Proliferation of direct repeats near the Oenothera chloroplast DNA origin of replication |
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Authors: | Sears BB; Stoike LL; Chiu WL |
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Institution: | Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, USA. sears@pilot.msu.edu |
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Abstract: | The spacer between the 16S and 23S rRNA genes of the chloroplast DNA has
been implicated as an origin of replication in several species of plants.
In the evening primrose, Oenothera, this site was found to vary greatly in
size, with plastid genomes (plastomes) being readily distinguished. To
determine whether plastome "strength" in transmission could be correlated
with variation at oriB, the 16S rRNA-trnI spacer was sequenced from five
plastomes. The size variation was found to be due to differential
amplification (and deletion) of combinations of sequences belonging to
seven families of direct repeats. From these comparisons, one short series
of direct repeats and one region capable of forming a hairpin structure
were identified as candidates for the factor that could be responsible for
the differences between strong and weak plastome types. Ample sequence
variation allowed phylogenetic inferences to be made about the
relationships among the plastomes. Phylogenetic trees also could be
constructed for most of the families of direct repeats. The amplifications
and deletions of repeats that account for the size variation at oriB are
proposed to have occurred through extensive replication slippage at this
site.
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