CHROMOSOME-PAIRING AND CHIASMA FORMATION IN ALLOHEXAPLOID WHEAT, TRITICUM-AESTIVUM ANALYZED BY SPREADING OF MEIOTIC NUCLEI
CHROMOSOME-PAIRING AND CHIASMA FORMATION IN ALLOHEXAPLOID WHEAT, TRITICUM-AESTIVUM ANALYZED BY SPREADING OF MEIOTIC NUCLEI
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DOI：
10.1007/bf02906837
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发表时间：
1986-01-01
期刊：
影响因子：
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通讯作者：
HOLM, PB
中科院分区：
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作者：
HOLM, PB
对小麦（Triticum aestivum）扩散的银染色减数分裂核进行了超微结构分析。对许多瘦素和早期合成器细胞核的外侧成分和突触复合体的部分示图，以及11个中期合成器细胞核、7个晚期合成器细胞核、20个粗线细胞核、12个早期二倍体细胞核、21个中期二倍体细胞核和16个晚期二倍体细胞核的完整示图，得出了以下观察和结论：1)染色体在扩散的瘦素和早期合成器细胞核内似乎是随机分布的。2)补体长度（即三个基因组的横向成分长度）从平均2063 .mu减少。M在中期合成器到1806 .mu。M在晚合子蛋白和1474 .mu。我是pachytene。3)染色体配对优先从端粒开始。它们在受精卵形成期间聚集，从而形成染色体束。突触复合体的形成也在间隙中开始，在11个中间合子核中，平均每个细胞核有156个突触复合体片段，其中平均61%的补体是成对的。4)染色体配对和突触复合体的形成仍然经常不完整。然而，在大多数情况下，超过95%的补体发生了突触。侧边组分和突触复合体的联锁在接合蛋白处很常见。对一个中合子核的详细分析发现有20多个连锁，其中大多数是二价连锁。在合子期晚期，平均每个细胞核有5个二价连锁和少数染色体连锁。一些连锁一直持续到粗线期，少数可能持续到二倍体期。6)在11个中合子核中的8个、7个晚合子核中的4个、20个粗线核中的3个以及可能在一个早期二倍子核中可以看到染色体的多重结合，可能表示同源物之间的配对。7)突触复合体的降解始于粗线期向复合体过渡的有限位点，保留的突触复合体片段在早、中、后期分别为89个、119个和136个。这超过了光学显微镜在中期I观察到的交叉数的2到3倍。8)异源六倍体小麦的二倍体行为可能是由于：1)在受精卵开始时染色体配对的高度严格性，同源物之间优先启动配对。II)在杂交发生之前，在合子期末端和粗线期期间，多重结合转化为二价和/或III)同源染色体成对片段之间的杂交受到抑制。讨论了Ph基因对5B染色体长臂可能产生的影响。
An ultrastructural analysis of spread, silver stained meiotic nuclei of wheat, Triticum aestivum, has been performed. Partial tracings of lateral components and synaptonemal complexes of a number of leptotene and early zygotene nuclei, and complete tracings of eleven mid zygotene, seven late zygotene, twenty pachytene, twelve early diplotene, twenty-one mid diplotene and sixteen late diplotene nuclei have permitted the following observations and conclusions: 1) The chromosomes appear to be randomly distributed within the spread leptotene and early zygotene nuclei. 2) The complement length, i.e., the lateral component length of the three genomes, decrease from a mean of 2063 .mu.m at mid zygotene to 1806 .mu.m at late zygotene and 1474 .mu.m at pachytene. 3) Chromosome pairing is initiated preferentially from the teleomeres. These are aggregated during zygotene whereby a chromosome bouquet is established. Synaptonemal complex formation is thereafter also initiated interstitially, the mean number of synaptonemal complexe segments being 156 per nucleus in the eleven mid zygotene nuclei where on the average 61% of the complement is paired. 4) Chromosome pairing and synaptonemal complex formation remain frequently incomplete. In most cases, however, more than 95% of the complement has synapsed. 5) Interlocking of lateral components and synaptonemal complexes is frequent at zygotene. Detailed analysis of one mid zygotene nucleus revealed more than 20 interlockings, most of them being bivalent interlockings. At late zygotene there was a mean of 5 bivalent interlockings per nucleus and a few chromosome interlockings. Some interlockings persist up to pachytene and a few may remain into diplotene. 6) Multiple associations of chromosomes, probably signifying pairings between homoeologues, are seen in eight of the eleven mid zygotene nuclei, in four of the seven late zygotene nuclei, in three of the 20 pachytene nuclei and possibly in one of the early diplotene nuclei. 7) Synaptonemal complex degradation is initiated at a limited number of sites at the pachytene to diplotene transition, the number of retained synaptonemal complex segments amount to 89, 119 ans 136 at early, mid and late diplotene. This exceeds the number of chiasmata observable at metaphase I in the light microscope by a factor of two to three. 8) It is proposed that the diploid behavior of allohexaploid wheat result from: I) A high stringency of chromosome pairing at the beginning of zygotene whereby pairing preferentially is initiated between homologues. II) Transformation of multiple association into bivalent at the end of zygotene and during pachytene before crossing over occurs and/or III) a suppression of crossing over between paired segments of homoeologous chromosomes. The possible effect of the Ph gene(s) on the long arm of chromosome 5B is discussed.