模式生物粗糙脉孢菌光受体的研究进展

粗糙脉孢菌是一种重要的模式生物,在遗传调节机制、昼夜节律运行以及真菌光应答反应研究中起重要的作用.本综述主要介绍粗糙脉孢菌光受体WC-1和VVD的结构与功能,以及它们参与调节昼夜节律和光适应机制方面的研究进展.在该真菌中,所有已知的光应答反应都受蓝光调节,由光受体WC-1和VVD介导.WC-1是该真菌的转录因子,介导最初的光反应过程,产生VVD等多种光反应蛋白,而VVD通过负反馈机制抑制WC-1的转录作用.此外,vvd基因已经用于构建在哺乳动物中表达的光调节基因元件.     

A Novel Cryptochrome-Dependent Oscillator in Neurospora crassa

Several lines of evidence suggest that the circadian clock is constructed of multiple molecular feedback oscillators that function to generate robust rhythms in organisms. However, while core oscillator mechanisms driving specific behaviors are well described in several model systems, the nature of other potential circadian oscillators is not understood. Using genetic approaches in the fungus Neurospora crassa, we uncovered an oscillator mechanism that drives rhythmic spore development in the absence of the well-characterized FRQ/WCC oscillator (FWO) and in constant light, conditions under which the FWO is not functional. While this novel oscillator does not require the FWO for activity, it does require the blue-light photoreceptor CRYPTOCHROME (CRY); thus, we call it the CRY-dependent oscillator (CDO). The CDO was uncovered in a strain carrying a mutation in cog-1 (cry-dependent oscillator gate-1), has a period of ∼1 day in constant light, and is temperature-compensated. In addition, cog-1 cells lacking the circadian blue-light photoreceptor WC-1 respond to blue light, suggesting that alternate light inputs function in cog-1 mutant cells. We show that the blue-light photoreceptors VIVID and CRY compensate for each other and for WC-1 in CRY-dependent oscillator light responses, but that WC-1 is necessary for circadian light entrainment.     

The PAS protein VIVID defines a clock-associated feedback loop that represses light input, modulates gating, and regulates clock resetting

vvd, a gene regulating light responses in Neurospora, encodes a novel member of the PAS/LOV protein superfamily. VVD defines a circadian clock-associated autoregulatory feedback loop that influences light resetting, modulates circadian gating of input by connecting output and input, and regulates light adaptation. Rapidly light induced, vvd is an early repressor of light-regulated processes. Further, vvd is clock controlled; the clock gates light induction of vvd and the clock gene frq so identical signals yield greater induction in the morning. Mutation of vvd severely dampens gating, especially of frq, consistent with VVD modulating gating and phasing light-resetting responses. vvd null strains display distinct alterations in the phase-response curve to light. Thus VVD, although not part of the clock, contributes significantly to regulation within the Neurospora circadian system.