| Most insects are closely associated with bacterial symbionts that have ecological and evolutionary effects on their hosts.The communities of symbionts associated with aphids are diverse and the pea aphid-symbiont symbiosis is one of the most widely studied models for understanding interactions between insects and symbionts.To date,however,bacterial communities of most aphid species are still poorly characterized and even less about that of social aphids.Pseudoregma bambucicola is one social aphid species that widely distributed in subtropical areas.P.bambucicola can produce different aphid morphs during its whole life cycle.In some areas,P.bambucicola has completely lost their sex generation,and has been parthenogenesis all year round with feeding on hard bamboo stalks exclusively.Ant attendance in this species is associated with aphid clony size and soldier production rate.This study systematically detected the symbiotic bacterial community of P.bambucicola to explore whether there is a connection between symbiotic bacteria and some specific biological characteristics,such as the exculsive utilization of bamboos,differentiation of morphs and ant attendance.In this study,16S rDNA amplicon high-throughput sequencing approach was used to assess the entire bacterial communities of winglessadult individuals that collected from different seasons of a year and also11 different morphs and developmental stages of P.bambucicola.Then the influence of time series,ant attendance,growth duration and aphid morphs on the symbiotic bacterial diversity of this aphid was explored.In addition,high-throughput sequencing and molecular cloning of 16S rDNA were used to locate the dominant symbiotic bacteria within the body of P.bambucicola.The main results are as followed.In the wingless adult,the relative abundance and infection rate of Buchnera,Pectobacterium,Wolbachia in all samples were 89.07%,6.56%,0.97% and 100%,92.85%,82.14%,respectively.In terms of Alpha diversity,aphid groups with ant attendance had a significantly higher diversity of bacterial symbionts than that of without ant attendecce,but there was no significant difference in the diversity of bacterial communities of P.bambucicola clonies for 4 different time series groups.In different morphs and developmental stages of P.bambucicola,the average relative abundance of Buchnera,Pectobacterium and Wolbachia in all samples were 67.67%,10.30% and 7.14% respectively,and were distributed in all samples.Moreover,the relative abundance of these three symbiotic bacteria ranked the top three in most samples.Buchnera was the dominant bacteria in the morphs of soldier,first-instar non-soldier,wingless adult,four-instar winged nymph,winged adult and female,while Serratia(60.47%)and Acinetobacter(52.44%)were the dominantbacteria of the medium instar of non-soldier and the male respectively.The Alpha diversity of bacterial communities of the male was significantly higher than that of other morphs or developmental stages of P.bambucicola.Combined with the R2 value and R-value of permutational multivariate analysis of variance and analysis of similarities,results showed that grouping by morphs or developmental stages had a high degree of interpretation for the difference in the composition of symbiotic bacteria,and the difference between groups were large.Buchnera,Pectobacterium and Wolbachia were all distributed in the ovary,gut,bacteriome,salivary gland and other tissues except the four mentioned above.Wolbachia was mainly distributed in gut and salivary gland.The relative abundance of the three symbiotic bacteria in the ovary and bacteriome was similar to each other.In summary,Buchnera,Pectobacterium and Wolbachia stably exist in P.bambucicola.The diversity of symbiotic bacterial community of different P.bambucicola morphs can vary,and the dominant symbiotic bacteria in some morphs of P.bambucicola were different from that of others.Notebly,the Pectobacterium genus has been detected as symbiotic bacteria in aphids for the first time.Pectobaterium has been known as an important plant pathogen that could produce plant cell wall-degrading enzymes which make plant tissue decay efficiently.The results suggestthat Pectobacterium may help P.bambucicola pierce into the hard bamboo stem epidermis to suck phloem sap.Wolbachia is mainly distributed in the gut and salivary gland,suggesting that it may participate in the nutrient absorption of aphid host together with Pectobacterium. |
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