Dvorak J, Lukaszewski A J
Department of Agronomy and Range Science, University of California, Davis 95616, USA.
Chromosoma. 2000 Sep;109(6):410-4. doi: 10.1007/s004120000093.
Chiasmate pairing between homoeologous chromosomes at metaphase I (MI) of meiosis in wheat is prevented by the activity of the Ph1 locus on chromosome 5B. Several hypotheses have been proposed sharing the assumption that Ph1 regulates MI chromosome pairing by regulating centromere-mediated chromosome alignment before the onset of meiosis. To test the relevance of the putative predetermination of chromosome pairing at MI by the centromere-mediated chromosome association prior to meiosis, a 2BL.2RL homoeoisochromosome was constructed and its MI pairing was assessed in the presence and absence of the Ph1 locus. Although the 2BL and 2RL arms of the homoeoisochromosome paired with each other at MI in the absence of Ph1, they never paired with each other at MI in the presence of Ph1. Since the two arms were permanently associated in the homoeoisochromosome via a common centromere, it is unlikely that Ph1 predetermines MI pairing between homoeologous chromosomes solely by controlling premeiotic association of centromeres. These findings are consistent with the idea that Ph1 determines the chromosome pairing pattern at MI by scrutinizing homology across the entire chromosome.
小麦减数分裂中期I（MI）同源染色体之间的交叉配对受到5B染色体上Ph1位点活性的抑制。已经提出了几种假说，这些假说都假定Ph1通过在减数分裂开始前调节着丝粒介导的染色体排列来调控MI期染色体配对。为了检验减数分裂前着丝粒介导的染色体联会对MI期染色体配对的假定预先决定作用的相关性，构建了一条2BL.2RL同臂异染色体，并在有和没有Ph1位点的情况下评估其MI期配对情况。尽管在没有Ph1的情况下，同臂异染色体的2BL和2RL臂在MI期相互配对，但在有Ph1的情况下，它们在MI期从未相互配对。由于两条臂通过共同的着丝粒在同臂异染色体中永久联会，因此Ph1不太可能仅通过控制减数分裂前着丝粒的联会来预先决定同源染色体之间的MI期配对。这些发现与以下观点一致，即Ph1通过审查整个染色体上的同源性来决定MI期的染色体配对模式。
