AUTHOR=Liu Feng , Melton James T. III , Lopez-Bautista Juan M. , Chen Nansheng 

TITLE=Multiple Intraspecific Variations of Mitochondrial Genomes in the Green-Tide Forming Alga, Ulva compressa Linnaeus (Ulvophyceae, Chlorophyta)

JOURNAL=Frontiers in Marine Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2020.00714

DOI=10.3389/fmars.2020.00714

ISSN=2296-7745

ABSTRACT=<p>To gain further insights into intraspecific evolution of <italic>Ulva</italic> mitochondrial genomes, the mitogenomes of three morphotypes of the green-tide forming alga, <italic>Ulva compressa</italic> Linnaeus from China and United States, were sequenced and compared with the available data from Ulvophyceae. The <italic>U. compressa</italic> mitogenomes displayed substantial genome size variation at intraspecific level ranging from 61,700 to &gt; 66,587 bp, due to different acquisitions of foreign DNA fragments, gain or loss of both group I and II introns, and non-coding intergenic spacer regions. The <italic>U. compressa</italic> mitogenomes harbored variable gene content ranging from 69 genes (including <italic>orf</italic>s) in <italic>Uco1</italic> to 76 in <italic>Uco5</italic>, and contained different intron content from 4 introns in <italic>Uco3</italic> and <italic>Uco4</italic> to 7 in <italic>Uco1</italic>. A total of 63 genes and only two group IB introns (intron <italic>cox1</italic>-1107 and <italic>cox1</italic>-1125) were shared by these five mitogenomes. The <italic>U. compressa</italic> mitogenomes accumulated many more inverted repeat (IR) elements, ranging from 45 in <italic>Uco1</italic> to 88 in <italic>Uco2</italic>, than that of the other <italic>Ulva</italic> species (3–34). A locally collinear block of eight genes (<italic>rps11-rps19-rps4-rpl16-trnR-trnQ-trnE-trnS</italic>) with the size of 3,631 bp has been inverted only in <italic>Uco1</italic> indicating that the rearrangement event happened after its divergence from <italic>Uco2–5</italic> and might be related to a specific IR element. The majority of the common genes (~76%) displayed high identity (&gt;98%) among these five mitogenomes, while some low values were observed in six genes mainly due to duplication and insertion/deletion mutations of small DNA fragments. Our study presented the first case of multiple intraspecific variations in ulvophycean mitogenomes, and indicated that the mitogenome will be a valuable tool for understanding the native or non-indigenous nature of the cosmopolitan <italic>Ulva</italic> species.</p>