Putative Horizontally Acquired Genes, Highly Transcribed during Yersinia pestis Flea Infection, Are Induced by Hyperosmotic Stress and Function in Aromatic Amino Acid Metabolism
Putative Horizontally Acquired Genes, Highly Transcribed during Yersinia pestis Flea Infection, Are Induced by Hyperosmotic Stress and Function in Aromatic Amino Acid Metabolism
复制标题
DOI：
10.1128/jb.00733-19
复制
发表时间：
2020-06-01
影响因子：
3.2
通讯作者：
Vadyvaloo, Viveka
中科院分区：
文献类型：
--
作者：
Martinez-Chavarria, Luary C.;Sagawa, Janelle;Vadyvaloo, Viveka
鼠疫耶尔森氏菌是一种由跳蚤传播的导致鼠疫的细菌，在其生命周期中交替在昆虫和哺乳动物之间传播，它适当地调节其基因表达，以适应这两种生理上不同的宿主环境。在能够传播鼠疫杆菌的跳蚤中，低gc含量的基因y3555、y3551和y3550被高度转录，表明这些基因在跳蚤感染中具有高度优先的作用。在这里，我们证明了y3555、y3551和y3550是作为一个多顺反子mRNA的一部分转录的，该mRNA由y3555、y3554、y3553、y355x、y3551和y3550基因组成。此外，y355x-y3551-y3550组成另一个操纵子，而y3550也可以转录为单顺反子mRNA。这些基因的表达是由高渗盐度胁迫诱导的，这是一种明确的环境刺激，可以启动预测的y3550启动子的转录活性。Y3555与pyridoxal 5'-phosphate （PLP）依赖性芳香氨基转移酶具有同源性，而Y3550和Y3551与Rid蛋白超家族（YjgF/YER057/UK114）成员具有同源性，这些成员可以防止PLP依赖性酶活性过程中形成的活性中间体造成的损伤。我们证明y3551特异性编码具有2-氨基丙烯酸酯脱氨酶活性的原型RidA蛋白，而Y3550缺乏Rid脱氨酶功能。y3555的外源表达在肠沙门氏菌aspC突变体中产生了关键的天冬氨酸需求，而它的体外表达，特别是它与y3550的外源共表达，提高了大肠杆菌Delta aspC Delta tyrB突变体在规定的最低氨基酸补充培养基中的生长速度。我们的数据表明，y3555、y3551和y3550基因协同工作，优化芳香氨基酸代谢，并在高渗盐胁迫条件下被诱导。重要性鼠疫杆菌感染跳蚤和哺乳动物宿主时表达不同的基因库。许多这些基因的功能仍然是预测或未知的，因此有必要对其进行表征，因为这可能有助于更好地了解鼠疫杆菌对其两个宿主离散环境的专门生物适应。本研究通过解读其在(i)转录组织、（ii）转录激活信号和（iii）生化功能方面的基本过程，为在跳蚤宿主中主要表达的邻接集群水平获得性基因提供了功能背景。我们的数据支持这些基因在渗透适应和芳香氨基酸代谢中的作用，强调这些是跳蚤感染期间鼠疫杆菌基因表达调节的优先过程。
While alternating between insects and mammals during its life cycle, Yersinia pestis, the flea-transmitted bacterium that causes plague, regulates its gene expression appropriately to adapt to these two physiologically disparate host environments. In fleas competent to transmit Y. pestis, low-GC-content genes y3555, y3551, and y3550 are highly transcribed, suggesting that these genes have a highly prioritized role in flea infection. Here, we demonstrate that y3555, y3551, and y3550 are transcribed as part of a single polycistronic mRNA comprising the y3555, y3554, y3553, y355x, y3551, and y3550 genes. Additionally, y355x-y3551-y3550 compose another operon, while y3550 can be also transcribed as a monocistronic mRNA. The expression of these genes is induced by hyperosmotic salinity stress, which serves as an explicit environmental stimulus that initiates transcriptional activity from the predicted y3550 promoter. Y3555 has homology to pyridoxal 5'-phosphate (PLP)-dependent aromatic aminotransferases, while Y3550 and Y3551 are homologous to the Rid protein superfamily (YjgF/YER057/UK114) members that forestall damage caused by reactive intermediates formed during PLP-dependent enzymatic activity. We demonstrate that y3551 specifically encodes an archetypal RidA protein with 2-aminoacrylate deaminase activity but Y3550 lacks Rid deaminase function. Heterologous expression of y3555 generates a critical aspartate requirement in a Salmonella enterica aspC mutant, while its in vitro expression, and specifically its heterologous coexpression with y3550, enhances the growth rate of an Escherichia coli Delta aspC Delta tyrB mutant in a defined minimal amino acid-supplemented medium. Our data suggest that the y3555, y3551, and y3550 genes operate cooperatively to optimize aromatic amino acid metabolism and are induced under conditions of hyperosmotic salinity stress.IMPORTANCE Distinct gene repertoires are expressed during Y. pestis infection of its flea and mammalian hosts. The functions of many of these genes remain predicted or unknown, necessitating their characterization, as this may provide a better understanding of Y. pestis specialized biological adaptations to the discrete environments of its two hosts. This study provides functional context to adjacently clustered horizontally acquired genes predominantly expressed in the flea host by deciphering their fundamental processes with regard to (i) transcriptional organization, (ii) transcription activation signals, and (iii) biochemical function. Our data support a role for these genes in osmoadaptation and aromatic amino acid metabolism, highlighting these as preferential processes by which Y. pestis gene expression is modulated during flea infection.