Light regulation of differentiation through a red- and blue-light sensing light regulator complex in Aspergillus nidulans

光敏色素通过两种稳定构象之间的光相互转换来感知红光和远红光。它们最初被认为局限于光合生物，但最近在异养真细菌和真菌中发现了它们，而对它们的功能知之甚少。有趣的是，丝状真菌的发育程序是由红光和远红光触发的，因此该系统使人想起光敏色素反应。我们发现一种假定的光敏色素PhsA在这种反应中起着至关重要的作用。PhsA还与原核生物的双组分调控系统具有同源性，具有组氨酸激酶和响应调节受体结构域。PhsA将从大肠杆菌和假芽孢杆菌中表达和纯化，以表征其发色团和激酶活性。为了揭示信号级联，我们将研究两个先前表征的Zn(II)2Cys6转录因子RosA（性发育抑制因子）和NosA（无性发育因子），光调节因子VeA和信号小体成分作为PhsA的潜在靶点。它们的活性或亚细胞定位可能取决于ph。这将是第一个在植物和细菌王国之外被表征的光敏色素。

Phytochromes sense red and far-red light through photo-interconversion between two stable conformations. They were originally thought to be confined to photosynthetic organisms but were recently discovered in heterotrophic eubacteria and in fungi where little is known about their functions. Interestingly, the developmental programs of the filamentous fungus Aspergillus nidulans are triggered by red and far-red light, and the system is thus reminiscent of the phytochrome response. We discovered a crucial role of a putative phytochrome, PhsA, for this response. PhsA shares also homology to prokaryotic twocomponent regulatory systems with a histidine kinase and a response regulator receiver domain. PhsA will be expressed and purified from E. coli and A. nidulans to characterize its chromophore and kinase activity. To unravel the signalling cascade, we are going to study the two previously characterized Zn(II)2Cys6 transcription factors RosA (repressor of sexual development) and NosA (no sexual development), the light regulator VeA and signalosome components as potential targets of PhsA. Their activity or subcellular localization may depend on PhsA. This will be the first phytochrome characterized outside the plant and bacterial kingdoms.