Effects Of Low Temperature And Ascarosides On The Sleep-inducing In Bursaphelenchus Xylophilus

As an important factor of ecological environment,temperature profoundly affected the ecological distribution of Bursaphelenchus xylophilus.Therefore,we studied the nematode's response to low temperature and its ecological adaption mechanism.In this study,fraction quiescent,free sugars,polyols and ascarosides content were measured after 25? and 4? treated for 48 hours,and we investigated the effects of ascarosides on fraction quiescent at 25?.The fraction quiescent of all ages,including L2,L3,L4 and adult worms,increased significantly at 4? than that of the control at 25?.After treatment with crude extract,the resting rate of pine wood nematode increased rapidly in 6-9 hours compared with the control.At 9 hours,the resting rate was the highest,about 100%,and the difference reached a significant level.After 9-12 hours,the resting rate maintained at about 100%.After about 3 hours,the resting rate gradually decreased,reaching the lowest value at 27 hours,which was only 1.1%.Trehalose content was remarkably higher,which were 2.32 times of that of the control,while sorbitol,glucose and glycerol were not,and the ascarosides determination showed that the contents of C5,C6 and ?C6 decreased,C7 and ?C9-secreting were ceased,while C9 began to secrete at 4?.Simultaneously,bioassay showed that crude extracts,C6,C7 and C9 could significantly increase fraction quiescent at 25?.Several ascarosides were involved in the regulation of pressure-induced sleep at low temperature in Bursaphelenchus xylophilus.Compared with the normal temperature condition at 25 ?,the expression levels of acy-1-1,egl-4-1,kin-29-1,lag-1-1 and let-23-1 genes were down-regulated at 4 ~C,regardless of the age of L2,L3,L4 or adults,suggesting that the metabolic level of pine wood nematode was down-regulated and its life activities were inhibited under low temperature stress,but kin-1-1 gene was inhibited in pine wood nematode L3 and adults.On the contrary,the expression level increased significantly,which may play a role in inducing sleep and coping with low temperature stress.