Abstract
Organelle (mitochondria and chloroplasts in plants) genomes lost a large number of genes after the endosymbiosis. Approximately 120 genes are retained in land-plant chloroplast genome and they are transcribed by two distinct transcriptional machinery. One is plastid-encoded RNA polymerase (PEP) and the other is nuclear-encoded RNA polymerase (NEP). Sigma factors regulate the transcriptional activity of PEP and its copy number increased during land plant evolution. This process may be related to the increasing complexity of plastid gene expression. Here, we isolated the Mpsig1 mutant from the population of T-DNA tagged mutants in liverwort (Marchantia polymorpha L.) which is considered as an extant representative of the earliest land plants (terrestrial embryophytes). Blue-Native PAGE and immunoblot analysis revealed that MpSIG1 is involved in at least the accumulation of photosystem I complex. Our study provides insights into the process by which sigma factors have been functionally diverged during land plant evolution.
