Identification of Autophagy in the Pine Wood Nematode Bursaphelenchus xylophilus and the Molecular Characterization and Functional Analysis of Two Novel Autophagy-Related Genes, BxATG1 and BxATG8.

Li-Na Deng,Xiao-Qin Wu,Qi Xue,Jian-Ren Ye

doi:10.3390/ijms17030279

Li-Na Deng, Xiao-Qin Wu + Show 2 more

Open Access

https://doi.org/10.3390/ijms17030279

Copy DOI

Abstract

The pine wood nematode, Bursaphelenchus xylophilus, causes huge economic losses in pine forests, has a complex life cycle, and shows the remarkable ability to survive under unfavorable and changing environmental conditions. This ability may be related to autophagy, which is still poorly understood in B. xylophilus and no autophagy-related genes have been previously characterized. In this study, transmission electron microscopy was used to confirm that autophagy exists in B. xylophilus. The full-length cDNAs of BxATG1 and BxATG8 were first cloned from B. xylophilus, and BxATG1 and BxATG8 were characterized using bioinformatics methods. The expression pattern of the autophagy marker BxATG8 was investigated using in situ hybridization (ISH). BxATG8 was expressed in esophageal gland and hypodermal seam cells. We tested the effects of RNA interference (RNAi) on BxATG1 and BxATG8. The results revealed that BxATG1 and BxATG8 were likely associated with propagation of nematodes on fungal mats. This study confirmed the molecular characterization and functions of BxATG1 and BxATG8 in B. xylophilus and provided fundamental information between autophagy and B. xylophilus.

Highlights

Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle is the pine wood nematode that is the causal agent of pine wilt disease (PWD), which results in large economic losses [1]
This study focused on the autophagy, which was identified by transmission electron microscopy (TEM) under starvation, in B. xylophilus
The molecular characterization and functional analysis by in situ hybridization (ISH) and RNA interference (RNAi) of BxATG1 and BxATG8 from B. xylophilus indicated these autophagy genes are associated with development and reproduction

Summary

Introduction

Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle is the pine wood nematode that is the causal agent of pine wilt disease (PWD), which results in large economic losses [1]. There are many different hypotheses to explain the pathogenesis of PWD, such as the cellulose (which suggests that the destruction of pine cells is triggered by cell wall-degrading enzymes, such as cellulose), phytotoxin and terpenoid hypotheses [7,8,9], but the pathogenic mechanism of B. xylophilus remains unknown. Under unfavorable environmental conditions, such as limited food and cooler temperatures, the second-stage propagative juvenile molts into the third-stage dispersal juvenile, they molt into specialized dispersal-stage dauer juvenile [10,11]. B. xylophilus shows a remarkable adaptability to changing environmental conditions, but the mechanism behind this adaptability is still not well understood. Under conditions of high population density, limited food or increased temperature, Caenorhabditis elegans nematodes can induce the process of autophagy [12,13]. Does autophagy assist the nematodes’ responses to various changing environmental conditions and allow them to invade pine trees successfully? Does the process of autophagy exist in B. xylophilus? Does autophagy assist the nematodes’ responses to various changing environmental conditions and allow them to invade pine trees successfully?

Methods

Results

Discussion

Conclusion