Arratia-Quijada Jenny, Sánchez Olivia, Scazzocchio Claudio, Aguirre Jesús
Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Eukaryot Cell. 2012 Sep;11(9):1132-42. doi: 10.1128/EC.00101-12. Epub 2012 Jul 13.
In the fungus Aspergillus nidulans, inactivation of the flbA to -E, fluG, fluF, and tmpA genes results in similar phenotypes, characterized by a delay in conidiophore and asexual spore production. flbB to -D encode transcription factors needed for proper expression of the brlA gene, which is essential for asexual development. However, recent evidence indicates that FlbB and FlbE also have nontranscriptional functions. Here we show that fluF1 is an allele of flbD which results in an R47P substitution. Amino acids C46 and R47 are highly conserved in FlbD and many other Myb proteins, and C46 has been proposed to mediate redox regulation. Comparison of ΔflbD and flbD(R47P) mutants uncovered a new and specific role for flbD during sexual development. While flbD(R47P) mutants retain partial function during conidiation, both ΔflbD and flbD(R47P) mutants are unable to develop the peridium, a specialized external tissue that differentiates during fruiting body formation and ends up surrounding the sexual spores. This function, unique among other fluffy genes, does not affect the viability of the naked ascospores produced by mutant strains. Notably, ascospore development in these mutants is still dependent on the NADPH oxidase NoxA. We generated R47K, C46D, C46S, and C46A mutant alleles and evaluated their effects on asexual and sexual development. Conidiation defects were most severe in ΔflbD mutants and stronger in R47P, C46D, and C46S strains than in R47K strains. In contrast, mutants carrying the flbD(C46A) allele exhibited conidiation defects in liquid culture only under nitrogen starvation conditions. The R47K, R47P, C46D, and C46S mutants failed to develop any peridial tissue, while the flbD(C46A) strain showed normal peridium development and increased cleistothecium formation. Our results show that FlbD regulates both asexual and sexual differentiation, suggesting that both processes require FlbD DNA binding activity and that FlbD is involved in the response to nitrogen starvation.
在真菌构巢曲霉中，flbA至-E、fluG、fluF和tmpA基因的失活会导致相似的表型，其特征是分生孢子梗和无性孢子产生延迟。flbB至-D编码brlA基因正常表达所需的转录因子，brlA基因对无性发育至关重要。然而，最近的证据表明，FlbB和FlbE也具有非转录功能。在此我们表明，fluF1是flbD的一个等位基因，导致R47P替换。氨基酸C46和R47在FlbD和许多其他Myb蛋白中高度保守，并且有人提出C46介导氧化还原调节。对ΔflbD和flbD(R47P)突变体的比较揭示了flbD在有性发育过程中的一个新的特定作用。虽然flbD(R47P)突变体在分生孢子形成过程中保留部分功能，但ΔflbD和flbD(R47P)突变体都无法发育出包被，包被是一种特殊的外部组织，在子实体形成过程中分化并最终包围有性孢子。这种在其他蓬松基因中独特的功能，并不影响突变菌株产生的裸露子囊孢子的活力。值得注意的是，这些突变体中的子囊孢子发育仍然依赖于NADPH氧化酶NoxA。我们生成了R47K、C46D、C46S和C46A突变等位基因，并评估了它们对无性和有性发育的影响。分生孢子形成缺陷在ΔflbD突变体中最为严重，在R47P、C46D和C46S菌株中比在R47K菌株中更强。相比之下，携带flbD(C46A)等位基因的突变体仅在氮饥饿条件下的液体培养中表现出分生孢子形成缺陷。R47K、R47P、C46D和C46S突变体未能发育出任何包被组织，而flbD(C46A)菌株显示出正常的包被发育和闭囊壳形成增加。我们的结果表明，FlbD调节无性和有性分化，这表明这两个过程都需要FlbD的DNA结合活性，并且FlbD参与对氮饥饿的反应。
