Draft whole-genome and mitochondrial genome assemblies of Steinernema tarimense and Heterorhabditis sp. XJ-55.

Abstract

Entomopathogenic nematodes (EPNs) from the genera Steinernema and Heterorhabditis are potent biocontrol agents. They kill insects through a unique symbiosis with pathogenic bacteria (Xenorhabdus or Photorhabdus), making them ideal for integrated pest management due to their broad host range and environmental safety. Despite high species diversity, genomic resources for these nematodes remain limited. The aim of this study was to characterise the nuclear and mitochondrial genomes of a newly described species, S. tarimense, and a putative novel Heterorhabditis species (strain XJ-55), both obtained from Xinjiang, China. A comprehensive genomic annotation and analysis were conducted to investigate the evolutionary origins of insect parasitism and the molecular adaptation mechanisms involved in host-parasite interactions. Through Illumina sequencing and de novo assembly, we obtained fragmented yet biologically informative genomes for both species. The assembly of S. tarimense reached a BUSCO completeness of 84.06% with an estimated genome size of 84.27 Mb, while that of Heterorhabditis sp. XJ-55 achieved 92.28% completeness with an estimated size of 75.11 Mb. Functional annotation revealed conserved metabolic profiles between the two species, with the Metabolism category being the most abundant. Mitochondrial genomes were successfully reconstructed using MitoZ and NOVOPlasty, resulting in a complete mitogenome of S. tarimense (13,836 bp) and a partial mitogenome of Heterorhabditis sp. XJ-55 (16,865 bp). Comparative mitogenomic analysis highlighted characteristic features such as pronounced A+T bias and distinct codon usage patterns, providing new evolutionary insights into these genera. These genomic resources establish a foundation for future comparative studies and functional investigations, with promising implications for enhancing the biological control efficacy of EPNs in sustainable agricultural systems.