AUTHOR=Qian Li , Jia Fan , Jingxuan Sun , Manqun Wang , Julian Chen 

TITLE=Effect of the Secondary Symbiont Hamiltonella defensa on Fitness and Relative Abundance of Buchnera aphidicola of Wheat Aphid, Sitobion miscanthi

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00582

DOI=10.3389/fmicb.2018.00582

ISSN=1664-302X

ABSTRACT=<p>Bacterial symbionts associated with insects are often involved in host development and ecological fitness. In aphids, the role of these symbionts is variable and not fully understood across different host species. Here, we investigated the symbiont diversity of the grain aphid, <italic>Sitobion miscanthi</italic> (Takahashi), from 17 different geographical areas. Of these, two strains with the same symbiont profile, except for the presence of <italic>Hamiltonella defensa</italic>, were selected using PCR. The <italic>Hamiltonella</italic>-infected strain, YX, was collected from a Yuxi wheat field in Yunnan Province, China. The <italic>Hamiltonella</italic>-free strain, DZ, was collected from a Dezhou wheat field in Shandong Province, China. Using artificial infection with <italic>H. defensa</italic> and antibiotic treatment, a <italic>Hamiltonella</italic>-re-infected strain (DZ-H) and <italic>Hamiltonella</italic>-significantly decreased strain (DZ-HT) were established and compared to the <italic>Hamiltonella</italic>-free DZ strain in terms of ecological fitness. Infection with the DZ-H strain increased the fitness of <italic>S. miscanthi</italic>, which led to increases in adult weight, percent of wingless individuals, and number of offspring. Meanwhile, decreased abundance of <italic>H. defensa</italic> (DZ-HT strain) resulted in a lower adult weight and wingless aphid rate compared to the DZ-H strain. However, the indices of longevity in both the DZ-H and DZ-HT strains decreased slightly, but were not significantly different, compared to the DZ strain. Furthermore, quantitative PCR showed that the relative abundance of the primary symbiont <italic>Buchnera aphidicola</italic> in the DZ-H strain was significantly higher than in the DZ strain in all but the first developmental stage. These results indicate that <italic>H. defensa</italic> may indirectly improve the fitness of <italic>S. miscanthi</italic> by stimulating the proliferation of <italic>B. aphidicola</italic>.</p>