In filamentous fungi Light-Oxygen-Voltage (LOV) domain containing photoreceptors dictate adaptive responses to increasing levels of blue light.  Models in Neurospora crassa indicate that two LOV proteins Vivid (VVD) and White-Collar-1 (WC1) facilitate photoadaptation via blue-light induced regulation of protein stability and competitive dimer formation. Fungal species of agricultural and biotechnological importance retain homologous proteins, however biological data indicates that deviations in signaling mechanisms may exist.  Further, recent biophysical studies of VVD indicate that light-induced conformational changes important to signaling may be more complex than indicated in light-state crystal structures.  Herein, we report the crystal structure of ENVOY (ENV1), a VVD homolog in the biotechnologically important fungi <i>Trichoderma reesei</i>.  Structural and solution studies of ENV1 demonstrate that homologous proteins that retain sequence homology may not retain signal transduction mechanisms.  Rather, environmental factors and subtle alteration of signaling networks may induce unique mechanisms to allow adaptation to environmental stresses.  Specifically, a two residue shift in the position of a key Cys residue and the presence of a unique H-bond within the LOV active site alters the signal transduction landscape.  Conformational heterogeneity in key signaling motifs reconcile solution HX and light-state crystals structures of VVD and suggest a global conformational response where light alters protein dynamics.  Further, key residue substitutions promote dark state function and sensitivity to oxidative and metabolic stress. In this manner, we have identified an oxidative-stress dependent signaling mechanism, conserved in fungal plant pathogens, that may couple metabolic sensing and blue-light responses not previously identified in LOV proteins.

Structural biochemistry of a fungal LOV domain photoreceptor reveals an evolutionarily conserved pathway integrating blue-light and oxidative stress

249th National Meeting (2015)

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