Fig. 3.

The adult germline and embryo show distinct patterns of PCN-1 nuclear accumulation. The inner circle represents the stages of the cell cycle; DNA replication occurs in S-phase (green), mitosis occurs in M phase (pink), and these are separated by G2 and a very short G1 phase (blue) [1]. Germline stem cells progress to meiotic S-phase and meiosis (gray). The outer circle represents nuclear accumulation of PCN-1 (red). Germline stem cells in C. elegans display a more typical mitotic cell cycle with gap phases and also display constant (non-cycling) accumulation of several proteins, including PCN-1 and CYE-1, which have been reported to display cell cycle regulated accumulation in other tissues and organisms (a) [1, 22]. By contrast, early embryos in C. elegans display a simplified cell cycle (S,M), and PCN-1, like several other cell cycle proteins, show nuclear accumulation only during S-phase (b) [9, 10]