Detalle de: Tip-to-nucleus migration dynamics of the asexual development regulator FlbB in vegetative cells

Summary In A spergillus nidulans , asexual differentiation requires the presence of the transcription factor FlbB at the cell tip and apical nuclei. Understanding the relationship between these two pools is crucial for elucidating the biochemical processes mediating conidia production. Tip‐to‐nucleus communication was demonstrated by photo‐convertible FlbB :: D endra2 visualization. Tip localization of FlbB depends on C ys382 in the C ‐terminus and the b ZIP DNA ‐binding domain in the N ‐terminus. FlbE , a critical FlbB interactor, binds the b ZIP domain. Furthermore, the absence of FlbE results in loss of tip localization but not nuclear accumulation. flb E deletion also abrogates transcriptional activity indicating that FlbB gains transcriptional competence from interactions with FlbE at the tip. Finally, a bipartite nuclear localization signal is required for nuclear localization of FlbB . Those motifs of FlbB may play various roles in the sequence of events necessary for the distribution and activation of this transcriptionally active developmental factor. The tip accumulation, FlbE ‐dependent activation, transport and nuclear import sketch out a process of relaying an environmentally triggered signal from the tip to the nuclei. As the first known instance of transcription factor‐mediated tip‐to‐nucleus communication in filamentous fungi, this provides a general framework for analyses focused on elucidating the set of molecular mechanisms coupling apical signals to transcriptional events.