Benavente E, Santos J L
Departamento de Genética, E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Spain.
Cytogenet Cell Genet. 1993;62(1):5-10. doi: 10.1159/000133433.
Meiotic behavior has been investigated in rye plants carrying a heterozygous ditelocentric substitution for chromosomes 1R and 3R. Such a chromosomal rearrangement replaces a biarmed chromosome with two telocentrics, a situation karyotypically comparable to a Robertsonian translocation. As in Robertsonian translocation heterozygotes, delayed pairing characterizes the centromeric region in the rye pachytene heteromorphic trivalents. In addition, telocentric axes appear to be frequently engaged in nonhomologous synapsis (e.g., fold-back loops and two-by-two heterosynapsis) at their centromeric ends. Unlike those in Robertsonian translocation heterozygotes, the synaptic abnormalities detected here cannot be due to lack of partner homology. Rather, the chromosomal rearrangement itself appears to interfere with normal synaptonemal complex (SC) progression. The synaptic irregularities, which often result in complex pachytene multivalents, seem to have no effect on chiasma formation, since the rearranged pairs behave properly at metaphase I. Finally, differences in both SC length and progression patterns between plants and animals could explain the trans configurations of telocentric centromeres in plants, whereas only cis configurations of acrocentric kinetochores have been described in animals.
对携带1R和3R染色体杂合双着丝粒替代的黑麦植株的减数分裂行为进行了研究。这种染色体重排用两个端着丝粒取代了一个双臂染色体，这种情况在核型上类似于罗伯逊易位。与罗伯逊易位杂合子一样，黑麦粗线期异形三价体的着丝粒区域配对延迟。此外，端着丝粒轴在其着丝粒末端似乎经常参与非同源联会（例如，折返环和两两异源联会）。与罗伯逊易位杂合子不同，这里检测到的联会异常并非由于缺乏同源配对。相反，染色体重排本身似乎会干扰正常的联会复合体（SC）进程。这些经常导致复杂粗线期多价体的联会不规则现象，似乎对交叉形成没有影响，因为重排的配对在中期I表现正常。最后，动植物之间SC长度和进程模式的差异可以解释植物中端着丝粒着丝粒的反式构型，而在动物中仅描述了近端着丝粒动粒的顺式构型。
