Abstract
The Escherichia coli RNA polymerase (RNAP) α, β, and β′ core subunits are evolutionarily conserved among bacteria and plastids, and the plastid specificity factors form a functional holoenzyme with the E. coli core. To investigate whether the E. coli core subunits may form a functional hybrid enzyme with the plastid core subunits, we replaced the tobacco plastid RNAP α subunit gene (rpoA) with the E. coliα subunit gene by targeted gene insertion. The transplastomic tobacco plants look similar to tobacco rpoA deletion mutants in that they are chlorophyll-deficient and non-photoautotrophic. In addition, they lack transcripts from promoters recognized by the E. coli-like plastid RNA polymerase. These results indicate that evolutionary conservation between the E. coli and plastid RNA polymerase α subunits is insufficient to allow substitution of the tobacco α subunit with its bacterial counterpart. Interestingly, the cyanobacterial α subunits are as different as the E. coliα subunits; and therefore it is unlikely that replacement of the tobacco α subunit with cyanobacterial α subunits would yield a functional enzyme. Replacement of plastid rpoA with the E. coli RNA polymerase α subunit gene represents the first engineering of a plastid operon in higher plants.
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Received: 1 May 2000 / Accepted: 8 June 2000
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Suzuki, J., Maliga, P. Engineering of the rpl23 gene cluster to replace the plastid RNA polymerase α subunit with the Escherichia coli homologue. Curr Genet 38, 218–225 (2000). https://doi.org/10.1007/s002940000141
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DOI: https://doi.org/10.1007/s002940000141