GDP-mannose pyrophosphorylase is essential for cell wall integrity, morphogenesis and viability of Aspergillus fumigatus
GDP-mannose pyrophosphorylase is essential for cell wall integrity, morphogenesis and viability of Aspergillus fumigatus
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DOI：
10.1099/mic.0.2008/019240-0
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发表时间：
2008-09-01
期刊：
影响因子：
2.8
通讯作者：
Jin, Cheng
中科院分区：
文献类型：
--
作者：
Jiang, Hechun;Ouyang, Haomiao;Jin, Cheng
GDP-甘露糖焦磷酸化酶（GMPP）以1-磷酸甘露糖和GTP为底物催化合成GDP-甘露糖，其是糖缀合物中甘露糖残基的前体。在酵母中，GMPP的抑制导致包括细胞溶解、细胞壁缺陷以及极化生长和细胞分离失败的表型。虽然已经在丝状真菌中分离和表征了几种GMPPs，但它们的作用的生理后果尚不清楚。在这项研究中，Afsrb 1，这是一个同源的酵母SRB 1/PSA 1/VIG 9的烟曲霉基因组中确定。在大肠杆菌中表达了Afsrb 1基因，并证实了其功能。通过用可诱导的构巢曲霉alcA启动子替换天然的Afsrb 1启动子，构建了条件失活突变株YJ-gmpp。3%葡萄糖的存在完全阻断了P-alcA-Afsrb 1的转录，对菌株YJ-gmpp具有致死作用。菌株YJ-gmpp中Afsrb 1表达的抑制导致包括菌丝溶解、细胞壁缺陷、极性维持受损和分支位点选择的表型。此外，记录了快速发芽和减少分生孢子。然而，与酵母相反，菌株YJ-gmpp保留了直接极性建立和分离的能力。我们的研究结果表明，Afsrb 1基因是必需的细胞壁的完整性，形态建成和烟曲霉的生活力。
GDP-mannose pyrophosphorylase (GMPP) catalyses the synthesis of GDP-mannose, which is the precursor for the mannose residues in glycoconjugates, using mannose 1-phosphate and GTP as substrates. Repression of GMPP in yeast leads to phenotypes including cell lysis, defective cell wall, and failure of polarized growth and cell separation. Although several GMPPs have been isolated and characterized in filamentous fungi, the physiological consequences of their actions are not clear. In this study, Afsrb1, which is a homologue of yeast SRB1/PSA1/VIG9 was identified in the Aspergillus fumigatus genome. The Afsrb1 gene was expressed in Escherichia coli, and recombinant AfSrb1 was functionally confirmed as a GMPP. By the replacement of the native Afsrb1 promoter with an inducible Aspergillus nidulans alcA promoter, the conditional inactivation mutant strain YJ-gmpp was constructed. The presence of 3% glucose completely blocked transcription of P-alcA-Afsrb1, and was lethal to strain YJ-gmpp. Repression of Afsrb1 expression in strain YJ-gmpp led to phenotypes including hyphal lysis, defective cell wall, impaired polarity maintenance, and branching site selection. Also, rapid germination and reduced conidiation were documented. However, in contrast to yeast, strain YJ-gmpp retained the ability to direct polarity establishment and septation. Our results showed that the Afsrb1 gene is essential for cell wall integrity, morphogenesis and viability of Aspergillus fumigatus.