| Insect symbionts play an important role in physiological metabolic process of their hosts,such asnutrition metabolism,immunity,reproduction and detoxification.Many endosymbionts increase their hosts5 fitness by enhancing their hosts’ detoxification of toxic plant metabolites to ensure the spread and outbreaks of their hosts.Tetranychus truncatus,a major pest in China,has been recognized as one of the most notorious pests because of its small size,fast reproduction,strong resistance to acaricide.Recnetly,T.truncatus is more and more rampant,and put great danger and threat to the yield and quality of crops.Previous study found that T.truncatuswas frequently associated with multiple endosymbionts.Endosymnionts play an important role in facilitating their hosts’ spread and outbreaks by changing their hosts’ physiological metabolism,controlling reproduction and fitness.However,there are less research about how endosymbionts regulate their hosts’ reproduction and detoxification.Considering the significance of symbionts to their hosts,it is necessary to explore how they regulate their hosts,detoxification and the molecular mechanism.In this study,we explored how antibiotic treatment influenced the symbiotic bacteria of T.truncatus.Then we established the same genetic background T.truncatus strains(Wolbachia-Spiroplasmainfected strain and Wolbachia-Spiroplasma uninfected strain)by using antibiotic.Secondly,we studied how the double infection of Wolbachia and Spiroplasma influence their hosts’ fitness to clear and define the impact of endosymbionts during the development of T.truncatus.Finanlly,we investigated how endosymbionts influence their hosts’ detoxification to reveal the molecular mechanism of how endosymbionts regulate their hosts’ fitness.Our main results are as follows.1.How antibiotic treatment influence the symbotic bacterial communityWe studied how antibiotic treatment influence the symbiotic bacteria community by combining 16S rRNA amplicon high-throughput sequencing technology and qRT-PCR technology.The results showed that 297 OTUs were obtained totally.There were 12 phyla and 123 genura in antibiotic treated T.truncatusstrain and 13 phyla and 128 genura in antibiotic untreated T.truncates strain.After antibiotic treatment,Wolbachiaand Spiroplasma were removed completely.We tested it by using qRT-PCR technology,and we confirmed that Wolbachiaand Spiroplasnza were disappeared.This research result provided a reliable method for the establishment of the infected and uninfected Wolbachia-Spiroplasma T.truncatus strain.2.How endosymbionts influence the fitness of T.truncatusEndosymbionts can change their hosts’ fitness,however,there were less research about it.We use the screened Wolbachia-Spiroplasma infected and uninfected T.truncatus strains as material to investigate the fitness effect of Wolbachia-Spiroplasma to their hosts.We found that 1)infection with Wolbachia-Spiroplasma can increase their hosts’ oviposition significantly.2)There were not significant differences in hatchability and proportion of males between Wolbachia-Spiroplasma infected and uninfected T.truncatus strains.3)Survival curve during 30 days of Wolbachia-Spiroplasma infected T.truncatus is higher than uninfected T.truncatus strain.We finally found that endosymbiosis could increase their hosts’ fitness.3.Detoxification regulation of double infection with Wolbachia-Spiroplasma to their hostsEndosymbiosis can change the detoxification of insects on plant secondary substances utilization and then influence the production of their hosts.We found that endosymbiosis can increase their hosts’ fitness,however,the regulation mechanism is still unknown.Therefore,we need to study the detoxification effect of endosymbiosis on T.truncatus.We found that 1)with the increase of age,the detoxification enzyme activity and detoxification gene expression of T.truncatus increased.2)At the corresponding age,there were not significant differences in detoxification enzyme activity and detoxification genes between the infected and uninfected T.truncatus.3)Titer of Wolbachia was positively correlated with p450s enzyme activity of the host while negatively correlated with GSTs enzyme activity.In conclusion,this study identified the changes in the diversity o.f symbiotie bacteria in T.truncatus,especially the titers of endosymbiosis,and provided methods for the establishment of infected and uninfected T.truncatus strains.The influence of endosymbiosis on the fitness of T.truncatus was elucidated.From the perspective of the detoxification effect of sendosymbiosis on the host.the molecular mechanism of endosy mbiosis to improve the hosts’ fitness was revealed.The results of the study will behelpful to understand the interaction between the symbiotic bacteria and the host,and provide guidance for the comprehensive prevention and control of the pest. |
