Trehalose Promote Bursaphelenchus Xylophilus Survival Under Low Temperature

Pine wood nematode(B.xylophilus)is the first-level hazardous forestry pest in China.Since it invaded into China in 1982,it is like a "cancer".And it has been spreading rapidly and its spread situation has been getting stronger and stronger,caused serious damage to Chinese forest ecosystem.It is an indisputable fact that B.xylophilus could survive in Northeast of China,where is cold in winter.However,the time of B.xylophilus invaded into Northeast of China was short,the research of low temperature response was insufficient.Therefore,in this paper,the survival rate and the population growth rate of pine wood nematodes under different temperatures,transcriptome sequencing and RNA interference,to study the mechanism of B.xylophilus low temperature responce.The main contents and results are as follows:1.By comparing the population growth rate of NXY61 strain and DL strain under optimal temperature and low temperature stress,as well as the survival rate of low temperature stress,it was found that the population growth rate of DL strain under low temperature stress was faster and the survival rate was higher.At-5℃,the DL strain still maintained a certain survival rate at the fifth day;2.DL strain was inoculated to healthy P.thunbergii branches and subjected them to low temperature stress at-5℃.After 8 hours,the nematodes were isolated,RNA was extracted,and transcriptome sequencing was performed.According to the analysis of different expressed genes,there were a total of 2181 genes with significant differences in expression,of which 1419 genes were significantly up-regulated and 762 genes were significantly down-regulated.GO analysis was used to further analysis,it was screened that the insulin-like growth factor receptor gene Bx-daf 2,which was in the regulatory position of various DEG pathways after 8 hours under low temperature stress;3.siRNA soaking method was used to perform RNA interference of Bx-daf-2,and transcriptome sequencing was performed after RNA interference.According to the analysis of different expressed genes,there were a total of 303 genes with significant differences in expression.There were genes which expression levels affected by Bx-daf-2 RNA interference.Among them,139 genes were significantly up-regulated and 164 genes were significantly down-regulated.Using co-expressed gene analysis to screen the different expressed genes which has the same expression changes between the transcriptome of the Bx-daf-2 gene RNA interference and the transcriptome of low temperature stress,and the trehalase gene Bx-tre-1was screened;4.By using low temperature stress,RNA interference,trehalase activity determination,trehalose content determination and survival rate determination,the function of Bx-tre-1 gene in low temperature response of B.xylophilus was studied-B.xylophilus trehalase gene Bx-tre-1 participated in the response to low temperature,during 1 d and 5 d,at-5℃ the expression of Bx-tre-1 gene was down-regulated,caused that the activity of Bx-TRE enzyme to decrease and the trehalose content increased,contributed to the improvement of the survival rate of B.xylophilus under-5℃.The above results showed that B.xylophilus had the ability of adapting to environmental temperature changes,and DL strain was more suitable for survival in low temperature environment;the increase of trehalose promoted the survival of B.xylophilus under low temperature.