Component of a nucleolar small nuclear ribonucleoprotein particle (snoRNP) thought to participate in the processing and modification of pre-ribosomal RNA (By similarity). Essential for embryogenesis. Plays a critical role in embryo sac development and gametic cell fate. Required for the correct positioning of the first division plane of zygote. May function during early embryogenesis (PubMed:20699009). Expressed in tissues with active in cell division such as shoot apexes, root tips, lateral root primordia, embryos, endosperm, pollen grains and embryo sacs. Strongly expressed in early embryos and endosperm, but very weakly in globular embryos and further embryo developmental stages. Embryonic lethality when homozygous. Belongs to the WD repeat RRP9 family.