STUAP IS A SEQUENCE-SPECIFIC TRANSCRIPTION FACTOR THAT REGULATES DEVELOPMENTAL COMPLEXITY IN ASPERGILLUS-NIDULANS

The Aspergillus nidulans Stunted protein (StuAp) regulates multicellul ar complexity during asexual reproduction by moderating the core devel opmental program that directs differentiation of uninucleate, terminal ly differentiated spores from multinucleate, vegetative hyphae, StuAp is also required for ascosporogenesis and multicellular development du ring sexual reproduction, StuAp is a member of a family of fungal tran scription factors that regulate development or cell cycle progression, Further, StuAp characterizes a sub-family possessing the conserved AP SES domain, We demonstrate for the first time that the APSES domain is a sequence-specific DNA-binding domain that can be modeled as a basic helix-loop-helix (bHLH)-like structure, We have found that StuAp resp onse elements (A/T CGCG T/A N A/C) are located upstream of both critic al developmental regulatory genes and cell cycle genes in A,nidulans, StuAp is shown to act as a transcriptional repressor in A.nidulans, bu t as a weak activator in budding yeast, Our data suggest that the diff erentiation of pseudohyphal-like sterigmatal cells during multicellula r conidiophore development requires correct StuAp-regulated expression of both developmental and cell cycle genes in A.nidulans, The budding pattern of sterigmata may involve processes related to those controll ing pseudohyphal growth in budding yeast.