CHROMOSOME-PAIRING, RECOMBINATION NODULES AND CHIASMA FORMATION IN THE BASIDIOMYCETE COPRINUS CINEREUS
CHROMOSOME-PAIRING, RECOMBINATION NODULES AND CHIASMA FORMATION IN THE BASIDIOMYCETE COPRINUS CINEREUS
复制标题
DOI：
10.1007/bf02906519
复制
发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
SAGE, J
中科院分区：
文献类型：
--
作者：
HOLM, PB;RASMUSSEN, SW;SAGE, J
根据联会复合体、着丝粒和中心体的形态，对94个完全重建的细胞核进行了时间序列分析，得到了以下观察结果和结论。C. cinereus是13。已在菌株PR 2301和E991中鉴定出相互易位。在前一种菌株中，易位发生在3号和5号染色体之间，而在后一种菌株中，易位发生在1号和9号染色体之间。染色体互锁和染色体断裂存在于偶线期，但频率低于染色体较长的生物体。易位四价体比正常二价体更常参与互锁，并有更多的染色体断裂。一个易位四价转化成2个异形二价体，只观察到一次，这与论点一致，即这种转化所需的联会复合体的营业额被阻止在二价区，其中发生了交叉。断裂-重聚机制对连锁的纠正在粗线期中晚期之前完成。在至少一个（可能是几个）病例中，2个明显正常的二价体取代了易位四价体，这表明发生了易位，可能是通过类似于负责联锁解决的机制。这种可能性的影响进行了讨论。在双线期早期，联会复合体从二价臂中消失，而联会复合体成分通常保持与着丝粒和交叉相关联，直到双线期晚期。同形核着丝粒区域至少在终变期早期保持融合。这种结合可能与交叉在维持二价体构型直到中期I方面起着相同的作用，因此提高了没有交叉的二价体中规则分离的机会。从偶线期早期到双线期晚期，联会复合体的中央区域容易识别出分裂结节。在偶线期晚期完成联会复合体形成后，预计结节总数为37个，与粗线期早期观察到的相同。在粗线期中晚期之前，结节的总数减少到26个，这与其他生物体中报告的减少相似。在粗线期、双线期和双线期晚期，越来越多的结节变大并被染色质包围，所有的结节都被小的染色质浓缩、交叉所取代。通过比较观察到的分布和由计算机模拟随机定位的结节产生的分布，分析了结节在二价体之间和沿着二价体的分布。分析表明，在偶线期晚期几乎是随机分布的，而在粗线期早期，特别是在中-晚粗线期，结节的分布偏离了随机分布。比较还表明，重组结节的二价核上的位置是由结节/二价（二价臂）的相互作用，而结节之间的相互作用似乎是不太重要。
The analysis of 94 completely reconstructed nuclei arranged in a temporal sequence according to the morphology of the synaptonemal complex, the centromeres and the centrosomes permitted the following observations and conclusions. The haploid chromosome number of C. cinereus is 13. Reciprocal translocations have been identified in strains PR2301 and E991. In the former strain, the translocation is between chromosomes 3 and 5 and in the latter between chromosomes 1 and 9. Interlockings and chromosome breaks are present during zygotene but at a lower frequency than in organisms with longer chromosomes. The translocation quadrivalents are more often than normal bivalents involved in interlockings and have more chromosome breaks. Transformation of a translocation quadrivalent into 2 heteromorphic bivalents was only observed once in agreement with the contention that the turnover of the synaptonemal complex required for this transformation is prevented in bivalent regions where crossing over has occurred. Correction of interlockings by the breakage-reunion mechanism is complete before mid-late pachytene. The presence of 2 apparently normal bivalents replacing the translocation quadrivalent in at least one, possibly several, cases suggests that a retranslocation has taken place, possibly by a mechanism similar to that responsible for the resolution of interlockings. The implications of this possibility are discussed. During early diplotene the synaptonemal complexes are eliminated from the bivalent arms while synaptonemal complex constituents often remain associated with the centromeres and the chiasmata until late diplotene. Homologous centromere regions remain fused at least until early diakinesis. This association may serve the same function as chiasmata in maintaining the bivalent configuration up to metaphase I and hence improve the chances of a regular disjunction in bivalents without chiasmata. Recombination nodules are readily identified in the central region of the synaptonemal complex from early zygotene to late diplotene. The total number of nodules expected upon completion of synaptonemal complex formation at late zygotene amounts to 37 and is the same as that observed at early pachytene. The total number of nodules is reduced to 26 before mid-late pachytene, a reduction similar to that reported in other organisms. An increasing fraction of the nodules becomes larger and surrounded by chromatin during pachytene, diplotene and by late diplotene, all nodules are replaced by small chromatin condensations, chiasmata. The distribution of nodules among and along the bivalents has been analyzed by comparing the observed distributions and those produced by computer simulation of a random positioning of nodules. The analysis reveals a nearly random distribution at late zygotene while during early pachytene and especially pronounced at mid-late pachytene, the distribution of nodules deviates from a random distribution. The comparison furthermore indicates that the placement of recombination nodules on the bivalents of a nucleus is controlled by nodule/bivalent (bivalent arm) interactions while the interaction between nodules appears to be of less importance.