Deciphering the Multi-Chromosomal Mitochondrial Genome of Populus simonii

Mitochondria, inherited maternally, are energy metabolism organelles that generate most of the chemical energy needed to power cellular various biochemical reactions. Deciphering mitochondrial genome (mitogenome) is important for elucidating vital activities of species. The complete chloroplast (cp) and nuclear genome sequences of ( ) have been reported, but there has been little progress in its mitogenome. Here, we assemble the complete mitogenome into three circular-mapping molecules (lengths 312.5, 283, and 186 kb) with the total length of 781.5 kb. All three molecules of the mitogenome had protein-coding capability. Whole-genome alignment analyses of four species revealed the fission of poplar mitogenome in . Comparative repeat analyses of four mitogenomes showed that there were no repeats longer than 350 bp in mitogenomes, contributing to the stability of genome sizes and gene contents in the genus . As the first reported multi-circular mitogenome in , this study of mitogenome are imperative for better elucidating their biological functions, replication and recombination mechanisms, and their unique evolutionary trajectories in .