May modulate the level of one or more small signaling molecules that have a role in regulating meristem function. May play a role in balancing and restricting the meristem-promoting activity of auxin signaling (PubMed:17553903). Involved in ethylene and giberellin (GA) signaling pathways or in a parallel pathway controlling cell and hypocotyl elongation and cellular organization (PubMed:17006669). Involved in abscisic acid (ABA) signaling pathway. Plays a negative role in ABA-mediated seed germination and seedling development (PubMed:23603279). Acts in association with LAMP1 to suppress ectopic stem cell niche formation in the shoot apical meristem (SAM) independently of cytokinin signaling pathway (PubMed:25673776). Modulates responses to ABA, oxidative stress and abotic stress (PubMed:23621575). Acts as negative regulator of the ABA signaling pathway to modulate freezing and drought stress responses. Mediates carbon and amino acid metabolism (PubMed:23621575, PubMed:23603279). May be involved in the acquisition and/or maintenance of seed dormancy (PubMed:21637772). Involved in the regulation of response to heat shock and plant defense (PubMed:27743891). Release of an unsubstituted, C-terminal glutamyl residue, typically from Ac-Asp-Glu or folylpoly-gamma-glutamates. Binds 2 Zn(2+) ions per subunit. Expressed in all plant parts. Highest levels in the bolt stem, inflorescence, root and silique. Low level in leaves. Down-regulated by abscisic acid (ABA). Belongs to the peptidase M28 family. M28B subfamily.