient limitation. Phosphate and sulfur limitation resulted in the most global, yet opposite, effects on organellar RNA abundance, changes that were dissected further using run-on transcription assays. Removal of sulfate from the culture medium, which is known to reduce photosynthesis, resulted in 2-fold to 10-fold decreases in transcription rates, which were reflected in lower RNA abundance. The decrease in transcriptional activity was completely reversible and recovered to twice the control level after sulfate replenishment. Conversely, phosphate limitation resulted in a twofold to threefold increase in RNA abundance that was found to be a post-transcriptional effect, because it could be accounted for by increased RNA stability. This finding is consistent with the known metabolic slowdown under phosphate stress. Additionally, inhibitor studies suggested that unlike those in higher plants, Chlamydomonas chloroplasts lack a nucleus-encoded plastid RNA polymerase. The apparently single type of polymerase could contribute to the rapid and genomewide transcriptional responses observed within the chloroplast.