A new gene encoding tRNA(Pro) (GGG) is present in the chloroplast genome of black pine: a compilation of 32 tRNA genes from black pine chloroplasts.

The chloroplast genome of black pine (Pinus thunbergii), a gymnosperm, contains 32 different tRNA genes, 30 of which correspond to those previously identified in tobacco and rice chloroplast genomes. Two additional genes encode tRNA(Pro) (GGG) and tRNA(Arg) (CCG); the former is newly identified while the latter is present in liverwort, Physcomitrella patens and Angiopteris lygodiifolia, chloroplast genomes. Moreover, a partial copy of the split tRNA(Gly) (UCC) gene and full copies of tRNA(His) (GUG), tRNA(Thr) (GGU) and tRNA(Ser) (GCU) genes are present in the large single-copy region of the genome, suggesting extensive rearrangements of the chloroplast genome during evolution. No tRNA genes whose tRNA products can recognize codons CUU/C (Leu) and GCU/C (Ala) have been found. We propose that the 32 tRNAs are sufficient to read all the 61 sense codons in the black pine system using the "two-out-of-three" and the "U:N wobble" mechanisms.