A transcription factor GCN4 contributes to maintaining intracellular amino acid contents under the nitrogen limiting conditions in mushroom Ganoderma lucidum

Abstract

Abstract Background Edible mushrooms, with their delightful taste and abundant protein and amino acids required by human, can be used as substitutes of meat or plant proteins in a variety of foods and beverages. Nitrogen limiting conditions promote the development of fruiting bodies in mushrooms, but are not conducive to the accumulation of amino acids. Previous study has revealed that GCN4 has a pivotal role in response to nitrogen limiting conditions in Ganoderma lucidum. But its influence on amino acid contents is nearly unknown. Results In this study, we found that the amino acid contents reached 120.51 mg per gram of mycelia in the WT strain under the 60 mM asparagine condition, but decreased by 62.96% under the 3 mM asparagine condition. Second, silencing of gcn4 resulted in a 54.2% decrease of amino acid contents under the 60 mM asparagine condition, especially for the essential and monosodium glutamate-like taste amino acids. However, these were more pronounced under the 3 mM asparagine condition. Third, silencing of gcn4 markedly inhibited the expression of amino acid biosynthesis and transporting genes. In addition, GCN4 enhanced the tricarboxylic acid cycle (TCA) and glycolytic pathway, and inhibited the activity of target of rapamycin complex 1 (TORC1), thus being beneficial for maintaining amino acid homeostasis. Conclusion This study confirmed that GCN4 contributed to maintaining the amino acid contents in mushrooms under the low concentration of nitrogen. In conclusion, our study provides a research basis for GCN4 to regulate amino acid synthesis and improve nutrition of edible mushrooms.