Organellar gene transcription and early seedling development are affected in the rpoT;2 mutant of Arabidopsis.

• An Arabidopsis mutant that exhibited reduced root length was isolated from a population of activation-tagged T-DNA insertion lines in a screen for aberrant root growth. This mutant also exhibited reduced hypocotyl length as well as a delay in greening and altered leaf shape. Molecular genetic analysis of the mutant indicated a single T-DNA insertion in the gene RpoT;2 encoding a homolog of the phage-type RNA polymerase (RNAP), that is targeted to both mitochondria and plastids. A second T-DNA-tagged allele also showed a similar phenotype. The mutation in RpoT;2 affected the light-induced accumulation of several plastid mRNAs and proteins and resulted in a lower photosynthetic efficiency. In contrast to the alterations in the plastid gene expression, no major effect of the rpoT;2 mutation on the accumulation of examined mitochondrial gene transcripts and proteins was observed. The rpoT;2 mutant exhibited tissue-specific alterations in the transcript levels of two other organelle-directed nuclear-encoded RNAPs, RpoT;1 and RpoT;3. This suggests the existence of cross-talk between the regulatory pathways of the three RNAPs through organelle to nucleus communication. These data provide an important information on a role of RpoT;2 in plastid gene expression and early plant development.

Nyckelord

Arabidopsis/*genetics/*growth & development/metabolism

Arabidopsis Proteins/metabolism

Base Sequence

DNA Transposable Elements/genetics

DNA; Bacterial/genetics

DNA; Plant/genetics

DNA-Directed RNA Polymerases/genetics

Gene Expression Regulation; Developmental

Gene Expression Regulation; Plant

Genes; Plant

Mitochondria/genetics

Mutagenesis; Insertional

Mutation

Organelles/genetics

Photosystem II Protein Complex/metabolism

Plastids/genetics

Seedling/growth & development

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