Auxiliary subunit of the NatB N-alpha-acetyltransferase complex. Required for flowering time regulation and for vegetative and reproductive plant development. Ubiquitously expressed, with a higher expression in vascular bundles, hydathodes, leaf primordia and the base of the trichomes. Leaf reticulation, mild leaf folding, early flowering and aborted or unfertilized ovules in siliques (PubMed:24244708). No stunted growth or enhanced resistance to pathogens (PubMed:25966763). Belongs to the MDM20/NAA25 family.