Sanya Institute of Nanjing Agricultural University, Department of Microbiology, Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural Universitygrid.27871.3b, Nanjing, Jiangsu, People's Republic of China.
Microbiol Spectr. 2022 Dec 21;10(6):e0129722. doi: 10.1128/spectrum.01297-22. Epub 2022 Nov 2.
Water stress affects both the growth and development of filamentous fungi; however, the mechanisms underlying their response to water stress remain unclear. In this study, water stress was found to increase intracellular reactive oxygen species (ROS) level, ganoderic acid (GA) content, and NADPH oxidase (NOX) activity of Ganoderma lucidum by 148.45%, 75.32%, and 161.61%, respectively. Water stress induced the expression of the G. lucidum aquaporin (GlAQP) gene, which facilitated water transfer for microbial growth. Compared to wild type (WT), exposure to water stress increased growth inhibition rate, ROS level, and GA content of -silenced strains by 37 to 41%, 36 to 38%, and 25%, respectively. Furthermore, at the early stage of fermentation in -silenced strains, water stress resulted in 16 to 17% and 9 to 10% lower ROS level and GA content compared to WT, respectively. However, in -overexpressing strains, ROS level and GA content were 22 to 24% and 12 to 13% higher than in WT, respectively. In -silenced strains, water stress at the late stage resulted in 35 to 37% and 29 to 30% higher ROS level and GA content, respectively, while in -overexpressing strains, levels were 16 to 17% and 9% lower than WT, respectively. Cross talk between GlAQP and NOX positively regulated the GA biosynthesis of G. lucidum via ROS under water stress at the early stage but this regulation became negative at the late stage. This study deepens the understanding of fungal signaling transduction under water stress and provides a reference for analyzing environmental factors that influence the regulation of the fungal secondary metabolism. Ganoderma lucidum is an advanced basidiomycete that produces medicinally active secondary metabolites (especially ganoderic acid [GA]) with high commercial value. Water stress imposes an important environmental challenge to G. lucidum. The mechanism of GA biosynthesis under water stress and the role of G. lucidum aquaporin (GlAQP) during its biosynthesis remain unclear. Moreover, the effect of the relationship between GlAQP and NADPH oxidase (NOX) on the level of reactive oxygen species and GA production under water stress is unknown. This study provides information on the biological response mechanism of G. lucidum to water stress. A new theory on the cell signaling cascade of G. lucidum tolerance to water stress is provided that also incorporates the biosynthesis of secondary metabolites involved in NOX and GlAQP.
水胁迫会影响丝状真菌的生长和发育；然而，其对水胁迫响应的机制仍不清楚。本研究发现，水胁迫使灵芝细胞内活性氧（ROS）水平、灵芝酸（GA）含量和 NADPH 氧化酶（NOX）活性分别增加了 148.45%、75.32%和 161.61%。水胁迫诱导灵芝水通道蛋白（GlAQP）基因的表达，促进微生物生长的水分转移。与野生型（WT）相比，在沉默菌株中，水胁迫使生长抑制率、ROS 水平和 GA 含量分别增加了 37%至 41%、36%至 38%和 25%。此外，在沉默菌株的发酵早期，与 WT 相比，水胁迫导致 ROS 水平和 GA 含量分别降低了 16%至 17%和 9%至 10%。然而，在过表达菌株中，ROS 水平和 GA 含量分别比 WT 高 22%至 24%和 12%至 13%。在沉默菌株中，水胁迫在晚期导致 ROS 水平和 GA 含量分别增加了 35%至 37%和 29%至 30%，而过表达菌株中的水平分别比 WT 低 16%至 17%和 9%。水胁迫在早期通过 ROS 正向调节 GlAQP 和 NOX 之间的对话，从而促进灵芝 GA 生物合成，但在晚期则变为负调控。本研究加深了对丝状真菌在水胁迫下信号转导的理解，并为分析影响真菌次生代谢调控的环境因素提供了参考。灵芝是一种先进的担子菌，能产生具有高商业价值的药用活性次生代谢产物（特别是灵芝酸[GA]）。水胁迫对灵芝构成了重要的环境挑战。在水胁迫下 GA 生物合成的机制以及灵芝水通道蛋白（GlAQP）在其生物合成中的作用尚不清楚。此外，水胁迫下 GlAQP 和 NADPH 氧化酶（NOX）之间的关系对活性氧水平和 GA 产量的影响尚不清楚。本研究提供了灵芝对水胁迫的生物响应机制信息。提出了一个关于灵芝耐受水胁迫的细胞信号级联的新理论，该理论还包含了涉及 NOX 和 GlAQP 的次生代谢物生物合成。
