Regulatory subunit of glucosidase II (By similarity). Essential for stable accumulation of the receptor EFR that determines the specific perception of bacterial elongation factor Tu (EF-Tu), a potent elicitor of the defense response to pathogen-associated molecular patterns (PAMPs). Required for sustained activation of EFR-mediated signaling, but not receptor FLS2-mediated signaling elicited by the bacterial flagellin flg22. Glycan metabolism; N-glycan metabolism. Heterodimer of a catalytic alpha subunit (PSL5) and a beta subunit (PSL4). Expressed in roots, rosette leaves, leaf blades, mature stems, cauline leaves, flower buds, flowers and siliques. No visible phenotype under normal growth conditions, but mutant plants have compromised defense response induced by the bacterial elicitor elongation factor Tu (EF-Tu).