Genetic characteristics of Bursaphelenchus xylophilus third-stage dispersal juveniles.

The third-stage dispersal juvenile (DJ3) of pinewood nematode (PWN) is highly associated with low-temperature survival and spread of the nematode. Oil-Red-O staining showed that its lipid content was significantly higher compared with other PWN stages. Weighted gene coexpression network analysis identified that genes in the pink module were highly related to DJ3 induced in the laboratory (DJ3-lab). These genes were arranged according to their gene significance (GS) to DJ3-lab. Of the top 30 genes with the highest GS, seven were found to be highly homologous to the cysteine protease family cathepsin 1 (CATH1). The top 30 genes with the highest weight value to each of the seven genes in the pink module were selected, and finally 35 genes were obtained. Between these seven CATH1 homologous genes and their 35 highly related genes, 15 were related to fat metabolism or autophagy. These autophagy-related genes were also found to be highly correlated with other genes in the pink module, suggesting that autophagy might be involved in the mechanism of longevity in DJ3 and the formation of DJ3 by regulating genes related to fat metabolism.