Mitogenome Characteristics and Intracellular Gene Transfer Analysis of Four Adansonia Species

Adansonia L. (1753) belongs to the family Malvaceae and is commonly known as the baobab tree. This species holds significant cultural and ecological value and is often referred to as the 'tree of life.' Although its nuclear genome has been reported, the mitogenome has not yet been studied. Mitogenome research is crucial for understanding the evolution of the entire genome. In this study, we assembled and analyzed the mitogenomes of four Adansonia species by integrating short-read and long-read data. The results showed that the mitogenomes of all four Adansonia species were resolved as single circular sequences. Their total genome lengths ranged from 507,138 to 607,344 bp and contained a large number of repetitive sequences. Despite extensive and complex rearrangements between the mitogenomes of Adansonia and other Malvaceae species, a phylogenetic tree constructed based on protein-coding genes clearly indicated that Adansonia is more closely related to the Bombax. Selection pressure analysis suggests that the rps4 gene in Adansonia may have undergone positive selection compared to other Malvaceae species, indicating that this gene may play a significant role in the evolution of Adansonia. Additionally, by analyzing intracellular gene transfer between the chloroplast, mitochondria, and nuclear genomes, we found that genes from the chloroplast and mitochondria can successfully transfer to each chromosome of the nuclear genome, and the psbJ gene from the chloroplast remains intact in both the mitochondrial and nuclear genomes. This study enriches the genetic information of Adansonia and provides important evidence for evolutionary research in the family Malvaceae.