Castiglioni Pascon R, Pizzirani-Kleiner A A, Miller B L
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83844, USA.
Mol Gen Genet. 2001 Jan;264(5):546-54. doi: 10.1007/s004380000360.
Wild-type Aspergillus nidulans conidia are uninucleate. The mutation bncA1 (binucleated conidia) was first described as a single mutation located on chromosome IV that caused formation of approximately 25% binucleate and 1% trinucleate conidia. In this study, we show that bncA1 conidia exit G1 arrest earlier than the wild type. Germlings have hyphal elements with abnormal morphology, elevated numbers of randomly distributed nuclei and an irregular septation pattern. Older hyphal elements undergo mitotic catastrophe, suggesting the nuclear division cycle of internal (nonterminal) elements is not arrested. The bncA1 mutation also causes aberrant morphogenesis of the asexual reproductive structure, the conidiophore. Metulae and phialides are elongated and have incorrect numbers of nuclei. Phialides also have internal septation that appears to delineate hyphal-like elements. Heterokaryon analysis using strains with contrasting auxotrophic markers showed that the bncA1 mutation resulted in a higher frequency of diploid and multinucleated prototrophic conidia than control heterokaryons. These results suggest that in bncA1 strains multiple nuclei can move from the conidiophore vesicle to the metulae and/or from the phialide to the conidium. The bncA1 mutant also showed hypersensitivity to the anti-microtubule drugs thiabendazole and nocodazole, which is consistent with the defects in cell cycle regulation and nuclear movement. We propose that bncA has an important role in correctly regulating both the cell division cycle and nuclear movement.
野生型构巢曲霉分生孢子是单核的。bncA1（双核分生孢子）突变最初被描述为位于第四条染色体上的单个突变，该突变导致约25%的双核和1%的三核分生孢子形成。在本研究中，我们发现bncA1分生孢子比野生型更早地退出G1期停滞。芽管具有形态异常的菌丝成分、随机分布的细胞核数量增加以及不规则的隔膜模式。较老的菌丝成分会发生有丝分裂灾难，这表明内部（非末端）成分的核分裂周期没有停滞。bncA1突变还会导致无性繁殖结构分生孢子梗的异常形态发生。小梗和产孢细胞伸长，细胞核数量不正确。产孢细胞也有内部隔膜，似乎勾勒出类似菌丝的成分。使用具有不同营养缺陷型标记的菌株进行异核体分析表明，与对照异核体相比，bncA1突变导致二倍体和多核原养型分生孢子的频率更高。这些结果表明，在bncA1菌株中，多个细胞核可以从分生孢子梗囊泡移动到小梗和/或从产孢细胞移动到分生孢子。bncA1突变体对抗微管药物噻苯咪唑和诺考达唑也表现出超敏感性，这与细胞周期调控和核移动的缺陷一致。我们提出bncA在正确调节细胞分裂周期和核移动方面具有重要作用。
