The AMP-Activated Protein Kinase (AMPK) Positively Regulates Lysine Biosynthesis Induced by Citric Acid in <i>Flammulina filiformis</i>
2023
Hao Fan | Feng Ge | Tao Wu | Yongzhi Liu | Li Tian | Yueqian Liu | Taobo Xiang | Hanshou Yu | Liang Shi | Qin He | Ang Ren | Ailiang Jiang
<i>Flammulina filiformis</i>, the most produced edible mushroom species in China, is rich in lysine. Further enhancing its lysine biosynthesis is vital for improving its quality in industrialized cultivation. Citric acid induction significantly increases both the biomass and growth rate of <i>F. filiformis</i> hyphae, as well as the lysine content. The genes encoding enzymes in the lysine biosynthesis pathway were detected under the optimal induction, revealing that the expression levels of <i>hcs</i>, <i>hac</i>, and <i>hah</i> were 2.67, 1.97, and 1.90 times greater, respectively, relative to the control, whereas no significant difference was seen for <i>hdh</i>, <i>aat</i>, <i>sr</i>, and <i>shd</i>, and the expression of <i>aar</i> decreased. Furthermore, the transcriptional levels of <i>Ampk</i>, <i>GCN2</i>, <i>GCN4</i>, and <i>TOR</i> were found significantly upregulated, with the most upregulated, <i>Ampk</i>, reaching a level 42.68 times greater than that of the control, while the phosphorylation of AMPK rose by nearly 54%. In AMPK-silencing strains under the optimal induction, however, the phosphorylation increment dropped to about 16% and the lysine content remained at the same level as in the WT. Thus, AMPK is presented as the critical intermediary in citric acid’s regulation of lysine biosynthesis in <i>F. filiformis</i>.
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