Characteristics of the mitochondrial genome of the invasive plant Tagetes minuta (Asteraceae) on the Qinghai-Tibet Plateau and its evolutionary significance

This study presents the first high-quality assembly and systematic analysis of the complete mitochondrial genome in the invasive plant Tagetes minuta L. The multichromosomal structure spans 268,016 bp across four independent chromosomes (chr1: 91,422 bp; chr2: 76,491 bp; chr3: 52,805 bp; chr4: 47,298 bp), exhibiting characteristic plant mitogenomic AT-biased composition (44.80% GC content). Annotation revealed 56 genes, including 32 PCGs, 21 tRNAs, 3 rRNAs, and 4 pseudogenes. The genome harbors abundant repetitive sequences (97 SSRs, 21 tandem repeats, and 106 dispersed repeats), with the longest forward repeat extending to 1,420 bp. RNA editing analysis identified 570 C→U editing sites across 30 PCGs, significantly enhancing protein hydrophobicity (47.54% of sites shifted to hydrophobic residues). Ka/Ks and Pi analyses demonstrate strong purifying selection on most loci, while atp4, ccmC, and rps4 exhibit signatures of positive selection. Furthermore, 14 homologous fragments were identified between the mitochondrial and chloroplast genomes, collectively spanning 13,795 bp and representing 5.14% of the mitogenome and encompassing 10 intact plastid-derived genes. Phylogenomic evidence confirms that T. minuta forms a monophyletic clade with other Tagetes species. These findings collectively reveal that mitogenomic adaptations—including pre-adaptation traits, structural reorganizations, RNA editing optimization, and inter-organellar gene transfers-likely underpin the species’ robust ecological adaptability on the Qinghai-Tibet Plateau, providing key molecular foundations for deciphering the high-altitude invasion mechanisms of alien plants.