Response of Energy Reserves in Entomopathogenic Nematodes to Drought-Stress and Expression Analysis of Energy Metabolism-Related Genes in Arid Areas

TL;DR

This study explores how entomopathogenic nematodes respond to drought stress by analyzing their energy reserves and gene expression to improve their use in arid pest control.

Contribution

The study identifies energy reserve dynamics and gene expression patterns in drought-resistant nematodes under low humidity.

Findings

Lipids are the main energy reserve in entomopathogenic nematodes under low humidity stress.

Drought-resistant nematodes show increased protein, lipid, and trehalose levels under stress.

Transcriptome analysis reveals gene pathways involved in energy metabolism adaptation to drought.

Abstract

Entomopathogenic nematodes (EPNs) (genera: Steinernema, Heterorhabditis, and Oscheius), which kill insect hosts with the aid of symbiotic bacteria, are used widely as biocontrol agents in agricultural pest control because of their advantages of active search for pests, wide host range, and safety to humans, livestock, and the environment. In particular, they have good control effects on boring pests and soil pests. As a novel type of biological agent, the energy reserve capacity and low-humidity adaptability of EPNs in the natural environment are directly linked to their pest control efficiency. In this study, we measured energy reserves, biological traits, and behavioral characteristics of two EPN species under low humidity conditions, and performed transcriptome analysis on drought-resistant strains. This approach offers a new perspective for elucidating the mechanisms of drought resistance in EPNs.

The free-living infective juveniles of entomopathogenic nematodes (EPNs) are critical biological control agents against insect pests. The field efficacy of EPNs is largely determined by their tolerance to low-humidity stress, a trait closely linked to the mobilization of their energy reserves. This study aims to investigate how varying levels of humidity stress influence energy reserve dynamics in two EPNs, Steinernema kraussei 0657L and Heterorhabditis brevicaudis 0641TY, and their relationship with the survival rate and pathogenicity. The results demonstrated that lipids were the predominant energy reserve, followed by proteins and sugars. Notably, neutral lipid constituted approximately 3% of the total lipid content. Among sugars, soluble sugar levels were the highest, followed by glycogen and trehalose. Exposure to low-humidity stress resulted in increased levels of protein, total lipid, glycogen, and trehalose in nematodes. These increases were more pronounced in S. kraussei 0657L, a highly drought-resistant strain, compared to H. brevicaudis 0641TY. Furthermore, the accumulation of protein, total lipid, and trehalose was negatively correlated with survival rate and pathogenicity. However, positive correlations were observed between trehalose and both total lipids and soluble sugars. Furthermore, transcriptome analysis revealed that under low-humidity stress, S. kraussei 0657L exhibited an enrichment of differentially expressed genes (DEGs) involved in glycolysis/gluconeogenesis, fatty acid metabolism, and glycerophospholipid metabolism pathways. This indicates that S. kraussei 0657L regulated energy metabolism to adapt to low-humidity stress. These findings provide insights into the mechanisms underlying drought resistance in EPNs and offer an experimental basis for their application in arid environments.

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