The Glycine- and Proline-Rich Protein AtGPRP3 Negatively Regulates Plant Growth in Arabidopsis

Glycine- and proline-rich proteins (GPRPs) comprise a small conserved family that is widely distributed in the plant kingdom. GPRPs are relatively short peptides (<200 amino acids) that contain three typical domains, including an N-terminal XYPP-repeat domain, a middle hydrophobic domain rich in alanine, and a C-terminal HGK-repeat domain. These proteins have been proposed to play fundamental roles in plant growth and environmental adaptation, but their functions remain unknown. In this study, we selected an Arabidopsis GPRP (AtGPRP3) to profile the physiological role of GPRPs. Transcripts of AtGPRP3 could be detected in the whole Arabidopsis plant, but greater amounts were found in the rosette, followed by the cauline. The AtGPRP3::GFP fusion protein was mainly localized in the nucleus. The overexpression and knockout of AtGPRP3, respectively, retarded and accelerated the growth of Arabidopsis seedlings, while the increase in the growth rate of atgprp3 plants was offset by the complementary expression of AtGPRP3. CAT2 and CAT3, but not CAT1, interacted with AtGPRP3 in the nuclei of Arabidopsis protoplasts. The knockout of CAT2 by CRISPR-Cas9 retarded the growth of the Arabidopsis seedlings. Together, our data suggest that AtGPRP3 negatively regulates plant growth, potentially through CAT2 and CAT3.