The Proliferating cell nuclear antigen (PCNA) complex is a crucial component of the replication fork protein complex (replisome). PCNA, acting as a DNA sliding clamp during replication, playing key roles in DNA replication, repair and cell cycle regulation. While extensively studied in yeast and metazoans, the functional specialization of PCNA homologs in plants remains largely unexplored. The model plant Arabidopsis thaliana contains two PCNA homologs, PCNA1 and PCNA2, which share high sequence similarity but exhibit different functions under DNA damage stress. Key amino acid residues K/N201 and N/K262 are associated with the functional differences of these homologues, which may undergo to post-translational modifications influencing PCNA stability and repair pathway choice. Our study aims to investigate differences between Arabidopsis PCNA1 and PCNA2. We will analyze their viability, growth phenotypes, and responses to replication stress. Additionally, in vivo imaging will reveal the nuclear localization and recruitment dynamics of PCNA1 and PCNA2 at DNA damage sites. We will also investigate the interplay between PCNA and the 9-1-1 checkpoint complex, which functions in DNA damage response, and the role of Replication factor C (RFC) complexes in PCNA (un)loading. A key focus will be the newly discovered ELG1 homolog, a putative PCNA unloader.