Figure 8.

Model of a hierarchical light-sensing cascade in Neurospora crassa. Our results reveal an ordered sequence of molecular events resulting in light-regulated gene expression in Neurospora. The induction of early light responses is controlled primarily by WCC through direct binding to the ELRE on the promoter of ELRGs, including vvd, wc-1 and sub-1. In turn, SUB-1 is required for efficient transduction of light signals to some ELRGs and most LLRGs. Meanwhile, in contrast to the ELRE, a novel LLRE is shown to be required for the full induction of late light responses in vivo. In addition to the modulation of induction amplitude by the clock protein FRQ, both ELRGs and LLRGs in constant light are subject to the repression mediated by VVD. Intriguingly, some residual light responses can still be observed in the absence of WC-1. Components capable of sensing light directly through a chromophore are marked with dashed lines in the figure.