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

Authors

  • Kyoko Baba,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden,
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    • These authors contributed equally to this work.

  • Julien Schmidt,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden,
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    • These authors contributed equally to this work.

  • Ana Espinosa-Ruiz,

    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden,
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    • Present address: Centro Nacional de Biotecnología-CSIC, Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.

    • These authors contributed equally to this work.

  • Arsenio Villarejo,

    1. Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umeå, Sweden,
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  • Takashi Shiina,

    1. Faculty of Human and Environment, Kyoto Prefectural University, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan, and
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  • Per Gardeström,

    1. Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umeå, Sweden,
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  • Aniruddha P. Sane,

    1. Plant Gene Expression Laboratory, National Botanical Research Institute, Lucknow-226001, India
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  • Rishikesh P. Bhalerao

    Corresponding author
    1. Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden,
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For correspondence (fax +46 90 7865901; e-mail Rishi.Bhalerao@genfys.slu.se).

Summary

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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