As accessory component of DNA polymerase II participates in chromosomal DNA replication. Required for the timing and determination of cell fate during plant embryogenesis and root pole development, by promoting cell cycle and cell type patterning. Necessary for proper shoot (SAM) and root apical meristem (RAM) functions (By similarity). Is essential to promote the first divisions of the zygote (PubMed:16212602). Subunit of the DNA polymerase II (Probable). Interacts with POL2A (via C-terminus) (PubMed:16212602). During plant development, expressed in the shoot and root meristematic regions, but not inthe meristems in seeds at germination nor in trichomes undergoing endoreduplication. During male gametogenesis, transiently expressed in immature pollen grains at the time of post-meiotic mitosis, but not in the female macrospores at any time of development. Expressed in the embryo sac after fertilization and the in the embryo proper and suspensor cells until the globular stage. At the triangular stage, expressed in the forming shoot apical meristem. Cell cycle regulated. Up-regulated at the G1/S phase transition and then decreases rapidly as cells progress into S-phase. Embryonic lethality when homozygous, due to embryo development arrested at one-cell stage. Belongs to the DNA polymerase epsilon subunit B family.