The appearance of DNA breakage and repair activities in the synchronous meiotic cycle of Lilium

Abstract

The appearance of three complementary DNA breakage and repair activities is observed during the zygotene-pachytene stages of meiotic prophase in lily microsporocytes. The appearance of these DNA metabolic activities is correlated in time when homologous chromosomes pair and when a DNA repair replication synthesis is observed. One enzymic activity which appears is an endonuclease that produces repairable single-strand DNA breaks with 5′-hydroxyl termini. The endonuclease is accompanied in its appearance by two DNA repair activities, polynucleotidase kinase and polynucleotide ligase. Polynucleotide kinase can phosphorylate 5′-hydroxyl termini produced by the endonuclease and polynucleotide ligase can join the resulting 5′-phosphate to a juxtapositioned 3′- terminus. It is proposed that these activities compose a breakage and reunion mechanism responsible for genetic recombination activities in meiosis.