Mitochondrial genome analysis in Passiflora

The genus Passiflora comprises approximately 525 species that represent a vast morphologicaldiversity which serves as the basis for taxonomic classification into subgenera and sections.However, genomic studies are still emerging. Some initiatives have been developed to unravel thenuclear and organellar genome structure of some Passiflora species. So far, it can be said thatplastid genomes (cpDNA) are better documented. Nevertheless, there is a lack of information onthe mitochondrial genome (mtDNA), which should allow complementing evolutionary studies onthe genus. Plant mtDNA shows remarkable variability in terms of genome size and structure,attributed to repetitive DNA sequences involved in homologous recombination and intracellulargene transfer (IGT). Regardless, despite its variability plant, mtDNA does not contain a largerepertoire of genes. Instead, it maintains essential genes related to oxidative phosphorylationwhere the electron transport chain occurs. Our research group initially documented the mtDNA ofP. Organensis (subgenus Decaloba). In the present study, a hybrid assembly approach using shortand long reads generated from Illumina and Oxford Nanopore technologies was employed tounravel the mtDNA of three Passiflora species: P. haematostigma (subgenus Astrophea), P. alata,and P. edulis (subgenus Passiflora). Our aim was to produce new genomic resources and generateknowledge that may be useful in evolutionary approaches to the genus. Despite our efforts, wewere unable to capture a single circular molecule representing the master circle. For P.haematostigma, three circular sequences with lengths of 275,820, 162,684, and 110,306 bp wereidentified. In contrast with P. edulis and P. alata, a single sequence with lengths of 737,209 and693,479 bp, were respectively identified. These mtDNA genomes contain a conserved set of 32protein-coding genes and 3 rRNA genes in the three species, accompanied by a variable number oftRNA genes ranging from 25 to 34. Interestingly, plastidial DNA insertion sites were observed inP. organensis and all three Passiflora species, ranging from 3 to 5 %, highlighting the influenceof IGT events on mtDNA size variation. These remarkable results on the structural and functionalarrangement of Astrophea, Passiflora, and Decaloba mtDNAs suggest that further studies shouldbe conducted to understand the possible relationship between the organization of mitochondrialgenomes and the evolutionary patterns of the genus.