Characterization and regulation of the resistance-nodulation-cell division-type multidrug efflux pumps MdtABC and MdtUVW from the fire blight pathogen Erwinia amylovora.
Characterization and regulation of the resistance-nodulation-cell division-type multidrug efflux pumps MdtABC and MdtUVW from the fire blight pathogen Erwinia amylovora.
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DOI：
10.1186/1471-2180-14-185
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发表时间：
2014-07-11
期刊：
影响因子：
4.2
通讯作者：
Weingart H
中科院分区：
文献类型：
--
作者：
Pletzer D;Weingart H
革兰氏阴性细菌淀粉欧文氏杆菌是引起苹果、梨、木瓜、覆盆子和椰子等玫瑰科植物大火疫病的致病菌。为了在宿主中生存和繁殖，微生物必须能够避开抗菌植物化合物的毒性作用，如类黄酮类和单宁。淀粉菌使用多种药物外排转运体，识别并主动将有毒化合物输出到细胞外。在这里，我们鉴定了两个异三聚体抗性结瘤细胞分裂(RND)型多药外排泵，MdtABC和MdtUVW。这些RND系统的不同寻常之处在于，它们包含两种不同的RND蛋白，形成一个功能泵。为了找出两个外排系统的底物特异性，我们在一个缺乏主要RND泵AcrB的超敏突变体中过度表达了转运蛋白。这两种转运蛋白都介导了对几种黄酮类、夫西地酸和新霉素的抗性。此外，mdtABC介导了对交沙霉素、胆盐和硝酸银的抗性，mdtUVW介导了对克霉唑的抗性。缺失mdtABC和mdtUVW的突变体在苹果砧木中的繁殖能力降低。定量RT-PCR分析表明，转运蛋白基因在苹果砧木侵染过程中被诱导表达。多酚植物化合物单宁和重金属盐钨酸盐诱导mdtABC的表达。最后，mdtABC基因的表达受到BaeSR双组分系统的反应调节器Baer的调控，BaeSR是一个控制对环境变化的适应性反应的细胞膜应激反应系统。MdtABC和MdtUVW的表达是在淀粉菌生长过程中诱导的。我们鉴定了植物多酚单宁是mdtABC表达的诱导物。MdtABC和mdtUVW缺陷突变体在苹果砧木中繁殖能力的降低表明，外排泵参与了对植物抗菌剂的抗性，可能包括被鉴定为这两个泵的底物的类黄酮类化合物。此外，我们发现mdtABC操纵子属于双组分调节子Baer的调节子，这表明该RND转运蛋白在淀粉菌的细胞膜应激反应中发挥了作用。
The Gram-negative bacterium Erwinia amylovora is the causal agent of the devastating disease fire blight in rosaceous plants such as apple, pear, quince, raspberry, and cotoneaster. In order to survive and multiply in a host, microbes must be able to circumvent the toxic effects of antimicrobial plant compounds, such as flavonoids and tannins. E. amylovora uses multidrug efflux transporters that recognize and actively export toxic compounds out of the cells. Here, two heterotrimeric resistance-nodulation-cell division (RND)-type multidrug efflux pumps, MdtABC and MdtUVW, from E. amylovora were identified. These RND systems are unusual in that they contain two different RND proteins forming a functional pump. To find the substrate specificities of the two efflux systems, we overexpressed the transporters in a hypersensitive mutant lacking the major RND pump AcrB. Both transporters mediated resistance to several flavonoids, fusidic acid and novobiocin. Additionally, MdtABC mediated resistance towards josamycin, bile salts and silver nitrate, and MdtUVW towards clotrimazole. The ability of the mdtABC- and mdtUVW-deficient mutants to multiply in apple rootstock was reduced. Quantitative RT-PCR analyses revealed that the expression of the transporter genes was induced during infection of apple rootstock. The polyphenolic plant compound tannin, as well as the heavy metal salt tungstate was found to induce the expression of mdtABC. Finally, the expression of the mdtABC genes was shown to be regulated by BaeR, the response regulator of the two-component system BaeSR, a cell envelope stress response system that controls the adaptive responses to changes in the environment. The expression of MdtABC and MdtUVW is induced during growth of E. amylovora in planta. We identified the plant polyphenol tannin as inducer of mdtABC expression. The reduced ability of the mdtABC- and mdtUVW-deficient mutants to multiply in apple rootstock suggests that the efflux pumps are involved in resistance to plant antimicrobials, maybe including flavonoids, which were identified as substrates of both pumps. Furthermore, we found that the mdtABC operon belongs to the regulon of the two-component regulator BaeR suggesting a role of this RND transporter in the cell envelope stress response of E. amylovora.
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影响因子：
3.5
作者：
CHEREPANOV, PP;WACKERNAGEL, W
通讯作者：
WACKERNAGEL, W
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