Department of Genetics, Faculty of Biology, University of Seville, Spain.
Department of Applied Genetics and Cell Biology, BOKU University of Natural Resources and Life Science, University and Research Center - Campus Tulln, Tulln - Donau, Austria.
Fungal Genet Biol. 2020 Apr;137:103337. doi: 10.1016/j.fgb.2020.103337. Epub 2020 Jan 25.
Nitric oxide (NO) can be biologically synthesized from nitrite or from arginine. Although NO is involved as a signal in many biological processes in bacteria, plants, and mammals, still little is known about the role of NO in fungi. Here we show that NO levels are regulated by light as an environmental signal in Aspergillus nidulans. The flavohaemoglobin-encoding fhbB gene involved in NO oxidation to nitrate, and the arginine-regulated arginase encoded by agaA, which controls the intracellular concentration of arginine, are both up-regulated by light. The phytochrome fphA is required for the light-dependent induction of fhbB and agaA, while the white-collar gene lreA acts as a repressor when arginine is present in the media. The intracellular arginine pools increase upon induction of both developmental programs (conidiation and sexual development), and the increase is higher under conditions promoting sexual development. The presence of low concentrations of arginine does not affect the light-dependent regulation of conidiation, but high concentrations of arginine overrun the light signal. Deletion of fhbB results in the partial loss of the light regulation of conidiation on arginine and on nitrate media, while deletion of fhbA only affects the light regulation of conidiation on nitrate media. Our working model considers a cross-talk between environmental cues and intracellular signals to regulate fungal reproduction.
一氧化氮（NO）可以由亚硝酸盐或精氨酸在生物体内合成。尽管 NO 作为信号分子参与了细菌、植物和哺乳动物中的许多生物过程，但人们对其在真菌中的作用仍知之甚少。在这里，我们表明，NO 水平受到光作为环境信号的调节，这在 Aspergillus nidulans 中是如此。参与将 NO 氧化为硝酸盐的黄素血红蛋白编码基因 fhbB，以及控制精氨酸细胞内浓度的精氨酸调节的精氨酸酶编码基因 agaA，都受到光的调控。光依赖性诱导 fhbB 和 agaA 需要光受体 phytochrome fphA，而当培养基中存在精氨酸时，white-collar 基因 lreA 作为一个抑制剂发挥作用。在诱导两种发育程序（分生孢子和有性生殖）时，细胞内精氨酸库增加，在促进有性生殖的条件下增加得更高。低浓度的精氨酸不会影响光对分生孢子形成的调控，但高浓度的精氨酸会掩盖光信号。fhbB 缺失导致光对精氨酸和硝酸盐培养基上的分生孢子形成的调控部分丧失，而 fhbA 缺失仅影响硝酸盐培养基上的光对分生孢子形成的调控。我们的工作模型认为，环境线索和细胞内信号之间存在交叉对话，以调节真菌的繁殖。
