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Glutamine Synthetase Contributes to the Regulation of Growth, Conidiation, Sclerotia Development, and Resistance to Oxidative Stress in the Fungus Aspergillus flavus. Toxins (Basel) 2022; 14:toxins14120822. [PMID: 36548719 PMCID: PMC9785230 DOI: 10.3390/toxins14120822] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/12/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022] Open
Abstract
The basic biological function of glutamine synthetase (Gs) is to catalyze the conversion of ammonium and glutamate to glutamine. This synthetase also performs other biological functions. However, the roles of Gs in fungi, especially in filamentous fungi, are not fully understood. Here, we found that conditional disruption of glutamine synthetase (AflGsA) gene expression in Aspergillus flavus by using a xylose promoter leads to a complete glutamine deficiency. Supplementation of glutamine could restore the nutritional deficiency caused by AflGsA expression deficiency. Additionally, by using the xylose promoter for the downregulation of AflgsA expression, we found that AflGsA regulates spore and sclerotic development by regulating the transcriptional levels of sporulation genes abaA and brlA and the sclerotic generation genes nsdC and nsdD, respectively. In addition, AflGsA was found to maintain the balance of reactive oxygen species (ROS) and to aid in resisting oxidative stress. AflGsA is also involved in the regulation of light signals through the production of glutamine. The results also showed that the recombinant AflGsA had glutamine synthetase activity in vitro and required the assistance of metal ions. The inhibitor molecule L-α-aminoadipic acid suppressed the activity of rAflGsA in vitro and disrupted the morphogenesis of spores, sclerotia, and colonies in A. flavus. These results provide a mechanistic link between nutrition metabolism and glutamine synthetase in A. flavus and suggest a strategy for the prevention of fungal infection.
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Lv Q, Hu M, Tian L, Liu F, Wang Q, Xu M, Rao Z. Enhancing l-glutamine production in Corynebacterium glutamicum by rational metabolic engineering combined with a two-stage pH control strategy. BIORESOURCE TECHNOLOGY 2021; 341:125799. [PMID: 34425465 DOI: 10.1016/j.biortech.2021.125799] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 06/13/2023]
Abstract
l-glutamine is a semi-essential amino acid widely used in the food and pharmaceutical industries. The microbial synthesis of l-glutamine is limited by lack of effective strains with high titer and safety. First, ARTP mutagenesis combined with high-throughput screening generated an l-glutamine-producing strain of Corynebacterium glutamicum with titer of 25.7 ± 2.7 g/L. Subsequently, a series of rational metabolic approaches were used to further improve l-glutamine production, which included increasing the carbon flow to l-glutamine (proB and NCgl1221 knockout), enhancing the catalytic efficiency of the key enzyme (glnE knockout and glnA screening and overexpression) and reinforcement of ATP regeneration (ppk overexpression and RBS optimization). Finally, we proposed a two-stage pH control strategy to address the inconsistent effect of pH on cell growth and l-glutamine production. These combined strategies led to a 186.0% increase of l-glutamine titer compared to that of the initial strain, reaching 73.5 ± 3.1 g/L with a yield of 0.368 ± 0.034 g/g glucose.
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Affiliation(s)
- Qinglan Lv
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Mengkai Hu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Lingzhi Tian
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Fei Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Qing Wang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Meijuan Xu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China
| | - Zhiming Rao
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, PR China.
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