Characterization of the developmental regulator FlbE in Aspergillus fumigatus and Aspergillus nidulans

Several upstream developmental activators control asexual development (conidiation) in Aspergillus In this study we characterize one of such activators called flbE in Aspergillus funugatus and Aspergillus nidulans The predicted FlbE protein is composed of 222 and 201 aa in A fumigatus and A nidulans respectively While flbE is transiently expressed during early phase of growth in A nidulans It is somewhat constitutively expressed during the lifecycle of A fumigatus The deletion of flbE causes reduced conidiation and delayed expression of brlA and vosA in both species Moreover FlbE is necessary for salt-induced development in liquid submerged culture in A funugatus The A nidulans flbE null mutation is fully complemented by A fumigatus flbE indicating a functional conservancy of FlbE in Aspergillus Both the deletion and overexpression of flbE in A nidulans result in developmental defects enhanced autolysis precocious cell death and delayed expression of brlA/vosA suggesting that balanced activity of FlbE is crucial for proper growth and development Importantly the N-terminal portion of FlbE exhibits the trans-activation ability in yeast whereas the C-terminal half negatively affects its activity Site-directed mutagenesis of certain conserved N-terminal amino acids abolishes the ability of trans-activation overexpression-induced autolysis and complementing the null mutation Finally overexpression of flbD but not flbB or flbC restores conidiation in A nidulans Delta flbE generally supporting the current genetic model for developmental regulation (C) 2010 Elsevier Inc All rights reserved