Overexpression of the saccharopine dehydrogenase gene improves lysine biosynthesis inFlammulina velutipes

Abstract

Saccharopine dehydrogenase (EC 1.5.1.7) regulates the last step of fungal lysine biosynthesis. The gene (Fvsdh) encoding saccharopine dehydrogenase was identified and cloned from the whole genome of Flammulina velutipes. The genomic DNA of Fvsdh is 1257 bp, comprising three introns and four exons. The full-length complementary DNA of Fvsdh comprises 1107 bp with a deduced amino acid sequence of 368 residues. A 1,000-bp promoter sequence containing the TATA box, CAAT box, and several putative cis-acting elements was also identified. The results of tissue expression analysis showed that the expression level of the Fvsdh gene was higher in the pileus than in the stipe whether in the elongation or maturation stage. Further research showed that the lysine contents were 3.03 and 2.95 mg/g in maturation-pileus and elongation-pileus, respectively. In contrast, the lysine contents were 2.49 and 2.07 mg/g in elongation-stipe and maturation-stipe, respectively. To study the function of Fvsdh, we overexpressed Fvsdh in F. velutipes and found that Fvsdh gene expression was increased from 1.1-to 3-fold in randomly selected transgenic strains. The lysine contents were also increased from 1.12-to 1.3-fold in these five transformants, except for strain T3, in which the lysine contents were the same as the control. These results indicate that the expression of the Fvsdh gene can affect the lysine content of F. velutipes. K E Y W O R D SFlammulina velutipes, lysine content, saccharopine dehydrogenase

Spermidine Synthase and Saccharopine Reductase Have Co-Expression Patterns Both in Basidiomycetes with Fusion Form and Ascomycetes with Separate Form

“…The N-terminal polyamine biosynthesis domain is exactly the spermidine synthase tetramerization domain (IPR035246). The C-terminal saccharopine dehydrogenase domain includes the saccharopine dehydrogenase NADP binding domain (IPR005097) and the saccharopine dehydrogenase C-terminal domain (IPR032095), and it acts as saccharopine reductase in the penultimate step of the lysine biosynthesis pathway named by Liu et al [ 26 ] in F. filiformis . It means that gene2942 is a natural chimeric protein of spermidine synthase (SPDS) and saccharopine reductase (SR), named FfSPDS-SR. Additionally, its fourth exon, as the longest one (1433 bp) in which no termination codon appeared, acts as a bridge between Spds and Sr to form a natural fusion gene.…”

The AMP-Activated Protein Kinase (AMPK) Positively Regulates Lysine Biosynthesis Induced by Citric Acid in Flammulina filiformis

“…Lysine production was 63% higher in mutant ECRS-gltA and 38% higher in mutant BSRS-gltA, indicating a higher metabolic flux into the lysine biosynthesis pathway. Liu et al overexpressed the gene Fvsdh encoding saccharopine dehydrogenase in F. filiformis , which increased the gene expression level by 1.1–3-fold and the lysine content in the transformants by 1.12–1.3-fold [ 33 ]. This work found that lysine content increased by nearly 13% under optimal citric acid induction conditions, with the gene expression levels of hcs , hac, and hah being 2.67, 1.97, and 1.90 times higher than the control, respectively.…”

Effects of exogenous selenium application on nutritional quality and metabolomic characteristics of mung bean (Vigna radiata L.)

“…Lysine is a limiting amino acid and one of the essential amino acids necessary for the normal growth and development of the human. However, human and animal bodies cannot synthesize lysine ( Liu et al, 2019 ). Therefore, mung bean is of great significance for the synthesis of lysine after Se application.…”