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A horizontally transferred tRNA Cys gene in the sugar beet mitochondrial genome: evidence that the gene is present in diverse angiosperms and its transcript is aminoacylated
Author(s) -
Kitazaki Kazuyoshi,
Kubo Tomohiko,
Kagami Hiroyo,
Matsumoto Takuma,
Fujita Asami,
Matsuhira Hiroaki,
Matsunaga Muneyuki,
Mikami Tetsuo
Publication year - 2011
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2011.04684.x
Subject(s) - biology , gene , genetics , transfer rna , genome , sugar beet , mitochondrion , mitochondrial dna , nuclear gene , rna , horticulture
Summary Of the two tRNA Cys (GCA) genes, trnC1‐ GCA and trnC2‐ GCA, previously identified in mitochondrial genome of sugar beet, the former is a native gene and probably a pseudo‐copy, whereas the latter, of unknown origin, is transcribed into a tRNA [tRNA Cys2 (GCA)]. In this study, the trnC2 ‐GCA sequence was mined from various public databases. To evaluate whether or not the trnC2 ‐GCA sequence is located in the mitochondrial genome, the relative copy number of its sequence to nuclear gene was assessed in a number of angiosperm species, using a quantitative real‐time PCR assay. The trnC2 ‐GCA sequence was found to exist sporadically in the mitochondrial genomes of a wide range of angiosperms. The mitochondrial tRNA Cys2 (GCA) species from sugar beet ( Beta vulgaris ), spinach ( Spinacea oleracea ) and cucumber ( Cucumis sativus ) were found to be aminoacylated, indicating that they may participate in translation. We also identified a sugar beet nuclear gene that encodes cysteinyl‐tRNA synthetase, which is dual‐targeted to mitochondria and plastids, and may aminoacylate tRNA Cys2 (GCA). What is of particular interest is that trnC1 ‐GCA and trnC2 ‐GCA co‐exist in the mitochondrial genomes of eight diverse angiosperms, including spinach, and that the spinach tRNA Cys1 (GCA) is also aminoacylated. Taken together, our observations lead us to surmise that trnC2 ‐GCA may have been horizontally transferred to a common ancestor of eudicots, followed by co‐existence and dual expression of trnC1 ‐GCA and trnC2 ‐GCA in mitochondria with occasional loss or inactivation of either trnC ‐GCA gene during evolution.