Arabidopsis lysin motif/F‐box‐containing protein InLYP1 fine‐tunes glycine metabolism by degrading glycine decarboxylase GLDP2

SUMMARY Lysin motif (LysM) is a carbohydrate‐binding module often found in secreted or transmembrane proteins in living organisms from prokaryotes to eukaryotes. Thus far, all characterized LysM‐containing proteins in plants are plasma membrane‐resident receptors or co‐receptors playing roles in plant–microbe interactions. Here, we interrogate the Arabidopsis LysM/F‐box‐containing protein InLYP1 and reveal its function in glycine metabolism. InLYP1 was mainly expressed by vigorously growing tissues, encoding a nuclear‐cytoplasmic protein. We validated InLYP1 as part of the SKP1‐CULLIN1‐F‐box E3 complex for mediating protein degradation. The glycine decarboxylase P‐protein 1 (GLDP1) was identified as an InLYP1‐interacting protein by both immunoprecipitation/mass spectrometry and yeast two‐hybrid library screening. InLYP1 could also interact with GLDP2, a paralog of GLDP1 with weaker catalytic activity, and could mediate the degradation of GLDP2 but not GLDP1. Interestingly, both GLDPs could be O ‐glycosylated and form homodimers or heterodimers. Overexpression of InLYP1 L9A encoding a dominant‐negative variant could cause seedling germination retardation on the medium containing glycine. Collectively, these results shed light on the function of plant intracellular LysM‐containing proteins, and suggest that InLYP1 may deplete GLDP2 to facilitate glycine decarboxylation in Arabidopsis.