The Cell Cycle Timing of Centromeric Chromatin Assembly in Drosophila Meiosis Is Distinct from Mitosis Yet Requires CAL1 and CENP-C
CID assembly occurs in prophase of meiosis I, resulting in a greater than 2-fold increase in CID at centromeres from S1 to M1 stages. CID drops by half (CID level = 2, relative to starting levels in S1) due to chromosome segregation in meiosis I; additional loss of CID is observed between telophase I and the beginning of meiosis II (CID level = 1.5). CID drops by half due to chromosome segregation in meiosis II with no assembly (CID level = 0.75). A second phase of CID assembly occurs beginning in T1 spermatids and continuing in T2–T5 spermatids in larvae (CID level = 1.25). In larvae, the level of centromeric CID in T5 haploid spermatids is comparable to the level at the S1 stage before the meiotic divisions. In adults, the level of centromeric CID in late canoe stage spermatids is also comparable to the level at the S1 stage.