DIVERSE PROGRAMS OF ASCUS DEVELOPMENT IN PSEUDOHOMOTHALLIC SPECIES OF NEUROSPORA, GELASINOSPORA, AND PODOSPORA
DIVERSE PROGRAMS OF ASCUS DEVELOPMENT IN PSEUDOHOMOTHALLIC SPECIES OF NEUROSPORA, GELASINOSPORA, AND PODOSPORA
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DOI：
10.1002/dvg.1020150111
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发表时间：
1994-01-01
期刊：
影响因子：
--
通讯作者：
PERKINS, DD
中科院分区：
文献类型：
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作者：
RAJU, NB;PERKINS, DD
对四孢子囊菌的减数分裂和子囊孢子的发育进行了重新研究，突出了不同属中四个孢子独立起源的差异。在这些物种中，就像在异源的八个孢子的粗面核菌中一样，单倍体核的融合之后直接伴随着减数分裂和减数分裂后的有丝分裂。这些分裂发生在单个未分离的巨细胞子囊内，子囊在核被子囊孢子壁包围之前达到0.1毫米的长度。两种基本不同的方式使得相反的交配型核进入不同属的四个子囊孢子。在四种不育系中，交配型基因与着丝粒紧密连锁。因此，交配型在第一次减数分裂时分离。四种核型的第二分裂纺锤体重叠且通常彼此平行，这与粗种核型的纺锤体串联排列形成对比。结果是，相对交配型的非姊妹核紧密排列在每个半子囊中，每个子囊孢子内包有一对。而在豆科和胶孢属中，二次分裂纺锤体是串联的，在每个半子囊中，相反交配型的姐妹核成对结合。这是对鹅绒委陵菜建立的，并推断对四孢子菌和四精子菌来说，交配型-着丝粒间隔几乎总是发生一次正反交，确保交配型在第二次减数分裂时分离，相反交配型的核被包围在每个子囊孢子中。也可以看到其他不太根本的差异。四精脉孢霉的染色体取向和纺锤体极体斑块在间期II与其他物种不同。第三分裂纺锤体在青霉属中平行于子囊壁，而在孢子门和脉孢霉中则横跨子囊壁。在幼子囊孢子有丝分裂后，这两种孢子在核行为上有所不同。在四孢子疫霉菌中，四个核中的两个迁移到尾细胞，尾细胞退化，每种交配型留下一个功能核。相比之下，在鹅绒委陵菜中，四个核中只有一个进入尾细胞，使萌发的子囊孢子具有两个交配型和另一个交配型的功能核。假均质条件及其异核营养阶段对单个有机体和繁殖系统都有重大影响。发育和重组的基因控制是复杂的。近亲交配不是强制性的。(C)1994年Wiley-Liss，Inc.
Meiosis and ascospore development in the four-spored pseudohomothallic ascomycetes Neurospora tetrasperma, Gelasinospora tetrasperma, Podospora anserina, and P. tetraspora have been reexamined, highlighting differences that reflect independent origins of the four-spored condition in the different genera. In these species, as in the heterothallic eight-spored N. crassa, fusion of haploid nuclei is followed directly by meiosis and a postmeiotic mitosis. These divisions take place within a single unpartitioned giant cell, the ascus, which attains a length of >0.1 mm before nuclei are enclosed by ascospore walls. Two basically different modes underlie the delivery of opposite mating type nuclei into each of the four ascospores in the different genera. In N. tetrasperma on the one hand, the mating type locus is closely centromere-linked. Mating types therefore segregate at the first meiotic division. The second-division spindles of N. tetrasperma overlap and are usually parallel to one another, in contrast to the their tandem arrangement in N. crassa. As a result, nonsister nuclei of opposite mating type are placed close together in each half-ascus and a pair is enclosed in each ascospore. In the Podospora and Gelasinospora species on the other hand, the second-division spindles are in tandem, with sister nuclei of opposite mating type associated as a pair in each half-ascus. It is established for P. anserina and inferred for P. tetraspora and G. tetrasperma that a single reciprocal crossing over almost always occurs in the mating type-centromere interval, ensuring that mating types segregate at the second meiotic division and that nuclei of opposite mating type are enclosed in each ascospore.Other differences are also seen that are less fundamental. Neurospora tetrasperma differs from the other species in the orientation of chromosomes and spindle pole body plaques at interphase II. Third-division spindles are oriented parallel to the ascus wall in Gelasinospora but across the ascus in Podospora and Neurospora. The two Podospora species differ from one another in nuclear behavior following mitosis in the young ascospores. In P. tetraspora, two of the four nuclei migrate into the tail cell, which degenerates, leaving one functional nucleus of each mating type. In P. anserina, by contrast, only one of the four nuclei moves into the tail cell, leaving the germinating ascospore with two functional nuclei of one mating type and one of the other.The pseudohomothallic condition with its heterokaryotic vegetative phase has significant consequences for both the individual organism and the breeding system. Genetic controls of development and recombination are complex. Inbreeding is not obligatory. (C) 1994 Wiley-liss, Inc.