The genome of a subterrestrial nematode reveals adaptations to heat

• Published in: Nature communications Vol. 10; no. 1; pp. 5268 - 14
• Main Authors: Weinstein, Deborah J., Allen, Sarah E., Lau, Maggie C. Y., Erasmus, Mariana, Asalone, Kathryn C., Walters-Conte, Kathryn, Deikus, Gintaras, Sebra, Robert, Borgonie, Gaetan, van Heerden, Esta, Onstott, Tullis C., Bracht, John R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21-11-2019; Nature Publishing Group; Nature Portfolio
• Subjects: 45/23; 45/91; 631/181/2474; 631/208/212/2019; 631/208/212/2304; Adaptation; Adaptation, Physiological - genetics; Animals; Aquifers; Biosphere; Divergence; Ecosystem; Fungi; Gene Expression Regulation; Gene Ontology; Gene transfer; Gene Transfer, Horizontal; Genes; Genome, Helminth - genetics; Genomes; Heat shock proteins; Heat stress; Heat tolerance; Heat-Shock Response; Helminth Proteins - genetics; Horizontal transfer; HSP70 Heat-Shock Proteins - genetics; Hsp70 protein; Humanities and Social Sciences; multidisciplinary; Nematoda - classification; Nematoda - genetics; Nematodes; Phylogeny; Positive selection; Prokaryotes; Science; Science (multidisciplinary); Soil - parasitology; Stress, Physiological; Transcription; Transcriptome
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-13245-8

The nematode
Halicephalobus mephisto
was originally discovered inhabiting a deep terrestrial aquifer 1.3 km underground.
H. mephisto
can thrive under conditions of abiotic stress including heat and minimal oxygen, where it feeds on a community of both chemolithotrophic and heterotrophic prokaryotes in an unusual ecosystem isolated from the surface biosphere. Here we report the comprehensive genome and transcriptome of this organism, identifying a signature of adaptation: an expanded repertoire of 70 kilodalton heat-shock proteins (Hsp70) and avrRpt2 induced gene 1 (AIG1) proteins. The expanded Hsp70 genes are transcriptionally induced upon growth under heat stress, and we find that positive selection is detectable in several members of this family. We further show that AIG1 may have been acquired by horizontal gene transfer (HGT) from a rhizobial fungus. Over one-third of the genes of
H. mephisto
are novel, highlighting the divergence of this nematode from other sequenced organisms. This work sheds light on the genomic basis of heat tolerance in a complete subterrestrial eukaryotic genome.
The nematode
Halicephalobus mephisto
has been found more than 1 km underground and can tolerate high heat and low oxygen. Here Weinstein et al. report the genome and transcriptome of
H. mephisto
and identify genomic innovations that likely are responsible for its tolerance to heat.