Lukaszewski Adam J
Department of Botany and Plant Science, University of California Riverside, Riverside, California, USA.
Cytogenet Genome Res. 2024;164(3-4):165-169. doi: 10.1159/000541484. Epub 2024 Sep 19.
The Ph1 locus in polyploid wheat enforces strictly bivalent behaviour in meiotic metaphase I, by preventing homoeologues from crossing over. It has always been considered as completely dominant as no homoeologous metaphase I pairing has ever been detected with its single dose present. However, Ph1 also affects pairing and crossing over of homologous chromosomes.
Homologous crossover frequencies with Ph1 in two, one, and null doses were scored cytologically, as exchanges within a ca. 9.5-9.9 Mbp terminal wheat segment of a wheat-rye translocation T-9 and corresponding segments in chromosome arms 1BS originating from four wheat cultivars.
In all cases, the crossover rates in the tested homologous segment of wheat genome, with a single dose of Ph1 present, were intermediate between those at two and null Ph1 doses. Averaging across all four chromosomes, the crossover rate with a single dose of Ph1 present was 37% higher from that with two doses and 46.4% lower of that with a zero dosage.
The Ph1 locus in wheat affects homologues and appears to operate in a dosage-dependent manner.
多倍体小麦中的Ph1位点通过阻止部分同源染色体交叉，在减数分裂中期I严格控制二价体行为。由于从未检测到单剂量Ph1存在时的部分同源中期I配对情况，它一直被认为是完全显性的。然而，Ph1也会影响同源染色体的配对和交叉。
通过细胞学方法对具有两个、一个和零剂量Ph1时的同源交叉频率进行评分，将其作为小麦-黑麦易位系T-9约9.5 - 9.9 Mbp末端小麦片段内以及源自四个小麦品种的1BS染色体臂上相应片段内的交换情况。
在所有情况下，小麦基因组测试同源片段中存在单剂量Ph1时的交叉率介于两个剂量和零剂量Ph1时的交叉率之间。对所有四条染色体进行平均，存在单剂量Ph1时的交叉率比两个剂量时高37%，比零剂量时低46.4%。
小麦中的Ph1位点影响同源染色体，且似乎以剂量依赖的方式起作用。
