Chromosome pairing in allohexaploid wheat var. Chinese Spring. Transformation of multivalents into bivalents, a mechanism for exclusive bivalent formation

摘要: Meiosis in allohexaploid wheat, Triticum aestivum var. Chinese Spring has been investigated by complete three dimensional reconstructions of a late zygotene and an early pachytene nucleus. At zygotene, specific synapsis homologous chromosomes chromosome segments gives rise to extensive multivalent formation with shifts pairing partners between apparently homoeologous chromosomes. These observations were confirmed the identification serial sectioned, but only partly reconstructed nuclei. In striking contrast, at was exclusively bivalents. findings, which are consistent pattern described tri- tetraploid Bombyx oocytes, definitely exclude presynaptic alignment as primary cause for regular bivalent formation, wheat. Instead, multivalents form during later transformed into bivalents through dissolution reassembly synaptonemal, complexes. It is proposed that wheat due temporal delay crossing over until correction completed pachytene. This may be mediated action Ph gene(s) on 5B. Finally, interlockings revealed completely nucleus resolved prior