Raphidocelis subcapitata (=Pseudokirchneriella subcapitata) provides an insight into genome evolution and environmental adaptations in the Sphaeropleales

Abstract

The Sphaeropleales are a dominant group of green algae, which contain species important to freshwater ecosystems and those that have potential applied usages. In particular, Raphidocelis subcapitata is widely used worldwide for bioassays in toxicological risk assessments. However, there are few comparative genome analyses of the Sphaeropleales. To reveal genome evolution in the Sphaeropleales based on well-resolved phylogenetic relationships, nuclear, mitochondrial, and plastid genomes were sequenced in this study. The plastid genome provides insights into the phylogenetic relationships of R. subcapitata, which is located in the most basal lineage of the four species in the family Selenastraceae. The mitochondrial genome shows dynamic evolutionary histories with intron expansion in the Selenastraceae. The 51.2 Mbp nuclear genome of R. subcapitata, encoding 13,383 protein-coding genes, is more compact than the genome of its closely related oil-rich species, Monoraphidium neglectum (Selenastraceae), Tetradesmus obliquus (Scenedesmaceae), and Chromochloris zofingiensis (Chromochloridaceae); however, the four species share most of their genes. The Sphaeropleales possess a large number of genes for glycerolipid metabolism and sugar assimilation, which suggests that this order is capable of both heterotrophic and mixotrophic lifestyles in nature. Comparison of transporter genes suggests that the Sphaeropleales can adapt to different natural environmental conditions, such as salinity and low metal concentrations.

Regulation of Oxygenic Photosynthesis during Trophic Transitions in the Green Alga Chromochloris zofingiensis

“…C. zofingiensis, which was placed in Chlorella, Muriella, and Mychonastes before its current placement into Chromochloris (Fucikova and Lewis, 2012), is an ;4-mm unicellular, haploid, coccoid alga with a mitochondrial network and a single starch-containing chloroplast (Roth et al, 2017). In contrast to C. reinhardtii, C. zofingiensis can grow with Glc as its sole carbon source, and has an expanded number of hexose transporter genes, suggesting the ability to acclimate to a wide variety of environmental conditions (Suzuki et al, 2018). Under specific conditions such as heterotrophy, nitrogen deprivation, or high light, C. zofingiensis accumulates high amounts of the valuable secondary ketocarotenoid astaxanthin and biofuel precursors (Breuer et al, 2012;Liu et al, 2014;Mulders et al, 2014;Huang et al, 2016;Zhang et al, 2016;Roth et al, 2017).…”

Unveiling of a novel bifunctional photoreceptor, Dualchrome1, isolated from a cosmopolitan green alga

“…Cells were collected by gentle centrifugation. DNA was extracted as described in Suzuki et al 48 . The paired-end library was constructed using a TruSeq DNA PCR-free Kit (lllumina Inc., San Diego, CA, USA), according to the manufacturer's protocol.…”

Review of and Recommendations for Monitoring Contaminants and their Effects in the San Francisco Bay−Delta

“…(Colbourne et al 2005;Orsini et al 2016), Hyalella azteca (Christie et al 2018;Poynton et al 2018), Chironomus spp. (Herrero et al 2017;Mantilla et al 2018) • phytoplankton-e.g., Raphidocelis subcapitata (Suzuki et al 2018) Below, we present a summary of 'Omic tools and data sets available for fish, invertebrates, and algal species associated with the Bay−Delta.…”

“…Numerous phytoplankton species have been used in freshwater and marine algal toxicity tests. One of the ecotoxicological standards for which 'Omic data exists (Suzuki et al 2018) is Raphidocelis subcapitata (= Selenastrum capricornutum; = Pseudokirchneriella subcapitata). Advances in 'Omic technologies, as detailed above, now provide the capacity with which to obtain genomic information from a multitude of species for which there has been no prior genomic data.…”