哺乳动物卵母细胞纺锤体的形成及纺锤体检验点的作用机制

染色体精确分离是在纺锤体的正确组装和纺锤体检查点(spindle assembly checkpoint,SAC)的监控下完成的,对于哺乳动物卵母细胞来说,纺锤体的形成和SAC都是保证染色体精确分离的重要因素,如果染色体分离错误将直接导致自发性流产或其他出生缺陷。卵母细胞中心体缺失后,细胞依然能够依靠独立于中心体而围绕染色体成核的微管反向平行排列能形成双极纺锤体,即自我组装纺锤体。由微观组织中心(microtubue organizing center,MTOC)召集微管聚集,成熟促进因子(maturation promoting factor,MPF)维持两次减数分裂过程中纺锤体的形成过程,细胞静止因子(cytostatic factor,CSF)维持分裂中期结构,使纺锤体在染色体没有全部集合到赤道板时保持稳定。大体积的卵母细胞容易产生非整倍体,且卵母细胞中不含有中心体这一特殊性导致卵母细胞中是否存在SAC在很长一段时间内存在争议,但现在SAC是确保卵母细胞染色体精确分离的机制之一已被初步证明。在减数分裂中期染色体之间存在一种黏连,细胞会产生"等待-后期"信号抑制SAC活性,从而保持这种黏连稳定,直至所有染色体完成与纺锤体的连接,"等待-后期"信号失活,SAC启动,使染色体间的黏连失活,进而在纺锤体的作用下染色体分离。作者综述了减数分裂过程中纺锤体的特异性组装过程和纺锤体检查点的组成及作用机制,丰富了减数分裂的相关知识,并为减数分裂过程中非整倍体的形成机制提供依据。     

水稻端四体的分子细胞学鉴定及染色体行为分析

在水稻品种中籼3037第9染色体短臂端三体的自交后代中发现了一个变异株。该植株叶片内卷,株型偏散,结实率差。分子细胞学鉴定表明,该植株体细胞染色体数比正常植株多2条,多出的染色体均比较小。进一步用来源于水稻着丝粒特异DNA序列（RCS2）以及位于水稻第9染色体短臂上的特异性DNA序列为探针,进行荧光原位杂交分析,证明该变异株多出的染色体均为第9染色体短臂,故该变异株为第9染色体短臂端四体。对变异株的减数分裂染色体行为进行分析表明,在所观察的25个细胞中,96%的细胞增加的两个端着丝粒染色体可配对形成二价体,一般不与正常的第9染色体配对形成多价体。但额外染色体形成的二价体在中期Ⅰ容易发生提前解离的现象。     

四倍体葡萄花粉母细胞减数分裂与坐果率关系的研究

以二倍体玫瑰香葡萄为对照,观察了诱变成功的２个四倍体玫瑰香葡萄品系四玫Ⅰ、四玫Ⅱ以及当前生产栽培的四倍体品种巨峰的花粉母细胞减数分裂过程;研究了四倍体葡萄花粉母细胞减数分裂过程中的种种异常现象,并探讨了这些现象与坐果率之间的关系。结果表明：四倍体葡萄花粉母细胞减数分裂过程中,后期Ⅰ、后期Ⅱ出现落后染色体的细胞频率及末期多分孢子与坐果率之间有显著的负相关关系。     

航天诱导的凤仙花突变株性状及减数分裂过程的研究

本文报道了种子经神舟 4号飞船搭载的凤仙花突变植株的性状及减数分裂过程的变化。该突变株在花色及花型等宏观性状上有很大变异。观察减数分裂过程 ,发现其小孢子母细胞减数第 1次分裂前期基本正常 ,但到后期Ⅰ出现染色体分配的严重不均 ,并出现落后染色体、分散染色体等。减数第 2次分裂完成时 ,多数形成 4分孢子 ,但同时也出现各种形式的多分孢子。小孢子中染色体数目从 1～ 2 1条不等 ,甚至多达 30多条。小孢子的形状和大小变异明显 ,且小孢子的大小与所含染色体的数目呈正相关。碘液染色检查发现绝大多数花粉不育 ,并与该突变株的低结实率一致。分析认为花粉的大小差异和花粉的育性与减数分裂异常有关 ,而这些现象都是航天诱变造成的     

百合三倍体种间杂种花粉母细胞减数分裂行为观察

对细叶百合(2x)×布鲁拉诺(4x)的三倍体种间杂种花粉母细胞减数分裂过程进行了观察,发现三倍体种间杂种减数分裂过程中出现较多异常现象,在双线期出现不等二价体;在后期I和末期工出现染色体桥;在后期Ⅰ、末期Ⅰ、中期Ⅱ和末期Ⅱ出现滞后染色体;在末期Ⅰ和二分体时期出现微核;在末期Ⅰ和后期Ⅱ出现不均等分离等.花粉母细胞减数分裂异常可能是导致花粉败育的主要原因.     

1个新油菜核不育系败育机理研究

[目的]研究1个新油菜核不育品系的败育机理。[方法]油菜现蕾后,取核不育系和可育系油菜花朵进行花器观察与比较,并用光学显微镜和电子显微镜对其花药发育进行显微和超微结构观察与比较。[结果]花器观察表明,油菜核不育系不育株的株型、株高等特征以及花器结构与正常株无显著差别,花药前期发育正常,后期逐渐萎缩败育,雌蕊发育正常。显微观察表明,核不育系的败育时期在花粉母细胞阶段,表现为花粉母细胞空泡化、细胞分裂的同步化丧失、细胞解体。超微结构显示,花粉母细胞的败育始于花粉母细胞分化期,细胞内出现许多自噬体和多泡体,并最终导致细胞解体。[结论]该核不育系的胞间通讯能力显著低于正常油菜,可能是导致其细胞分裂同步化丧失的原因。     

Production and meiotic pairing of intergeneric hybrids of Triticum × Dasypyrum species

Summary Crossing experiments between Dasypyrum villosum (2 x) and 14 taxa of Triticum sensu lato (seven diploids, five tetraploids and two hexoploids) were performed. Adult hybrids were obtained in all but three of the combinations with diploid species. A haploid plant was obtained from the combination T. aestivum x D. villosum. Cytogenetic data on the meiotic pairing in the intergeneric hybrids revealed that, in general, very little pairing occurred between the V genome of Dasypyrum and the different genomes in Triticum. There may be comparatively large differences in pairing behaviour in hybrids including different parental accessions, which shows that the Triticum as well as the Dasypyrum genotypes may influence the pairing. The combination T. aestivum x D. hordeaceum (4 x) was also produced and from the meiotic pairing in the hybrid it is evident that D. hordeaceum is an autoploid.     

Genetic male sterility in the pea (Pisum sativum L.)

Summary Genetic male sterility has been described in the pea (Pisum sativum L.), but no comprehensive effort has been made to study the phenomenon. A preceding companion paper reported the inheritance, allelism and linkage relations of thirteen male sterile mutants obtained from seed mutagen treatments. In the present study, the same male sterile mutants were investigated cytologically to determine the cause of sterility. Normal microsporogenesis and microgametogenesis was compared to that of the mutants. The ms-2, ms-3, and ms-4 mutants exhibited meiotic abnormalities similar to those described by Gottschalk and colleagues except that ms-3 had a high degree of female sterility. Chromosome clumping and spindle abnormalities leading to formation of coenocytic microspores and degeneration were characteristic of ms-2 and ms-4. The ms-2 and ms-4 mutants were previously found to be allelic, and were nearly identical cytologically in the present study. The ms-3 mutant exhibited a lack of chromosome condensation in meiosis I, and a lack of spindle formation in both meiotic divisions. Two mutations (ms-6 and ms-10) affected meiosis, with univalents at metaphase, and asynchronous divisions during meiosis II. Microspores of ms-6 completely degenerated whereas those of ms-10 showed some development. Sticky chromosomes, bridges and fragments, tripolar spindles, and lack of a second division were characteristic of ms-10. The ms-10 mutant also showed reduced female fertility. Two male steriles (ms-5 and ms-9) had abnormalities associated with premature degeneration of the tapetum. Three others (ms-7, ms-8, and ms-11) aborted pollen during meicrogametogenesis. Pollen grains of ms-11 had thinner walls than normal and lacked sculptured exine. The ms-10 mutant, and those affecting microgametogenesis (ms-5, ms-7, ms-8, ms-9, and ms-11) produced some stainable and viable pollen.     

Interspecific hybrid of Helianthus annuus × H. simulans: Characterization and utilization in improvement of cultivated sunflower (H. annuus L.)

The first success at interspecific hybridization between cultivated sunflower(H. annuus) and a diploid perennial species, H. simulans is reported. The F₁s from both direct and reciprocal directions exhibited dominance of the wild species phenotype and were pollen sterile. Meiosis was irregular in the F₁ hybrids and both univalents and multivalents were observed. Multiplication of the interspecific hybrids was achieved through in vitro culture of nodal sections on Murashige & Skoog medium supplemented with 0.5 mg l^-1 benzyladenine. Fertility of the interspecific hybrids was improved by subjecting the in vitro proliferating shoots to 0.001% colchicine incorporated in the shoot multiplication medium. The amphiploids serve as fertile bridges and facilitate interspecific gene transfer through conventional breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gene transfer from non-tuberous to tuberous Solanum species: Evidence from meiosis in hybrids

Summary The distant hybrids between non-tuberous Solanum species and tuberous S. pinnatisectum display little or no pairing in F1 and predominantly bivalent formation (preferential pairing) after chromosome doubling. In such a situation the question about the potential and extent of gene transfer from the non-tuberous parent to the tuberous one is relevant to potato breeding. This question was investigated by studying meiosis in triploid and hexaploid hybrids from crosses between diploid TV⁵ x tetraploid (S. etuberosum x S. pinnatisectum). TV⁵ is similar to S. verrucosum with cytoplasm of S. tuberosum. The following evidence was found for the desirable transfer of S. etuberosum genes to the tuberous species.The triploid F1 hybrids did not display the configurations 12 II+12 I expected if no gene exchange would take place between S. etuberosum and the tuberous species; however, a considerable number of multivalents per cell was observed in all plants studied.In the hexaploid F1 hybrids, obtained from the triploids through somatic doubling in vitro, 36 bivalents could reasonably be expected. Although bivalents were predominant (an overall average of 24.2 per cell) quite a few chromosomes were associated as multivalents in all plants investigated.It is concluded that in the hybrids studied a considerable amount of pairing and chiasma formation occurs between chromosomes of non-tuberous and those of tuberous Solanum species. This pairing affinity is larger than that found in 2x and 4x hybrids from S. etuberosum x S. pinnatisectum. Some hypotheses are put forward to explain this increased pairing affinity.