Mikhailova E I, Naranjo T, Shepherd K, Wennekes-van Eden J, Heyting C, de Jong J H
Department of Genetics, Saint-Petersburg State University, Russia.
Chromosoma. 1998 Nov;107(5):339-50. doi: 10.1007/s004120050316.
The Ph1 locus in wheat influences homo(eo)logous chromosome pairing. We have analysed its effect on the behaviour and morphology of two 5RL rye telosomes in a wheat background, by genomic in situ hybridisation (GISH), using rye genomic DNA as a probe. Our main objective was to study the effect of different alleles of the Ph1 locus on the morphology and behaviour of the rye telosomes in interphase nuclei of tapetal cells and in pollen mother cells at early stages of meiosis. The telosomes, easily detectable at all stages, showed a brightly fluorescing chromomere in the distal region and a constriction in the proximal part. These diagnostic markers enabled us to define the centromere and telomere regions of the rye telosomes. In the presence of functional copies of Ph1, the rye telosomes associated at pre-leptotene, disjoined and reorganised their shape at leptotene, and became fully homologously paired at zygotene - pachytene. In plants without functional alleles (ph1bph1b), the rye telosomes displayed an aberrant morphology, their premeiotic associations were clearly disturbed and their pairing during zygotene and pachytene was reduced and irregular. The Ph1 locus also influenced the behaviour of rye telosomes in the interphase nuclei of tapetal cells: in Ph1Ph1 plants, the rye telosomes occupied distinct, parallel-oriented domains, whereas in tapetal nuclei of ph1bph1b plants they were intermingled with wheat chromosomes and showed a heavily distorted morphology. The results shed new light on the effect of Ph1, and suggest that this locus is involved in chromosome condensation and/or scaffold organisation. Our explanation might account for various apparently contradictory and pleiotropic effects of this locus on both premeiotic associations of homologues, the regulation of meiotic homo(eo)logous chromosome pairing and synapsis, the resolution of bivalent interlockings and centromere behaviour.
小麦中的Ph1位点影响同源染色体配对。我们通过基因组原位杂交（GISH），以黑麦基因组DNA为探针，分析了它对小麦背景下两个5RL黑麦端体行为和形态的影响。我们的主要目的是研究Ph1位点的不同等位基因对绒毡层细胞间期核和减数分裂早期花粉母细胞中黑麦端体形态和行为的影响。在所有阶段都易于检测到的端体，在远端区域显示出一个明亮荧光的染色粒，在近端部分有一个缢缩。这些诊断标记使我们能够确定黑麦端体的着丝粒和端粒区域。在存在功能性Ph1拷贝的情况下，黑麦端体在细线前期相互关联，在偶线期分离并重新组织其形状，并在偶线期 - 粗线期完全同源配对。在没有功能等位基因（ph1bph1b）的植物中，黑麦端体呈现异常形态，其减数分裂前的关联明显受到干扰，并且在偶线期和粗线期的配对减少且不规则。Ph1位点还影响了绒毡层细胞间期核中黑麦端体的行为：在Ph1Ph1植物中，黑麦端体占据不同的、平行排列的区域，而在ph1bph1b植物的绒毡层核中，它们与小麦染色体混合在一起，并呈现出严重扭曲的形态。这些结果为Ph1的作用提供了新的线索，并表明该位点参与染色体浓缩和/或支架组织。我们的解释可能说明了该位点对同源物减数分裂前关联、减数分裂同源染色体配对和联会的调节、二价体互锁的解决以及着丝粒行为的各种明显矛盾和多效性影响。
