Evolution of the plastid ribosomal RNA operon in a nongreen parasitic plant: Accelerated sequence evolution,altered promoter structure,and tRNA pseudogenes |
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| Authors: | Kenneth H Wolfe Deborah S Katz-Downie Clifford W Morden Jeffrey D Palmer |
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| Institution: | (1) Department of Biology, Indiana University, 47405 Bloomington, IN, USA;(2) Present address: Department of Genetics, University of Dublin, Trinity College, Dublin 2, Ireland;(3) Present address: Department of Plant Biology, University of Illinois, 61801 Urbana, IL, USA;(4) Present address: Department of Botany, University of Hawaii, 96822 Honolulu, HI, USA;(5) Department of E.E.C.B., University of Hawaii, 96822 Honolulu, HI, USA |
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| Abstract: | The nucleotide sequence of a 7.4 kb region containing the entire plastid ribosomal RNA operon of the nongreen parasitic plant Epifagus virginiana has been determined. Analysis of the sequence indicates that all four rRNA genes are intact and almost certainly functional. In contrast, the split genes for tRNAIle and tRNAAla present in the 16S-23S rRNA spacer region have become pseudogenes, and deletion upstream of the 16S rRNA gene has removed a tRNAVal gene and most of the promoter region for the rRNA operon. The rate of nucleotide substitution in 16S and 23S rRNAs is several times higher in Epifagus than in tobacco, a related photosynthetic plant. Possible reasons for this, including relaxed translational constraints, are discussed. |
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| Keywords: | molecular evolution plastid DNA promoter pseudogene ribosomal RNA gene transfer RNA gene |
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