Complete Mitogenome Sequencing, Annotation, and Phylogeny of Grateloupia turuturu, a Red Alga with Intronic cox1 Gene

Abstract

The mitochondrial genome (mitogenome) is essential for identifying species and tracing genetic variation, gene patterns, and evolutionary studies. Here, the mitogenome of Grateloupia turuturu was sequenced on the Illumina sequencing platform. This circular mitogenome (28,265 bp) contains 49 genes, including three rRNAs, twenty transfer RNAs (tRNAs), and twenty-six protein-coding genes (PCGs). Nucleotide composition indicates biased AT (68.8%) content. A Group II intronic sequence was identified between two exons of the cox1 gene, and this sequence comprises an open reading frame (ORF) that encodes a hypothetical protein. The gene content, annotation, and genetic makeup are identical to those of Halymeniaceae members. The complete mitogenome sequences of the Grateloupia and Polyopes species were used in a phylogenetic analysis, which revealed that these two genera are monophyletic and that G. turuturu and G. elliptica are closely related. This newly constructed mitogenome will help us better understand the general trends in the development of cox1 introns in Halymeniaceae, as well as the evolution of red algal mitogenomes within the Rhodophyta and among diverse algal species.

Complete Mitochondrial Genome and Its Phylogenetic Position in Red Algae Fushitsunagia catenata from South Korea

“…The long intergenic nucleotide region between nad4 and nad5 in F. catenata (Table 2) was similar to the intergenic regions of the previously reported species, G. elliptica, Gelidium coulteri, G. sinicola, Gracilariopsis andersonii, G. turuturu, and Sarcopeltis skottsbergii. In contrast, the other species investigated in this study possessed intronic tRNA genes between nad4 and nad5 (specifically, trnI in Agarophyton chilense, Hydropuntia rangiferina, Rhodomelopsis africana, R. pseudopalmata, and trnH in Gloiopeltis furcate) [6,[26][27][28][29][30]. The lack of trnI in some species may be attributed to the inaccurate annotation of tRNA.…”

“…No intronic PCGs or tRNA were detected in the mitochondrial genome of F. catenata. However, group II intronic cox1 genes have been identified in red algae, such as G. elliptica and G. turuturu, as reported by Patil et al [27,28]. Additionally, intronic tRNA genes have been reported, including the intronic trnI gene in A. chilense (MZ336082), H. rangiferina (MZ336092), R. africana (OP748274), and R. pseudopalmata (KC875852), and the intronic trnH gene in G. furcate (OP612669).…”

“…Most red algal species that have been sequenced have two rRNAs, rnl and rns. However, two species of the Halymeniales order have an additional rRNA called rns5 [27,28]. rRNA has also been detected in other Florideophyceae red algal species.…”

“…However, the phylogeny based on the cox1 gene sequence separated the sister species of the monophyletic clade of Gigartinales (G. furcate, S. skottsbergii) and Rhodymeniales (F. catenata, R. pseudopalmata). The resulting topology was aligned with a phylogenetic tree constructed from multiple genes and the complete mitochondrial genome sequence [27,28,31]. Filloramo and Sanders [4] found that the Rhodymeniales order is monophyletic and divided into two major lineages: Fryeellaceae, which is a sister of Faucheaceae and Lomentariaceae, and Rhodymeniaceae, which is allied to Champiaceae and Hymenocladiaceae.…”