Molecular Mechanism and Genetic Determinants of Buprofezin Degradation
Molecular Mechanism and Genetic Determinants of Buprofezin Degradation
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噻嗪酮降解的分子机制和遗传决定因素
DOI：
10.1128/aem.00868-17
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发表时间：
2017-09-01
影响因子：
4.4
通讯作者：
Yan, Xin
中科院分区：
文献类型：
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作者：
Chen, Xueting;Ji, Junbin;Yan, Xin
噻嗪酮是一种广泛使用的昆虫生长调节剂，其残留量在环境中频繁检出，对水生生物和非靶标昆虫构成威胁。微生物对噻嗪酮在自然环境中的降解起着重要作用。然而，相关的分解代谢途径尚未完全表征，并且catalysis的分子机制仍然完全未知。青神红球菌YL-1能够利用噻嗪酮作为唯一的碳源和能源进行生长。在这项研究中，上游分解代谢途径的菌株YL-1的鉴定使用串联质谱。噻嗪酮由苯环和杂环组成。降解由苯环的二羟基化引发，并通过脱氢、芳环裂解、酰胺键断裂和释放杂环2-叔丁基亚氨基-3-异丙基-1，3，5-噻二嗪烷-4-酮（2-BI）继续进行。分离到一株噻嗪酮降解缺陷突变株YL-0。比较基因组分析结合基因缺失和互补实验表明，基因簇bfzBA 3A 4A 1A 2C是负责噻嗪酮的上游分解代谢途径。bfzA 3A 4A 1A 2簇编码一种新的Rieske nonheme铁加氧酶（RHO）系统，该系统负责噻嗪酮在苯环上的二羟基化; bfzB参与脱氢，bfzC负责苯环裂解。此外，bfzBA 3A 4A 1A 2C的产物还可以催化联苯、黄烷酮、黄酮和联苯菊酯的二羟基化、脱氢和芳环断裂。此外，转录研究表明，bfzBA 3A 4A 1A 2C是组织在一个转录单位，是组成型表达的菌株YL-1。重要的是有一个越来越多的关注噻嗪酮的残留和环境命运。微生物代谢是噻嗪酮在自然环境中降解的重要机制。然而，噻嗪酮微生物降解的分子机制和遗传决定因素尚未得到很好的确定。本研究揭示了青神红球菌YL-1中噻嗪酮上游分解代谢途径的基因簇bfzBA 3A 4A 1A 2C。bfzBA 3A 4A 1A 2C的降解产物对联苯菊酯也有一定的降解作用。这些结果加深了对噻嗪酮微生物降解机理的认识，为菌株YL-1和bfzBA 3A 4A 1A 2C在噻嗪酮污染生物修复中的应用奠定了基础。
Buprofezin is a widely used insect growth regulator whose residue has been frequently detected in the environment, posing a threat to aquatic organisms and nontarget insects. Microorganisms play an important role in the degradation of buprofezin in the natural environment. However, the relevant catabolic pathway has not been fully characterized, and the molecular mechanism of catabolism is still completely unknown. Rhodococcus qingshengii YL-1 can utilize buprofezin as a sole source of carbon and energy for growth. In this study, the upstream catabolic pathway in strain YL-1 was identified using tandem mass spectrometry. Buprofezin is composed of a benzene ring and a heterocyclic ring. The degradation is initiated by the dihydroxylation of the benzene ring and continues via dehydrogenation, aromatic ring cleavage, breaking of an amide bond, and the release of the heterocyclic ring 2-tert-butylimino-3-isopropyl-1,3,5-thiadiazinan-4-one (2-BI). A buprofezin degradation-deficient mutant strain YL-0 was isolated. A comparative genomic analysis combined with gene deletion and complementation experiments revealed that the gene cluster bfzBA3A4A1A2C is responsible for the upstream catabolic pathway of buprofezin. The bfzA3A4A1A2 cluster encodes a novel Rieske nonheme iron oxygenase (RHO) system that is responsible for the dihydroxylation of buprofezin at the benzene ring; bfzB is involved in dehydrogenation, and bfzC is in charge of benzene ring cleavage. Furthermore, the products of bfzBA3A4A1A2C can also catalyze dihydroxylation, dehydrogenation, and aromatic ring cleavage of biphenyl, flavanone, flavone, and bifenthrin. In addition, a transcriptional study revealed that bfzBA3A4A1A2C is organized in one transcriptional unit that is constitutively expressed in strain YL-1.IMPORTANCE There is an increasing concern about the residue and environmental fate of buprofezin. Microbial metabolism is an important mechanism responsible for the buprofezin degradation in the natural environment. However, the molecular mechanism and genetic determinants of microbial degradation of buprofezin have not been well identified. This work revealed that gene cluster bfzBA3A4A1A2C is responsible for the upstream catabolic pathway of buprofezin in Rhodococcus qingshengii YL-1. The products of bfzBA3A4A1A2C could also degrade bifenthrin, a widely used pyrethroid insecticide. These findings enhance our understanding of the microbial degradation mechanism of buprofezin and benefit the application of strain YL-1 and bfzBA3A4A1A2C in the bioremediation of buprofezin contamination.