A genomic perspective on nutrient provisioning by bacterial symbionts of insects
A genomic perspective on nutrient provisioning by bacterial symbionts of insects
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DOI：
10.1073/pnas.2135345100
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发表时间：
2003-11-25
影响因子：
11.1
通讯作者：
Wilcox, JL
中科院分区：
文献类型：
--
作者：
Moran, NA;Plague, GR;Wilcox, JL
许多动物表现出与细菌共生体的密切相互作用，这些共生体为宿主提供有限的营养。最好的研究，这种协会是蚜虫和Buchnera aphidicola，它产生的必需氨基酸是罕见的韧皮部汁液饮食之间。Buchnera的基因组研究提供了一种新的手段来推断代谢能力的共生体和他们可能的贡献主机。尽管基因组大小的进化减少，涉及大多数祖先基因的丢失，但Buchnera保留了所有必需氨基酸的生物合成能力。相反，大多数复制宿主氨基酸生物合成能力的基因已经被消除。在许多蚜虫的Buchnera中，亮氨酸和色氨酸的生物合成基因已从染色体转移到独特的质粒中，这一特征被解释为通过基因扩增过量生产这些氨基酸的机制。然而，质粒相关扩增的程度在物种之间和物种内不同，并且质粒携带的基因有时在数量上少于（多倍体）主染色体上的单拷贝基因。这支持质粒定位作为实现基因拷贝数和/或转录的调控的手段的更广泛的解释。Buchnera基因组已经消除了大多数调控序列，提出了基因表达在多大程度上受到宿主营养或其他因素变化的影响的问题。布赫内拉转录组的微阵列分析显示，响应宿主饮食的变化，营养相关基因的表达只有轻微的变化，与相关的非共生物种，大肠杆菌所观察到的反应不那么引人注目。
Many animals show intimate interactions with bacterial symbionts that provision hosts with limiting nutrients. The best studied such association is that between aphids and Buchnera aphidicola, which produces essential amino acids that are rare in the phloem sap diet. Genomic studies of Buchnera have provided a new means for inferring metabolic capabilities of the symbionts and their likely contributions to hosts. Despite evolutionary reduction of genome size, involving loss of most ancestral genes, Buchnera retains capabilities for biosynthesis of all essential amino acids. In contrast, most genes duplicating amino acid biosynthetic capabilities of hosts have been eliminated. In Buchnera of many aphids, genes for biosynthesis of leucine and tryptophan have been transferred from the chromosome to distinctive plasmids, a feature interpreted as a mechanism for overproducing these amino acids through gene amplification. However, the extent of plasmid-associated amplification varies between and within species, and plasmid-borne genes are sometimes fewer in number than single copy genes on the (polyploid) main chromosome. This supports the broader interpretation of the plasmid location as a means of achieving regulatory control of gene copy number and/or transcription. Buchnera genomes have eliminated most regulatory sequences, raising the question of the extent to which gene expression is moderated in response to changing demands imposed by host nutrition or other factors. Microarray analyses of the Buchnera transcriptome reveal only slight changes in expression of nutrition-related genes in response to shifts in host diet, with responses less dramatic than those observed for the related nonsymbiotic species, Escherichia coli.