Two FgLEU2 Genes with Different Roles in Leucine Biosynthesis and Infection-Related Morphogenesis in Fusarium graminearum

Abstract

3-isopropylmalate dehydrogenase (IPMD) encoded by LEU2 is a key enzyme in leucine (Leu) biosynthetic pathway. Analysis of the genome sequence of Fusarium graminearum revealed two paralogous LEU2 genes (designated as FgLEU2A and FgLEU2B) in this fungus and the deduced amino acid sequences of FgLeu2A and FgLeu2B share 45% identity. Targeted disruption of individual FgLEU2A/B gene in F. graminearum assigned a more crucial role of FgLeu2A in Leu biosynthesis as disruption of FgLEU2A resulted in mutant (ΔFgLeu2A-10) that was Leu-auxotrophic and could not grow in minimal medium limited for amino acids, whereas FgLEU2B deletion mutant ΔFgLeu2B-2 was morphologically indistinguishable from the wild type strain PH-1. The growth defects of ΔFgLeu2A-10 could be overcome by exogenous addition of Leu at 0.25 mM. Double deletion of FgLEU2A and FgLEU2B (ΔFgLeu2AB-8) caused a more severe Leu-auxotrophic phenotype as the concentration of Leu exogenously added to medium to rescue the growth defect of ΔFgLeu2AB-8 should be raised to 1.25 mM, indicating a less important but nonnegligible role of FgLeu2B in Leu biosynthesis. Disturb of Leu biosynthesis caused by FgLEU2A deletion leads to slower growth rate, reduced aerial hyphal formation and red pigmentation on PDA plates and completely blocked conidial production and germination. All of the defects above could be overcome by Leu addition or complementation of the full-length FgLEU2A gene. ΔFgLeu2A-10 also showed significantly increased sensitivity to osmotic and oxidative stresses. Pathogenicity assay results showed that virulence of mutants lacking FgLEU2A were dramatically impaired on wheat heads and non-host cherry tomatoes. Additionally, a low level of deoxynivalenol (DON) production of ΔFgLeu2A-10 and ΔFgLeu2AB-8 in wheat kernels was also detected. Taken together, results of this study indicated a crucial role of FgLeu2A and a less important role of FgLeu2B in Leu biosynthesis and fungal infection-related morphogenesis in F. graminearum and FgLeu2A may serve as a potential target for novel antifungal development.

2-Methoxy-1,4-naphthoquinone Induces Metabolic Shifts in Penicillium Digitatum Revealed by High-Dimensional Biological Data

“…37 The reduction of leucine may be responsible for the regulation of some genes and proteins, for example, 2-isopropylmalate synthase (IPMS) and 3-isopropylmalate dehydrogenase (IPMD) that are generally inhibited by leucine. 38 IPMS and IPMD are the critical enzymes in leucine biosynthesis that catalyze the formation of 2-isopropylmalate from acetyl-CoA and 2-oxoisovalerate. 39 IPMS and IPMD did not change significantly at the gene level, indicating that the up-regulation of these two proteins was caused by the decrease of leucine.…”

“…Leucine is not only a regulator of protein synthesis but also plays a vital role in regulating the signal transduction of the initiation of translation . The reduction of leucine may be responsible for the regulation of some genes and proteins, for example, 2-isopropylmalate synthase (IPMS) and 3-isopropylmalate dehydrogenase (IPMD) that are generally inhibited by leucine . IPMS and IPMD are the critical enzymes in leucine biosynthesis that catalyze the formation of 2-isopropylmalate from acetyl-CoA and 2-oxoisovalerate .…”

The Intermediates in Branched-Chain Amino Acid Biosynthesis Are Indispensable for Conidial Germination of the Insect-Pathogenic Fungus Metarhizium robertsii

“…Studies of ketol-acid reductoisomerase ILV5 (10) and dihydroxy-acid dehydratase ILV3 (11) showed that they are crucial for BCAA biosynthesis, deoxynivalenol production, and full virulence of F. graminearum. Moreover, isopropylmalate dehydrogenase LEU2 (12) and isopropylmalate isomerase LEU1 (13), which catalyze the first two reactions of Leu biosynthesis, are both essential for fungal vegetative growth, conidiogenesis, and pathogenicity.…”

MoLEU1 , MoLEU2 , and MoLEU4 regulated by MoLEU3 are involved in leucine biosynthesis, fungal development, and pathogenicity in Magnaporthe oryzae

“…FgLeu2A is crucial for leucine biosynthesis and fungal infection‐related morphogenesis. In contrast, a less important role of FgLeu2B in F. graminearum (Liu et al ., ). These indicated that further investigation need to be explored to study the functions of duplicated genes.…”