Diversity Of Symbiotic Bacteria In Aphis Aurantii

Aphis aurantii(Hemiptera : Aphididae)is a pest species for subtropical agriculture and forestry,which can feed on various of economic crops,such as grapefruit,citrus,tea,etc.A.aurantii are widely distributed in southern China.Based on the phylogenetic analysis of COI and gnd genes,previous research found A.aurantii feeding on Ficus plants(AFP)formed a separate clade and A.aurantii collected from various other host plants(ADP)in Fuzhou city were gathered on another clade.According to the genetic distances between AFP and ADP,the AFP showed obvious population differentiation.Investigation of the bacterial diversity in A.aruantii can help figure out the association between symbionts and host plant utilization.It is also important to uncovering the coevolution between symbionts,aphid host and host plants.Understanding the relationships between bacteria,aphids and host plants may also be helpful for pest control.This research aimed to investigate the diversity of symbionts in A.aurantii collected from 10 families of host plants by using high-throughput technology.Based on the high-throughput data,the 16 S rRNA sequences of relative bacteria of AFP would be obtained through molecular cloning experiment.The homology of sequences,genetic distances and phylogenetic relationship of relative bacteria would be performed to explain evolutionary pattern.In addition,fluorescence in situ hybridization and transmission electron microscopy would be performed to located related symbionts.The main results obtained are as followed:Based on high-throughput technology,the bacterial 16 S rRNA V3-V4 regions were examined in each A.aurantii samples which were collected from different host plants,it was found that the symbionts were mainly distributed in Proteobacteria.Although,at the level of family,the dominated symbionts in all A.aurantii samples were from Enterobacteriaceae,the relative abundance of Rickerrsiaceae and Orbaceae were significantly higher in Hamamelidaceae and Moraceae plants,respectively.At the level of genus,the relative abundance of Serratia in Rubiaceae sample were higher than Buchnera which were still the dominated bacteria in other plants.In Theaceae,the secondary dominated symbiont was Serratia.In Moraceae samples,the secondary dominated bacteria were annotated as ‘Gilliamella'.There were large differences in bacterial composition and abundances between the family of Hamamelidaceae.Based on the NJ tree of OTU sequences,showed the ‘Gilliamella' of AFP and Gilliamella from bees did not gathered at the same clade.The whole length of 16 S rRNA gene of the special bacteria in AFP were obtained by molecular cloning experiment.The homology of sequences,genetic distances and the phylogenetic reconstruction was performed between ‘Gilliamella' and the Orbaceae bacteria.The results indicated the specific bacteria in AFP showed differences with Gilliamella which were isolated from bees,neither in homology of sequences(92.80~94.70%)or genetic distances(0.053~0.075)and the special bacterial sequences of AFP gathered alone as a cluster.Based on that,the specific bacteria in AFP should be classified as a new bacterial genus in Orbaceae and we given the name ‘Candidatus Zhangtaonella aphidicola' for it.The location of ‘Ca.Zhangtaonella aphidicola' by FISH and transmission electron microscope showed that the distribution of this bacteria in A.aurantii was not the same as previously symbionts in aphids,mainly located inside the intestinal epithelial cellsIn summary,this research investigated the diversity of bacteria of A.aurantii in different host plants in Fuzhou city and Proved that the composition of symbionts was different within Rutaceae,Theaceae and Moraceae.Futhermore,we also found even feed on the same plant,there still have some differences in bacterial relative abudances.There exited specific bacteria in AFP,the bacteria should be a new bacterial genus in Orbaceae family based on the phylogenetic tree and a candidatus name ‘Ca Zhangtaonella aphidicola' was been given.‘Ca Zhangtaonella aphidicola' were located inside the intestinal epithelial cells.The bacteria may be involved with the function about the detoxication of Ficus sap and the bacteria may help A.aurantii feeding on Ficus plants.Furthermore,‘Ca Zhangtaonella aphidicola' may lead to the speciation of AFP and it also may be undergoing the period from free-living to endosymbiont.