The Impact Of Encarsia Sophia Parasitization On Development And The Exploration Of Regulatory Mechanism Of Bemisia Tabaci

Bemisia tabaci is an invasive agricultural pest all over the world damaging seriously.In recent years,as a dominant parasitoid wasp of B.tabaci,Encarsia sophia plays an important role in biological control of B.tabaci.Revealing the interaction mechanisms between the parasitoid and the host could better excavate and utilize the potency of the parasitoid.In the article,Q biotype B.tabaci and E.sophia were selected to study.We found abundant differential expression genes through transcriptome sequencing and analysis of parasitized B.tabaci nymph in the 24h and 72h after parasitization.Next,the real-time expression levels of nine differential expression genes including serpin 12,cuticle protein 8 and citrate synthase were tested by quantitiative real time PCR(qRT-PCR)to verify the reliability of transcriptome data.In addition,we tested the trehalose content,trehalase activity and body length,width and volume of parasitized and non-parasitized B.tabaci nymph in order to further verify the regulation of E.sophia.1.Parasitization check by counting the number of punctureThe whitefly was dissected at 6h,12h and 24h after they had been parasitized.The punctu re number was recorded then.The ratios of whitefly with puncture number of one,two,thr ee or more than three were caculated at different time.Result showed that the more puncture numbers was,the higher parasitism there was at 6h after parasitization.But there was no significant relation between the number of puncture holes and parasitization rate at 12h or 24h.In the whitefly with same puncture holes,parasitization rates were stable at 12 hours after parasitism.These showed both parasitized time and number of puncture holes have an impact on parasitism.Take all in consideration,whitefly with more puncture holes was preferred to be regarded as parasitic group less than 12 hours after parasitized.More than 12 hours,the whitefly can be regarded as parasitized successfully as long as there is a puncture hole.2.The effect of parasitization by E.sophia on the body size and larvae development of B.tabaci nymphsWe tested the body length and width of parasitized and non-paras it ized B.tabaci nymphs in 24h,48h and 72h after parasitization and calculated the volumes.The result indicated that E.Sophia parasitization had no significant effect on the body size of B.tabaci nymphs.At the same time,we observed the development of parasitized and non-parasitized B.tabaci nymphs in the first day,second day,third day,fourth day and fifth day after parasitization.The result showed that the development progress had difference from the third day and the development of parasitized nymphs became slow.In the fourth day,tissues and organs of non-parasitized nymphs had formed basically but the compound eyes of parasitized nymphs were resolved obviously.In the fifth day,nymphsin the control group developed into pseudopupa,however the size of parasitized nymphs had decreased significantly.These results indicated that E.sophia could suppress B.tabaci nymphs developing into pseudopupa.However,the function may be not reflected by the way of body size.3.The gene expression changes of B.tabaci parasitized by E.sophiaWe selected 24h and 72h after parasitization as the time points transcriptome sequencing.The result showed that the transcriptional levels of 1,284 unigenes had significant difference in which 852 unigenes were up-regulated and 630 unigenes were down-regulated.The genes involved in immune defense response of B.tabaci were promoted to express in the 24h and 72h.It showed that B.tabaci had strong immune defense ability.However,the transcription of genes involved in protective enzymes,cell migration and cell movement of the host were suppressed significantly.It showed that E.sophia started immune defense.Meanwhile,E.sophia suppressed significantly the expression of pupal cuticle protein,arylphorin and increased the transcriptional level of larval cuticle protein.It showed that E.sophia suppressed the development of B.tabaci nymphs and caused nymphs can't develop into pseudopupa.In addition,E.sophia's parasitization induced stearoyl-CoA desaturase and insulin signaling pathway-related genes over expression in the 24h and 72h after parasitization,suggesting that E.sophia could regulated the nutritional level of the host.Over expression of genes involved in respiration and citric acid cycle indicated that E.sophia may have the ability of regulating the energy metabolism.Furthermore,the numbers and kinds of genes related to metabolism at the 72h were more than at the 24h after parasitization.It was likely that the moreenergy was needed in the larvae stageof E.sophia.4.The impact of parasitization by E.sophia on the content of trehalose and activity of trehalase in B.tabaci nymphsParasitization significantly influenced the content of trehalose and the activity of trehalase of the host.After paras it izat ion,the content of trehalose increased to the peak at 24h and then reduced.The trehalase activity reduced until 24h and then increased.24h after parasitization was the turning point of the trehalose content and trehalase activity.This timepoint may also be an important regulatory point of E.sophia.Under the same development conditions,the content of trehalose and the activity of trehalase of non-parasitized B.tabaci nymphs also fluctuated significantly.However,the invidudal difference is not similar as the variation caused by parasitization.