Assembly and comparative analysis of complete mitochondrial genome sequence of an economic plant <i>Salix suchowensis</i>

Abstract

Willow is a widely used dioecious woody plant of <i>Salicaceae</i> family in China. Due to their high biomass yields, willows are promising sources for bioenergy crops. In this study, we assembled the complete mitochondrial (mt) genome sequence of <i>S. suchowensis</i> with the length of 644,437 bp using Roche-454 GS FLX Titanium sequencing technologies. Base composition of the <i>S. suchowensis</i> mt genome is A (27.43%), T (27.59%), C (22.34%), and G (22.64%), which shows a prevalent GC content with that of other angiosperms. This long circular mt genome encodes 58 unique genes (32 protein-coding genes, 23 tRNA genes and 3 rRNA genes), and 9 of the 32 protein-coding genes contain 17 introns. Through the phylogenetic analysis of 35 species based on 23 protein-coding genes, it is supported that <i>Salix</i> as a sister to <i>Populus</i>. With the detailed phylogenetic information and the identification of phylogenetic position, some ribosomal protein genes and succinate dehydrogenase genes are found usually lost during evolution. As a native shrub willow species, this worthwhile research of <i>S. suchowensis</i> mt genome will provide more desirable information for better understanding the genomic breeding and missing pieces of sex determination evolution in the future.