EFFECT OF THE PAIRING GENE PH1 ON CENTROMERE MISDIVISION IN COMMON WHEAT

The cytologically diploid-like meiotic behavior of hexaploid wheat (i. e., exclusive bivalent pairing of homologues) is largely controlled by the pairing homoeologous gene Ph1. This gene suppresses pairing betwe en homoeologous (partially homologous) chromosomes of the three closel y related genomes that compose the hexaploid wheat complement. It has been previously proposed that Ph1 regulates meiotic pairing by determi ning the pattern of premeiotic arrangement of homologous and homoeolog ous chromosomes. We therefore assume that Phl action may be targeted a t the interaction of centromeres with spindle microtubules-an interact ion that is critical for movement of chromosomes to their specific int erphase positions. Using monosomic lines of common wheat, we studied t he effect of this gene on types and rates of centromere division of un ivalents at meiosis. In the presence of the normal two doses of Phl, t he frequency of transverse breakage (misdivision) of the centromere of univalent chromosomes was high in both first and second meiotic divis ions; whereas with zero dose of the gene, this frequency was drastical ly reduced. The results suggest that Ph1 is a trans-acting gene affect ing centromere-microtubules interaction. The findings are discussed in the context of the effect of Ph1 on interphase chromosome arrangement .