AUTHOR=Li Ruoran , Jia Xuli , Zhang Jing , Jia Shangang , Liu Tao , Qu Jiangyong , Wang Xumin 

TITLE=The Complete Plastid Genomes of Seven Sargassaceae Species and Their Phylogenetic Analysis

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.747036

DOI=10.3389/fpls.2021.747036

ISSN=1664-462X

ABSTRACT=<p>Sargassum is one of the most important genera of the family Sargassaceae in brown algae and is used to produce carrageenan, mannitol, iodine, and other economic substances. Here, seven complete plastid genomes of <italic>Sargassum ilicifolium var. conduplicatum, S. graminifolium, S. phyllocystum, S. muticum, S. feldmannii, S. mcclurei</italic>, and <italic>S. henslowianum</italic> were assembled using next-generation sequencing. The sizes of the seven circular genomes ranged from 124,258 to 124,563 bp, with two inverted regions and the same set of plastid genes, including 139 protein-coding genes (PCGs), 28 transfer (t)RNAs, and 6 ribosomal (r)RNAs. Compared with the other five available plastid genomes of Fucales, 136 PCGs were conserved, with two common ones shared with <italic>Coccophora langsdorfii</italic>, and one with <italic>S. fusiforme</italic> and <italic>S. horneri</italic>. The co-linear analysis identified two inversions of trnC(gca) and trnN(gtt) in ten Sargassum species, against <italic>S. horneri</italic> and <italic>C. langsdorfii</italic>. The phylogenetic analysis based on the plastid genomes of 55 brown algae (Phaeophyceae) showed four clades, whose ancient ancestor lived around 201.42 million years ago (Mya), and the internal evolutionary branches in Fucales started to be formed 92.52 Mya, while Sargassum species were divided into two subclades 14.33 Mya. Our novel plastid genomes provided evidence for the speciation of brown algae and plastid genomic evolution events.</p>