Mitochondrial Genome Assemblies of Elysia timida and Elysia cornigera and the Response of Mitochondrion-Associated Metabolism during Starvation

Abstract

Some sacoglossan sea slugs sequester functional plastids (kleptoplasts) from their food, which continue to fix CO2 in a light dependent manner inside the animals. In plants and algae, plastid and mitochondrial metabolism are linked in ways that reach beyond the provision of energy-rich carbon compounds through photosynthesis, but how slug mitochondria respond to starvation or alterations in plastid biochemistry has not been explored. We assembled the mitochondrial genomes of the plastid-sequestering sea slugs Elysia timida and Elysia cornigera from RNA-Seq data that was complemented with standard sequencing of mitochondrial DNA through primer walking. Our data confirm the sister species relationship of the two Sacoglossa and from the analysis of changes in mitochondrial-associated metabolism during starvation we speculate that kleptoplasts might aid in the rerouting or recycling of reducing power independent of, yet maybe improved by, photosynthesis.

Animal biosynthesis of complex polyketides in a photosynthetic partnership

“…In a previous study of E. timida and E. cornigera starvation, it was demonstrated that oxidative stress is extremely high in E. cornigera and its STR chloroplasts during starvation; the slug quickly dies 22,25 . By contrast, in E. timida oxidative stress does not increase upon starvation, and the animals live for extended periods on photosynthesis.…”

“…Good candidate polypropionate synthases were not observed in bacterial metagenomes, suggesting a possible origin in the animals or chloroplasts. We took advantage of recently released genomes and transcriptomes of three sacoglossans 22,[25][26][27] , Elysia chlorotica 26,27 , E. timida 22,25 , and E. cornigera 22,25 , to test this hypothesis. E. chlorotica contains polypropionates ent-9,10deoxytridachione and elysione , while E. timida contains ent-9,10-deoxytridachione and several relatives (Fig.…”

Animal biosynthesis of complex polyketides in a photosynthetic partnership

“…We were unable to identify good candidate polypropionate synthases from the bacterial metagenomes, suggesting a possible origin in the animals or chloroplasts. We took advantage of recently released genomes and transcriptomes of three sacoglossans 11,22–24 , Elysia chlorotica, E. timida , and E. cornigera , to test this hypothesis. E. chlorotica contains polypropionates ent -9,10-deoxytridachione and elysione 25 , while E. timida contains ent -9,10-deoxytridachione and several relatives (Fig.…”

Peer Review #2 of "Accessible molecular phylogenomics at no cost: obtaining 14 new mitogenomes for the ant subfamily Pseudomyrmecinae from public data (v0.1)"

“…Also, previous studies indicate that it is possible to recover complete and/or nearly complete mitochondrial sequences from RNA-Seq data (Tian & Smith, 2016;Rauch et al, 2017;Plese et al, 2018) and targeted sequencing strategies as exome (Picardi & Pesole, 2012;Guo et al 2013;Samuels et al 2013) and UCE (Ultra Conserved Elements) off-target data (Raposo do Amaral et al, 2015;Miller et al 2016). The assembly of numerous complete mitogenomes and/or large mitochondrial contigs from the sequencing of pooled multi-species samples has also been performed successfully (Timmermans et al, 2015;Linard et al, 2018) under an approach named 'mito-metagenomics' (Tang et al, 2014) or 'mitochondrial metagenomics' (MMG) (Crampton-Platt et al, 2015).…”