Transcriptome Sequencing Reveals Large-Scale Changes in Axenic Aedes aegypti Larvae.
Transcriptome Sequencing Reveals Large-Scale Changes in Axenic Aedes aegypti Larvae.
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转录组测序揭示了埃及埃及幼虫的大规模变化。
DOI：
10.1371/journal.pntd.0005273
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发表时间：
2017-01
影响因子：
3.8
通讯作者：
Strand MR
中科院分区：
文献类型：
--
作者：
Vogel KJ;Valzania L;Coon KL;Brown MR;Strand MR
蚊子的消化道中主要由细菌组成的微生物群落。我们以前报道过，埃及伊蚊幼虫被原生细菌群落定植，与仅被大肠杆菌定植的非生生物幼虫发育成成虫非常相似，而无性系幼虫从不蜕皮，并在一龄时死亡。在这项研究中，我们扩展了这些发现，首先比较了常规、非生和无菌幼虫在第一龄期间的细菌生长和丰度。结果表明，传统幼虫和非生菌幼虫在生长、蜕皮时间和消化道细菌数量方面没有差异。相比之下，不育幼虫生长最小，从未达到与传统和非生食幼虫相关的临界尺寸。在研究的第二部分，我们通过对孵化后22 h的肠道和非肠道组织（胴体）进行RNAseq分析，比较了传统、非肠道和无菌幼虫的基因表达模式。约12%的Ae。埃及伊蚊转录本在无性系与常规或无食幼虫中表达差异。然而，该基因谱主要由7类转录本组成，包括肠道中特定肽酶的下调和肠道和胴体中氨基酸运输、激素信号传导和代谢相关基因的上调。总的来说，我们的研究结果表明，不育幼虫表现出基因表达的改变与生长所需营养物质的获取和同化缺陷一致。包括埃及伊蚊在内的几种蚊子在成年后传播病原体，导致人类和其他脊椎动物患病。人们也早就知道，蚊子的消化道中含有细菌，这些细菌主要是在幼虫期获得的，然后经尿道传播给成虫。我们最近的研究结果表明，缺乏细菌的无菌幼虫不会发育到一龄以上，而有活细菌的幼虫则发育到成虫。为了更好地了解细菌对蚊子发育的影响，我们比较了伊蚊幼虫的生长、蜕皮和基因表达。含有几种细菌的埃及伊蚊，只有一种细菌（大肠杆菌），或者没有细菌。结果表明，含有多种大肠杆菌或仅含有大肠杆菌的幼虫生长和蜕皮相似，而不含大肠杆菌的幼虫生长很少且不蜕皮。一些Ae。埃及伊蚊调节生长的基因在无细菌幼虫和有细菌幼虫中的表达存在差异。总的来说，我们的研究结果表明，没有细菌的蚊子幼虫由于吸收营养物质的缺陷而不能生长或蜕皮。
Mosquitoes host communities of microbes in their digestive tract that consist primarily of bacteria. We previously reported that Aedes aegypti larvae colonized by a native community of bacteria and gnotobiotic larvae colonized by only Escherichia coli develop very similarly into adults, whereas axenic larvae never molt and die as first instars. In this study, we extended these findings by first comparing the growth and abundance of bacteria in conventional, gnotobiotic, and axenic larvae during the first instar. Results showed that conventional and gnotobiotic larvae exhibited no differences in growth, timing of molting, or number of bacteria in their digestive tract. Axenic larvae in contrast grew minimally and never achieved the critical size associated with molting by conventional and gnotobiotic larvae. In the second part of the study we compared patterns of gene expression in conventional, gnotobiotic and axenic larvae by conducting an RNAseq analysis of gut and nongut tissues (carcass) at 22 h post-hatching. Approximately 12% of Ae. aegypti transcripts were differentially expressed in axenic versus conventional or gnotobiotic larvae. However, this profile consisted primarily of transcripts in seven categories that included the down-regulation of select peptidases in the gut and up-regulation of several genes in the gut and carcass with roles in amino acid transport, hormonal signaling, and metabolism. Overall, our results indicate that axenic larvae exhibit alterations in gene expression consistent with defects in acquisition and assimilation of nutrients required for growth. Several mosquito species including Aedes aegypti transmit pathogens as adults that cause disease in humans and other vertebrates. It has also long been known that mosquitoes host bacteria in their digestive tract, which are primarily acquired during the larval stage and transstadially transmitted to adults. Our recent results indicate that axenic larvae, which lack bacteria, do not develop beyond the first instar, whereas larvae with living bacteria develop into adults. To better understand the effects of bacteria on mosquito development, we compared growth, molting and gene expression in larval Ae. aegypti that contained several species of bacteria, only one species of bacterium (Escherichia coli), or no bacteria. Results showed that larvae containing several species or only E. coli grew and molted very similarly while larvae with no bacteria grew minimally and never molted. A number of Ae. aegypti genes with roles in regulating growth were differentially expressed in larvae without bacteria when compared to larvae with bacteria. Overall, our results indicate that mosquito larvae without bacteria do not grow or molt because of defects in assimilating nutrients.