Complete organellar genomes and molecular phylogeny of Hypnea cervicornis (Gigartinales, Florideophyceae) from China

Hypnea cervicornis J. Agardh (Gigartinales, Florideophyceae) is a commercially important carrageenan producing seaweed. Currently, there are no organellar genomes of Hypnea species available in public databases. Here, we report the complete organellar genomes of H. cervicornis using next-generation sequencing technology. The mitochondrial genome has a circular mapping organization with a total length of 25,060 bp and consists of 50 genes (24 protein-coding, 2 rRNA, and 24 tRNA). The plastid genome is also a circular molecule and is 176,446 bp in length and includes 230 genes (194 protein-coding, 3 rRNA, 30 tRNA, 1 tmRNA and 2 misc_RNA). Colinear analysis show that the organellar genomes in the Gigartinales are conserved, except for the inversion of two genes ( trn Y and trn R) in the mitochondrial genome and a 12.5-kb rearrangement in the plastid genome. One stem-loop structure at the intergenic regions between trn S2 and trn A, plus one short hairpin structure between cob and trn L2 are detected in the mitochondrial genome of H. cervicornis . The Ka/Ks analysis reveal that values for most of the protein-coding genes in organellar genomes of H. cervicornis are below one, reflecting the importance of those genes. Phylogenetic relationships based on shared protein-coding genes from the organellar genomes of Rhodophyta are also examined.