The chsB gene of Aspergillus nidulans is necessary for normal hyphal growth and development
The chsB gene of Aspergillus nidulans is necessary for normal hyphal growth and development
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DOI：
10.1006/fgbi.1996.0035
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发表时间：
1996-09-01
影响因子：
3
通讯作者：
Bulawa, CE
中科院分区：
文献类型：
--
作者：
Borgia, PT;Iartchouk, N;Bulawa, CE
来自线状曲霉的chsB基因编码III类几丁质合成酶，这种酶在丝状真菌中发现，但在酵母样生物中没有。利用一种新的方法，我们从杂合的二倍体突变体中分离出携带一个被破坏的chsB等位基因的单倍体分离体。单倍体干扰物生长为微小的菌落，不分生，来自干扰物的菌丝尖端增大，分枝程度高，侧壁紊乱，菌丝不缺乏几丁质含量，没有裂解的迹象，干扰物表型不被渗透稳定剂修复。结果表明，由chsb编码的酶合成的几丁质对细胞壁的刚性没有实质性的贡献，但对菌丝的正常生长和组织是必需的。这些干扰物的性质与具有破坏ch -1基因的粗神经孢子虫菌株相似，该基因也编码III类几丁质合成酶。一个含有野生型和被破坏的chsB等位基因的假丝莲异核体的形态表明，chsB在菌丝体的局部区域起作用。异核体产生的两种亲本基因型的分生孢子数量几乎相等，这表明野生型的chsB基因对分生孢子的形成不是必需的。此外，我们从密切相关的机会致病菌烟曲霉（a . fumigatus）中鉴定并测序了第二种以前未描述过的chsB同源基因。在烟曲霉中发现两个III类几丁质合成酶基因，在烟曲霉中发现一个该类基因，说明了将烟曲霉作为烟曲霉遗传模型的局限性。(C) 1996学术出版社，Inc.
The chsB gene from Aspergillus nidulans encodes a class III chitin synthase, an enzyme class found in filamentous fungi but not in yeast-like organisms. Using a novel method, we isolated haploid segregants carrying a disrupted chsB allele from heterozygous diploid disruptants. The haploid disruptants grow as minute colonies that do not conidiate, Hyphae from the disruptants have enlarged tips, a high degree of branching, and disorganized lateral walls, The mycelium is not deficient in chitin content and shows no evidence of lysis, The disruptant phenotype is not remedied by osmotic stabilizers, The results indicate that chitin synthesized by the chsB-encoded enzyme does not substantially contribute to the rigidity of the cell wall but is necessary for normal hyphal growth and organization, The properties of the A. nidulans disruptant are similar to those for Neurospora crassa strains with a disrupted chs-1 gene, which also encodes a class III chitin synthase, The morphology of an A. nidulans heterokaryon containing both the wild-type and the disrupted chsB alleles indicates that chsB acts in local areas of the mycelium. The heterokaryon produces conidia of both parental genotypes in nearly equal numbers, indicating that the wild-type chsB gene is not necessary for conidium formation, In addition, we identified and sequenced a second, previously undescribed, homolog of chsB from the closely related opportunistic pathogen, A. fumigatus. The finding of two class III chitin synthase genes in A. fumigatus and a single gene of this class in A. nidulans illustrates limitations of using A. nidulans as a genetic model for A. fumigatus. (C) 1996 Academic Press, Inc.