Chloroplast genome-based baraminology of the order Myrtales

Previous plant molecular baraminology studies included analysis of the chloroplast genome alone (Liliales), as well as comparison to hybridization data (Cucurbitaceae). The present study includes the analysis of chloroplast genomes and mitochondrial genomes in various species myrtles (Myrtales).

Myrtales is an economically important order of rosids comprising nine families, 380 genera, and approximately 13,000 species. Compared to other angiosperms with a single phloem layer, Myrtales possesses phloem tissue on both sides of its xylem vessels, making it an apobaramin.

The chloroplast genomes of 298 Myrtales and six Cucurbita species were downloaded from NCBI and aligned using the MAFFT sequence alignment software. Using ward.D2 clustering, 16 statistically significant clusters were found (p<0.05), with at least three species (Melastoma, Syzygium, Corymbia, Allomorphia, Phyllagathis, Lagerstroemia, Eucalyptus, Sonneratia, Sonerila, Trapa, Circaea+Ludwigia, Chamaenerion, Epilobium, Oenothera, and four mixed groups). Oenothera curtiflora, lindheimeri, and villaricae contained a genomic inversion encompassing the genes rbcL, atpB, atpE, rps4, psaA–D, petN, rpoB, ropC1, rpoC2, rps2, atpI, atpH, atpF, atpA, psbI, and psbK. This inversion may have led to the formation of this three-member monobaramin.

The cytochrome-c oxidase subunit I (COI) gene sequence was extracted for 18 Myrtales species having mitochondrial genomes, with Brassica napus as an outlier. These sequences were aligned and clustered. Four statistically significant clusters were identified, including the genera Oenothera (O. biennis, elata and villaricae), Eucalyptus, Sonneratia, and Melastoma. These four genera were also found by the chloroplast analysis, meaning that with two separate lines of evidence, these may indeed be real plant holobaramins.