Baba K, Schmidt J, Ruiz AE, Villarejo A, Shiina T, Gardestrom P, Sane AP, Bhalerao RP
Organellar gene transcription and early seedling development are affected in the rpoT,2 mutant of Arabidopsis
Plant J: 2004 38:38-48
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.
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