Chloroplast development in Arabidopsis thaliana requires the nuclear-encoded transcription factor Sigma B

Development of plastids into chloroplasts, the organelles of photosynthesis , is triggered by light. However, little is known of the factors involved i n the complex coordination of light-induced plastid gene expression, which must be directed by both nuclear and plastid genomes, We have isolated an A rabidopsis mutant, abc1, with impaired chloroplast development, which resul ts in a pale green leaf phenotype, The mutated nuclear gene encodes a sigma factor, SigB, presumably for the eubacterial-like plastid RNA polymerase, Our results provide direct evidence that a nuclear-derived prokaryotic-like SigB protein, plays a critical role in the coordination of the two genomes for chloroplast development. (C) 2000 Federation of European Biochemical S ocieties. Published by Elsevier Science B.V. All rights reserved.