AUTHOR=Cho Hyeon Shik , Lee JunMo 

TITLE=Taxonomic reinvestigation of the genus Tetradesmus (Scenedesmaceae; Sphaeropleales) based on morphological characteristics and chloroplast genomes

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1303175

DOI=10.3389/fpls.2024.1303175

ISSN=1664-462X

ABSTRACT=<p>The genus <italic>Tetradesmus</italic> (Scenedesmaceae; Sphaeropleales) comprises one of the most abundant green algae in freshwater environments. It includes morphologically diverse species that exhibit bundle-like, plane-arranged coenobia, and unicells, because several different <italic>Scenedesmus</italic>-like groups were integrated into this genus based on phylogenetic analysis. Nevertheless, there is no clear information regarding the phylogenetic relationship of <italic>Tetradesmus</italic> species, determined using several marker genes, because of low phylogenetic support and insufficient molecular data. Currently, genome information is available from diverse taxa, which could provide high-resolution evolutionary relationships. In particular, phylogenetic studies using chloroplast genomes demonstrated the potential to establish high-resolution phylogenetic relationships. However, only three chloroplast genomes are available from the genus <italic>Tetradesmus</italic>. In this study, we newly generated 9 chloroplast genomes from <italic>Tetradesmus</italic> and constructed a high-resolution phylogeny using a concatenated alignment of 69 chloroplast protein sequences. We also report one novel species (<italic>T</italic>. <italic>lancea</italic>), one novel variety (<italic>T</italic>. <italic>obliquus</italic> var. <italic>spiraformis</italic>), and two novel formae (<italic>T</italic>. <italic>dissociatus</italic> f. <italic>oviformis</italic>, <italic>T</italic>. <italic>obliquus</italic> f. <italic>rectilineare</italic>) within the genus <italic>Tetradesmus</italic> based on morphological characteristics (e.g., cellular arrangements and coenobial types) and genomic features (e.g., different exon–intron structures in chloroplast genomes). Moreover, we taxonomically reinvestigated the genus <italic>Tetradesmus</italic> based on these results. Altogether, our study can provide a comprehensive understanding of the taxonomic approaches for investigating this genus.</p>