plant sigma factors, chloroplast transcription, DNA-dependent RNA polymerases, plastid transcription kinase, PEP- and NEP-promoters, gene family
Zusammenfsg.
Sigma factors are key regulators of bacterial transcription. In recent years it has become clear that eukaryotic organisms ranging from algae to higher plants also contain sigma factors. Although the plant sigma factors are confined to the plastid compartment, interacting with the major RNA polymerase PEP (plastid-encoded polymerase), they are products of nuclear genes. Despite considerable information on single members of the plant sigma family, a still unresolved question relates to the purpose of having several of these factors. Is there “division of labor” with one principal and several alternative factors, or are all family members equivalent, i.e. functionally redundant? The aim of the review is to present up-to-date information and try to bring together various aspects of this rapidly evolving field.