The chloroplast genome of a resilient chlorophycean microalga Asterarcys sp

Asterarcys is a resilient microalgal species which can sustain high light intensities and have high biomass and lipid productivity under mixotrophy. These attributes make it a potential candidate to produce biodiesel and biofuels. However, no genetic information is currently available for this species. Here, we report the chloroplast genome sequence of Asterarcys sp. and compare it with the chloroplast genome of closely related chlorophyceaen microalgae. The chloroplast genome of Asterarcys sp. is present as a ~111 kb circular molecule with 88 genes and a coding density of 50.28%. The 111,776 bp genome shows a quadripartite structure with two 6297 bp long inverted repeats separating single copy regions (SSC) of almost equal sizes. The small and compact genome of Asterarcys shows similarity in gene structure and organization with that of its closest relative Scenedesmus obliquus. It reinforces the compact nature of chloroplast genomes of Sphaeropleales as compared to that of inflated genomes in Chlamydomonadales. The genome shows a biased distribution of genes with 50 of the protein-coding genes encoded from one strand and 15 from the opposite strand. This biased distribution of genes is likewise to that of Scenedesmus obliquus. The phylogenetic tree based on protein-coding genes from chlorophycean species places Asterarcys close to Scenedesmus. The chloroplast genome information of Asterarcys will help understand the phylogeny of Sphaeropleales and Chlorophyceae. In the present study, we also report a simple and effective method for isolation of Asterarcys sp. chloroplast DNA of high quality and purity which is an essential prerequisite for efficient genome sequencing.