Assembly and comparative analysis of complete mitochondrial genome sequence of an economic plantSalix suchowensis

Abstract

Willow is a widely used dioecious woody plant ofSalicaceaefamily 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 ofS. suchowensiswith the length of 644,437 bp using Roche-454 GS FLX Titanium sequencing technologies. Base composition of theS. suchowensismt 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 thatSalixas a sister toPopulus. 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 ofS. suchowensismt genome will provide more desirable information for better understanding the genomic breeding and missing pieces of sex determination evolution in the future.