Complete mitochondrial genome assembly and comparative analysis of the endangered species Petrocosmea qinlingensis

Abstract

Petrocosmea qinlingensis W. T. Wang (Gesneriaceae) is an endemic species from the Qinling Mountains of China . This species has a restricted distribution and a small population size and has been designated as a National Grade II Protected Plant in China. It has attracted taxonomic and horticultural interest. Although the chloroplast genome of P. qinlingensis has been reported, its mitochondrial genome has not yet been characterized, which limited comparative analyses of mitochondrial genome organization. In this study, we sequenced and assembled the complete mitochondrial genome of P. qinlingensis. The mitogenome of P. qinlingensis is 373,687 bp in length and consists of three circular chromosomes, with an overall GC content of 44.11%. It encodes 35 protein-coding genes, 24 tRNA genes, three rRNA genes, and one pseudogene. A total of 79 SSRs, eight tandem repeats and 124 dispersed repeats were identified. Thirty-one plastid-derived fragments were detected, accounting for 5.24% of the mitochondrial genome. In addition, 535 C-to-U RNA editing sites were predicted across protein-coding genes. Most mitochondrial genes were inferred to be under purifying selection, while several genes showed elevated Ka/Ks ratios. Comparative synteny analyses revealed extensive structural rearrangements among Lamiales mitogenomes. Phylogenetic analysis based on mitochondrial genome data supported the placement of P. qinlingensis within the Gesneriaceae family. This study reported the mitochondrial genome sequence of P. qinlingensis , providing a genomic resource for future comparative and evolutionary studies within Gesneriaceae.