Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Hokkaido Center, 2-17-2-1 Tsukisamu-Higashi, Toyohira, Sapporo 062-8517, Japan.
Appl Environ Microbiol. 2011 Jun;77(12):4075-81. doi: 10.1128/AEM.00358-11. Epub 2011 Apr 29.
The alydid stinkbug Riptortus pedestris is specifically associated with a beneficial Burkholderia symbiont in the midgut crypts. Exceptional among insect-microbe mutualistic associations, the Burkholderia symbiont is not vertically transmitted but orally acquired by nymphal insects from the environment every generation. Here we experimentally investigated the process of symbiont acquisition during the nymphal development of R. pedestris. In a field population, many 2nd instar nymphs were Burkholderia free, while all 3rd, 4th, and 5th instar nymphs were infected. When reared on soil-grown potted soybean plants, Burkholderia acquisition occurred at a drastically higher frequency in the 2nd instar than in the other instars. Oral administration of cultured Burkholderia cells showed that 2nd and 3rd instar nymphs are significantly more susceptible to the symbiont infection than 1st, 4th, and 5th instar nymphs. Histological observations revealed rudimentary midgut crypts in the 1st instar, in contrast to well-developed midgut crypts in the 2nd and later instars. These results indicate that R. pedestris acquires the Burkholderia symbiont from the environment mainly during the 2nd instar period and strongly suggest that the competence for the symbiont infection is developmentally regulated by the host side. Potential mechanisms involved in infection competence and possible reasons why the infection preferentially occurs in the 2nd instar are discussed.
淡色蜡蝉 Riptortus pedestris 与中肠隐窝中的有益 Burkholderia 共生体密切相关。在昆虫-微生物共生关系中，Burkholderia 共生体是一个例外，它不是垂直传播的，而是由每一代的若虫从环境中通过口获得。在这里，我们通过实验研究了 R. pedestris 若虫发育过程中共生体的获得过程。在一个野外种群中，许多 2 龄若虫是 Burkholderia 自由的，而所有 3 龄、4 龄和 5 龄若虫都被感染了。当在土壤中生长的盆栽大豆植物上饲养时，Burkholderia 的获得率在 2 龄时比其他龄期高得多。口服培养的 Burkholderia 细胞表明，2 龄和 3 龄若虫比 1 龄、4 龄和 5 龄若虫更容易感染共生体。组织学观察显示，1 龄若虫的中肠隐窝是原始的，而 2 龄及以后的若虫的中肠隐窝则发育良好。这些结果表明，R. pedestris 主要在 2 龄期从环境中获得 Burkholderia 共生体，并强烈表明宿主方面的发育调控了共生体感染的能力。讨论了感染能力涉及的潜在机制以及感染为什么优先发生在 2 龄期的可能原因。
