Garzia Aitor, Etxebeste Oier, Herrero-Garcia Erika, Fischer Reinhard, Espeso Eduardo A, Ugalde Unai
Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country, San Sebastian 20018 San Sebastian, Spain.
Mol Microbiol. 2009 Jan;71(1):172-84. doi: 10.1111/j.1365-2958.2008.06520.x. Epub 2008 Nov 5.
Aspergillus nidulans switches from vegetative growth to conidiation when aerial hyphae make contact with the atmosphere, or are subjected to specific environmental stress. The activation of the central conidiation pathway led by the transcription factor brlA is a critical milestone in this morphogenetic transition. A number of upstream developmental activators (UDAs), expressed in vegetative cells, are required for this process to occur in conjunction with cessation of vegetative growth. Mutants affected in these factors remain aconidial (fluffy) with low brlA expression levels (flb). In this report, we describe FlbE as a UDA containing two conserved but hitherto uncharacterized domains, which functions in close association with putative transcription factor FlbB. Both UDAs are functionally interdependent, and colocalize at the hypha tip in an actin cytoskeleton-dependent manner. Moreover, bimolecular fluorescence studies show that they physically interact in vivo. These findings add evidence in favour of the existence of a signalling complex at or near the Spitzenkörper as an important part of the machinery controlling the morphogenetic transition between vegetative growth and conidiation.
当气生菌丝与大气接触或受到特定环境胁迫时，构巢曲霉会从营养生长转变为产孢。由转录因子brlA引导的中央产孢途径的激活是这种形态发生转变的关键里程碑。许多在营养细胞中表达的上游发育激活因子（UDA）是这一过程发生以及营养生长停止所必需的。受这些因子影响的突变体仍然不产孢（蓬松状），brlA表达水平较低（flb）。在本报告中，我们将FlbE描述为一种含有两个保守但迄今未表征结构域的UDA，它与推定的转录因子FlbB密切相关地发挥作用。这两种UDA在功能上相互依赖，并以肌动蛋白细胞骨架依赖的方式共定位于菌丝顶端。此外，双分子荧光研究表明它们在体内发生物理相互作用。这些发现进一步证明了在Spitzenkörper处或其附近存在信号复合物，这是控制营养生长和产孢之间形态发生转变机制的重要组成部分。
