Král Jirí
Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Vinicná 5, CZ-128 44, Prague 2, Czech Republic.
Chromosome Res. 2007;15(7):863-79. doi: 10.1007/s10577-007-1169-3. Epub 2007 Oct 1.
Most spiders exhibit a multiple sex chromosome system, X(1)X(2)0, whose origin has not been satisfactorily explained. Examination of the sex chromosome systems in the spider genus Malthonica (Agelenidae) revealed considerable diversity in sex chromosome constitution within this group. Besides modes X(1)X(2)0 (M. silvestris) and X(1)X(2)X(3)0 (M. campestris), a neo-X(1)X(2)X(3)X(4)X(5)Y system in M. ferruginea was found. Ultrastructural analysis of spread pachytene spermatocytes revealed that the X(1)X(2)0 and X(1)X(2)X(3)0 systems include a pair of homomorphic sex chromosomes. Multiple X chromosomes and the pair exhibit an end-to-end pairing, being connected by attachment plaques. The X(1)X(2)X(3)X(4)X(5)Y system of M. ferruginea arose by rearrangement between the homomorphic sex chromosome pair and an autosome. Multiple X chromosomes and the sex chromosome pair do not differ from autosomes in a pattern of constitutive heterochromatin. Ultrastructural data on sex chromosome pairing in other spiders indicate that the homomorphic sex chromosome pair forms an integral part of the spider sex chromosome systems. It is suggested that this pair represents ancestral sex chromosomes of spiders, which generated multiple X chromosomes by non-disjunctions. Structural differentiation of newly formed X chromosomes has been facilitated by heterochromatinization of sex chromosome bivalents observed in prophase I of spider females.
大多数蜘蛛表现出一种多性染色体系统，即X(1)X(2)0，其起源尚未得到令人满意的解释。对蜘蛛类属Malthonica（漏斗蛛科）的性染色体系统进行研究发现，该类群中性染色体组成存在相当大的多样性。除了X(1)X(2)0模式（M. silvestris）和X(1)X(2)X(3)0模式（M. campestris）外，还在M. ferruginea中发现了一种新的X(1)X(2)X(3)X(4)X(5)Y系统。对伸展的粗线期精母细胞的超微结构分析表明，X(1)X(2)0和X(1)X(2)X(3)0系统包括一对同形性染色体。多条X染色体和这对染色体呈现端对端配对，通过附着斑相连。M. ferruginea的X(1)X(2)X(3)X(4)X(5)Y系统是由同形性染色体对与一条常染色体之间的重排产生的。多条X染色体和性染色体对在组成型异染色质模式上与常染色体并无差异。其他蜘蛛中性染色体配对的超微结构数据表明，同形性染色体对是蜘蛛性染色体系统的一个组成部分。有人认为，这对染色体代表蜘蛛的祖先性染色体，它们通过不分离产生了多条X染色体。蜘蛛雌性减数分裂前期I中观察到的性染色体二价体的异染色质化促进了新形成的X染色体的结构分化。
