CTF7 is an essential gene in yeast that is required for the formation of sister chromatid cohesion. While recent studies have provided insights into how sister chromatid cohesion is established, less is known about how specifically CTF7 facilitates the formation of cohesion, and essentially nothing is known about how sister chromatid cohesion is established in plants. In this report, we describe the isolation and characterization of CTF7 from Arabidopsis (Arabidopsis thaliana). Arabidopsis CTF7 is similar to Saccharomyces cerevisiae CTF7 in that it lacks an amino-terminal extension, exhibits acetyltransferase activity, and can complement a yeast ctf7 temperature-sensitive mutation. CTF7 transcripts are found throughout the plant, with the highest levels present in buds. Seeds containing T-DNA insertions in CTF7 exhibit mitotic defects in the zygote. Interestingly, the endosperm developed normally in ctf7 seeds, suggesting that CTF7 is not essential for mitosis in endosperm nuclei. Minor defects were observed in female gametophytes of ctf7 1/2 plants, and plants that overexpress CTF7 exhibited female gametophyte lethality. Pollen development appeared normal in both CTF7 knockout and overexpression plants. Therefore, proper levels of CTF7 are critical for female gametophyte and embryo development but not for the establishment of mitotic cohesion during microgametogenesis or during endosperm development.The proper formation of sister chromatid cohesion and its subsequent release at the metaphase-to-anaphase transition is essential for the proper segregation of genetic material during cell division. It is critical for the compaction of chromosomes and their bipolar attachment to the spindle, DNA double-strand break repair, and the regulation of gene expression (for review, see Nasmyth and Haering, 2009). Sister chromatid cohesion is controlled by the cohesin complex, which consists of a heterodimer of Structural Maintenance of Chromosome (SMC) proteins, SMC1 and SMC3, Sister Chromatid Cohesion (SCC) protein SCC3, and SCC1, an a-kleisin protein. Perhaps the most widely accepted model of how cohesin functions has been referred to as the ring model, where the cohesin ring encircles the replicated sisters, holding them together until SCC1 cleavage by separase at the metaphase-to-anaphase transition opens the ring, allowing the release of the sister chromatids (for review, see Nasmyth and Haering, 2009).