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J Microbiol. 2019 May 11. doi: 10.1007/s12275-019-9123-6. [Epub ahead of print]

FgIlv3a is crucial in branched-chain amino acid biosynthesis, vegetative differentiation, and virulence in Fusarium graminearum.

Liu X1,2, Jiang Y1,3, Zhang Y1,4, Yu M1, Jiang H1,5, Xu J1,2, Shi J6,7.

Author information

1
Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology/Key Laboratory for Control Technology and Standard for Agro-product Safety and Quality, Ministry of Agriculture and Rural Affairs/Key Laboratory for Agro-product Safety Risk Evaluation (Nanjing), Ministry of Agriculture and Rural Affairs/Collaborative Innovation Center for Modern Grain Circulation and Safety/Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, Jiangsu, P. R. China.
2
School of Food and Biological Engineering, Jiangsu Univeristy, Zhenjiang, 212013, Jiangsu, P. R. China.
3
College of Food Science, Tibet Agriculture and Animal Husbandry University, Linzhi, 860000, Tibet, P. R. China.
4
College of Life Science, Sanquan College of Xinxiang Medical University, Xinxiang, 453003, Henan, P. R. China.
5
College of Plant Protection, Nanjing Agriculture University, Nanjing, 210095, Jiangsu, P. R. China.
6
Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology/Key Laboratory for Control Technology and Standard for Agro-product Safety and Quality, Ministry of Agriculture and Rural Affairs/Key Laboratory for Agro-product Safety Risk Evaluation (Nanjing), Ministry of Agriculture and Rural Affairs/Collaborative Innovation Center for Modern Grain Circulation and Safety/Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, Jiangsu, P. R. China. shiji@jaas.ac.cn.
7
School of Food and Biological Engineering, Jiangsu Univeristy, Zhenjiang, 212013, Jiangsu, P. R. China. shiji@jaas.ac.cn.

Abstract

Dihydroxyacid dehydratase (DHAD), encoded by ILV3, catalyses the third step in the biosynthetic pathway of branched-chain amino acids (BCAAs), which include isoleucine (Ile), leucine (Leu), and valine (Val). Enzymes involved in BCAA biosynthesis exist in bacteria, plants, and fungi but not in mammals and are therefore attractive targets for antimicrobial or herbicide development. In this study, three paralogous ILV3 genes (FgILV3A, FgILV3B, and FgILV3C) were identified in the genome of Fusarium graminearum, the causal agent of Fusarium head blight (FHB). Deletion of FgILV3A alone or combined with FgILV3B or FgILV3C indicated an important role for FgILV3A in BCAA biosynthesis. FgILV3A deletion mutants lost the ability to grow on medium lacking amino acids. Exogenous supplementation of 1 mM Ile and Val rescued the auxotrophy of ΔFgIlv3A, though 5 mM was required to recover the growth defects in ΔFgIlv3AB and ΔFgIlv3AC strains, indicating that FgIlv3b and FgIlv3c exhibit redundant but accessory roles with FgIlv3a in BCAA biosynthesis. The auxotrophy of ΔFgIlv3A resulted in pleiotropic defects in aerial hyphal growth, in conidial formation and germination, and in aurofusarin accumulation. In addition, the mutants showed reduced virulence and deoxynivalenol production. Overall, our study demonstrates that FgIlv3a is crucial for BCAA biosynthesis in F. graminearum and a candidate fungicide target for FHB management.

KEYWORDS:

Fusarium graminearum; branched-chain amino acid biosynthesis; dihydroxyacid dehydratase; paralogous FgILV3 genes; virulence

PMID:
31079334
DOI:
10.1007/s12275-019-9123-6

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