The Signal from the Initiation of Meiotic Recombination to the First Division of Meiosis

Abstract

Two of the unique events that occur in meiosis are high levels of genetic recombination and the reductional division. Our previous work demonstrated that the REC102 , REC104 , REC114 , and RAD50 genes, required to initiate meiotic recombination in Saccharomyces cerevisiae , are needed for the proper timing of the first meiotic (MI) division. If these genes are absent, the MI division actually begins at an earlier time. This paper demonstrates that the meiotic recombination genes MER2/REC107 , SPO11 , and MRE2 and the synaptonemal complex genes HOP1 and RED1 are also required for the normal delay of the MI division. A rec103/ski8 mutant starts the MI division at the same time as in wild-type cells. Our data indicate no obvious correlation between the timing of premeiotic S phase and the timing of the first division in Rec ⁻ mutants. Cells with rec102 or rec104 mutations form MI spindles before wild-type cells, suggesting that the initiation signal acts prior to spindle formation. Neither RAD9 nor RAD24 is needed to transduce the signal, which delays the first division. The timing of the MI division in RAD24 mutants indicates that the pachytene checkpoint is not active in Rec ⁺ cells and suggests that the coordination between recombination and the MI division in wild-type cells may occur primarily due to the initiation signal. Finally, at least one of the targets of the recombination initiation signal is the NDT80 gene, a transcriptional regulator of middle meiotic gene expression required for the first division.