Complete chloroplast genome sequence of the avocado: gene organization, comparative analysis, and phylogenetic relationships with other Lauraceae

摘要

The complete chloroplast sequence of the avocado (Persea americana Mill.), a popular tropical fruit tree, was determined in this study. The plastome consists of 152 723 bp, with a typical circular structure including inverted repeats (IRs) 40 104 bp in length separated by a large single-copy region (LSC) and a small single-copy region (SSC) of 93 795 bp and 18 824 bp, respectively. Potential mutation sites, including 61 repeats and 679 simple sequence repeats, were accurately located in the avocado plastome. Compared with the plastomes of five other related Lauraceae, 25 highly variable regions and six micro-inversions were identified, and the contraction event of the IR regions was observed. However, the plastomes of Lauraceae are extremely evolutionarily conservative, with only 0.32% sequence divergence, which is surprisingly low for angiosperms. Further phylogenetic analyses were conducted using eight complete plastomes of Lauraceae and seven barcoding sequences from 23 Persea species. These data support a close relationship between the genera Persea and Machilus and suggest that Persea is polyphyletic.