Influence Of Different Antimicrobial Substances On The Diversity Of Symbionts In Brown Planthopper,Nilaparvata Lugens St(?)l

There are a large number of endosymbionts in the brown planthopper(BPH)Nilaparvata lugens St(?)l,which have the diversity not only in species but also in functions on their host.Symbionts play a vital role in the growth,development,reproduction,nutrition metabolism,resistance variation and immune function on BPH.By comparing the effects of 7 kinds of antimicrobials on brown planthopper survival rate and its yeast-like symbionts(YLS)number,3 dominant antimicrobials were screened preliminarily.The diversity of fat body and gut symbionts of BPH treated with these three antimicrobials was analysed by amplicon sequencing technology.In addition,the detection method of symbionts number was established in the gut and fat body of BPH.Furthermore,the changes of the number of symbiotic bacteria and fungi in the gut and fat body of BPH treated with different antimicrobials were researched.The results are as follows:1.The results of 7 antimicrobials treatment after 1 d、2 d、4 d showed that the number of YLS and the survival rate of BPH both significantly decreased.It showed that metabolites of Streptomyces diastatochromogenes(SD1628)、tebuconazole,75%tebuconazole& trifloxystrobin and Zhongshengmycin had the better inhibition effects on YLS and its host BPH.2.Diversity and dynamics of microbial communities in gut and fat body of BPH treated with three antimicrobials were analyzed using high-throughput amplicon sequencing.The results showed that there were significant differences in gut microbial communities structures of BPH between different antimicrobials treatment with negative control.The antimicrobials reduced the fungal diversity by reducing the non-dominant fungi abundance,and increased bacterial diversity by inhibiting the dominant bacteria Acinetobacter in the gut.The diversification of taxonomic groups in gut depended on the different selective stress of antimicrobials.In addition,we found that the antimicrobials reduced bacterial diversity and increased fungal diversity in the fat body and altered the bacterial and fungal community structure.The relative abundance of Serratia increased,indicating that Serratia,which was the most dominant in the fat body,is an important symbiont perhaps involved in resistance to antimicrobials.After antimicrobial exposure,seven genera such as Wolbachia,Legionella,Chromobacterium,which probably participated in the nutrition and development function of the host,were totally eliminated from the fat body.Changes in the diversity of symbionts in BPH treated with these antimicrobials will benefit to control brown planthopper with other pesticides.3.This study established a detection method for endosymbionts in the gut and fat body of BPH.Furthermore,the changes of the number of symbionts in the gut and fat body of BPH with different antimicrobials treatment were researched.The study found that the total number of gut symbionts significantly decreased after antimicrobials treated.The number of symbionts in most genera also decreased,including Acinetobacter and unclassified Hypocreales,which is closely related to BPH life activities.The number of Serratia was significantly increased in SD1628 and tebuconazole group.In the fat body,the total number of symbionts also significantly decreased after antimicrobials treated,but the effect on the number of symbionts by three antimicrobials in the fat body was different from the gut.The number of Serratia was significantly increased after antimicrobials treated,and the number of unclassified K＿fungi was increased by the treatment of tebuconazole and zhongshengmycin,which means these two genera of symbionts may related to the resistance of BPH to antimicrobials.