Required for maturation of ribosomal RNAs and formation of the large ribosomal subunit (By similarity). Plays an essential role in cell growth and survival through its regulation of ribosome biogenesis and mitotic progression (PubMed:23909681). Required for normal root cell growth and differentiation (PubMed:25443833). Interacts with BOP1 and WDR12 (PubMed:23909681, PubMed:25443833). Interacts with NSN1 (PubMed:26163696). Localizes in the granular component (GC) region of the nucleolus. Expressed in shoot and root apical meristems, epidermal cells and vasculature of developing leaves, trichome progenitor cells, young flowers, developing pollen grains and ovules, and mature pollen grains. Plants silencing PES display severely compromised root meristem structures and a reduction of the primary root length of up to two-thirds. Belongs to the pescadillo family.