Conservation and Tandem Duplication of tRNA Genes in Plant Species

As an evolutionary ancient molecule, transfer RNA (tRNA) is ubiquitous across all domains of life as a living fossil.

Despite substantial research on tRNA genes in various kingdoms, a comprehensive analysis of their conservation and the status of tandem duplication events throughout the tree of plant species studied has yet to be conducted.

The tRNA genes from 50 plant species were identified, and gene length, intron length, and GC content were characterized. Then, identical, tandemly duplicated tRNA genes were analyzed according to the sequence identity and phylogenetic tree.

In this study, a total of 28,262 tRNA genes were identified across 50 plant species, encompassing eight divisions within the plant kingdom. tRNA gene length ranged from 62 to 98 bp and its abundance was found to have no correlation with genome size. The intron-containing tRNA genes are ubiquitously presented in all 50 plant species studied, and the most abundant were tRNA^Met_CAT and tRNA^Tyr_GTC. A total of 578 identical tandemly duplicated tRNA gene pairs were identified and grouped into 410 clusters with 26 tRNA genes to the upmost. Different types of tandem duplication were identified as well, e.g., double-, triple-, and quintuple-tRNA genes, which were repeated for varied times. Tandemly located tRNA gene pairs with anticodons to proline were found to be widely spread in 33 plant species, including both lower and higher plants.

The tRNA genes in different plants are highly conserved in terms of gene length, intron length, GC content, and sequence identity, with especially strong evidence for the strong sequence and structural conservation of tRNA genes, and the tandem duplication is an important driving for the tRNA gene evolution across diverse plant species.