Etxebeste Oier, Herrero-García Erika, Araújo-Bazán Lidia, Rodríguez-Urra Ana B, Garzia Aitor, Ugalde Unai, Espeso Eduardo A
CIC Nanogune, San Sebastian, Spain.
Mol Microbiol. 2009 Sep;73(5):775-89. doi: 10.1111/j.1365-2958.2009.06804.x. Epub 2009 Jul 28.
Conidiophore formation in Aspergillus nidulans involves a developmental programme in which vegetative hyphae give rise to an ordered succession of differentiated cells: foot cell, stalk, vesicle, metulae, phialides and conidia. The developmental transition requires factors that are expressed in vegetative hyphae that activate the expression of the main regulator of conidiation, BrlA. One such element is the bZIP-type transcription factor FlbB. We found that flbB(-) mutants show defective branching patterns and are susceptible to autolysis under high sorbitol or sucrose concentrations, revealing a role in vegetative growth. In addition, FlbB plays a role in conidiophore initiation, as its upregulation reduces conidiophore vesicle swelling and generates a reduced number of metulae. FlbB was located at the tip of growing metulae, following a similar pattern as described in vegetative hyphae. In wild-type strains, the transition from metulae to phialides could be reversed to generate vegetative hyphae, indicating the existence of a specific control point at this stage of conidiophore formation. The combined evidence points to FlbB as a key factor in the transition to asexual development, playing a role at various control points in which the process could be reversed.
构巢曲霉中的分生孢子梗形成涉及一个发育程序，其中营养菌丝产生一系列有序分化的细胞：基细胞、梗、囊泡、小梗、产孢细胞和分生孢子。发育转变需要在营养菌丝中表达的因子，这些因子激活分生孢子形成的主要调节因子BrlA的表达。其中一个这样的元件是bZIP型转录因子FlbB。我们发现flbB(-)突变体表现出分支模式缺陷，并且在高山梨醇或蔗糖浓度下易自溶，这揭示了其在营养生长中的作用。此外，FlbB在分生孢子梗起始中起作用，因为其上调减少了分生孢子梗囊泡肿胀并产生数量减少的小梗。FlbB位于生长中的小梗尖端，遵循与营养菌丝中描述的类似模式。在野生型菌株中，从小梗到产孢细胞的转变可以逆转以产生营养菌丝，这表明在分生孢子梗形成的这个阶段存在一个特定的控制点。综合证据表明FlbB是向无性发育转变的关键因素，在该过程可以逆转的各个控制点发挥作用。
