moving toward more model algae

A major accomplishment presented in the manuscript by Carrasco Flores et al. (2021) is the generation of a transformation system for the green alga Chlamydomonas sp. SAG25.89 (Chlamydomonas sp. CCMP235), which grows in marine habitats and was isolated from the Nantucket Sound (https://nc ma.ebigalow.org/ccmp235). The features of Chlamydomonas sp. SAG25.89 and the exploitation of the newly developed transformation system could position this organism as a strong marine counterpart to the freshwater Chlamydomonas reinhardtii, the reference green alga that has been extensively characterized at the physiological, genetic, cell, and molecular biological and genomics levels. The Chlamydomonadaceae is a diverse family of unicellular green algae that includes over 30 genera and 800 species, with the type genus-species considered Chlamydomonas reinhardtii. Chlamydomonas reinhardtii was first named by Dangeard (1888) and developed as a genetic model organism by Ruth Sager who elucidated uniparental (chloroplast) genetics in this organism (Sager and Ramanis 1973). Chlamydomonas reinhardtii was subsequently used for classic studies of photosynthesis (Levine and Goodenough 1970) and to dissect flagella (cilia) structure and function (Silflow and Lefebvre 2001). Currently, C. reinhardtii represents the most well characterized of the Chlamydomonas species with a high-quality genome sequence (Merchant et al. 2007, Gallaher et al. 2015) and extensive transcriptomics and multiomics information focused on dissecting the responses of this alga to its environment and over the course of the diel cycle (Gonz alez-Ballester et al. 2010, Boyle et al. 2012, Blaby et al. 2015, Zones et al. 2015, Strenkert et al. 2019). Furthermore, a range of resources and different biochemical and molecular technologies have been used to elucidate biological processes in C. reinhardtii (Sasso et al. 2018, Findinier et al. 2019, Li et al. 2019, Salom e and Merchant 2019). The genus Chlamydomonas is globally distributed with representatives in many different habitats. Limited studies of various marine species of Chlamydomonas have been reported. Chlamydomonas euryale isolated from the Yellow Sea in China represents a model for studying fatty acid and polyketide synthesis (Kohli et al. 2016). Chlamydomonas sp. UW0241, which is present in the arctic, can tolerate low temperatures, hypersalinity, extreme shade conditions, and has unique morphological/structural features associated with the organization of the photosynthetic apparatus (Kalra et al. 2020). Another arctic strain, Chlamydomonas KNM0029C, has commercial potential based on its ability to co-produce biodiesel and bioethanol (Kim et al. 2020). Chlamydomonas euryale, Chlamydomonas sp. SAG25.89 and other marine Chlamydomonas species of the Moewusinia clade are very closely related based on 18S and 26S rRNA sequences, but they are distantly related to C. reinhardtii. Chlamydomonas species have also been isolated from coastal subtropical regions; based on genomic analyses, these species appear to have an abundance of sequences encoding proteins involved in sulfur metabolism (Nelson et al. 2019). The depth of the foundational knowledge acquired with the development of C. reinhardtii as a model green algal system (a flagship organism of the Department of Energy), coupled with the scope of attributes associated with the relatively underexplored world of the Chlamydomonadaceae, makes this family of photosynthetic algae an important target for the examination of diverse species coupled with in-depth studies of a variety of biological processes. The work highlighted in the manuscript by Carrasco Flores et al. (2021) involves the marine strain, Chlamydomonas sp. SAG25.89 (Chlamydomonas sp. CCMP235; Fig. 1; Aiyar et al. 2017). These researchers established a draft genome sequence of this marine Chlamydomonas and C. euryale (approximately 114 and 135 Mb, respectively), both of which are being used for comparative analyses among various algal genomes and to help inform experimental studies. Physiological analyses of Chlamydomonas sp. SAG25.89 demonstrated that this alga is strictly photoautotrophic (cannot use acetate as a carbon source), has a broad pH optimum for growth, and requires ammonium as a nitrogen source. It is unable to use nitrate or nitrite as a sole source of nitrogen and is devoid of the genes encoding J. Phycol. 57, 51–53 (2021) © 2020 Phycological Society of America DOI: 10.1111/jpy.13094