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.

中文翻译：

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一氧化氮动态平衡是曲霉菌分生孢子的光依赖性调节所必需的。

一氧化氮（NO）可以由亚硝酸盐或精氨酸生物合成。尽管在细菌，植物和哺乳动物的许多生物过程中，NO作为信号参与其中，但对于真菌中NO的作用知之甚少。在这里，我们显示在构巢曲霉中，NO水平受环境光信号的调节。编码黄素血红蛋白的fhbB基因参与NO氧化为硝酸盐，而由agaA编码的精氨酸调节的精氨酸酶（控制细胞内精氨酸的浓度）均受光上调。光敏性诱导fhbB和agaA需要植物色素fphA，而当培养基中存在精氨酸时，白领基因lreA充当阻遏物。细胞内的精氨酸池在两个发育程序（分娩和性发育）的诱导下增加，在促进性发育的条件下，这种增加更大。低浓度的精氨酸的存在不会影响分生孢子的光依赖性调节，但是高浓度的精氨酸会超出光信号。fhbB的缺失导致精氨酸和硝酸盐介质上分生孢子的光调节部分丧失，而fhbA的缺失仅影响硝酸盐介质上分生孢子的光调节。我们的工作模型考虑了环境提示与细胞内信号之间的串扰，以调节真菌繁殖。fhbB的缺失导致精氨酸和硝酸盐介质上分生孢子的光调节部分丧失，而fhbA的缺失仅影响硝酸盐介质上分生孢子的光调节。我们的工作模型考虑了环境提示与细胞内信号之间的串扰，以调节真菌繁殖。fhbB的缺失导致精氨酸和硝酸盐介质上分生孢子的光调节部分丧失，而fhbA的缺失仅影响硝酸盐介质上分生孢子的光调节。我们的工作模型考虑了环境提示与细胞内信号之间的串扰，以调节真菌繁殖。