CASPARIAN STRIP INTEGRITY FACTOR (CIF) family peptides - regulator of plant extracellular barriers

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2021-09, Vol.143, p.170599, Article 170599
• Main Author: Fujita, Satoshi
• Format: Article
• Language: English
• Subjects: Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Biological Transport; CASPARIAN STRIP INTEGRITY FACTORs (CIFs); Casparian strips; Cell Wall - metabolism; Embryonic cuticle; Extracellular barriers; Plant Proteins - metabolism; Receptor-peptide signaling pathway; Signal Transduction; TWISTED SEED1 (TWS1)
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/j.peptides.2021.170599

•Extracellular barriers substantially impact homeostasis by limiting the free diffusion of small molecules.•CIF family peptides are essential for functional extracellular barrier formation in plants.•Posttranslational sulfation and precise cleavage are critical for the activity of CIF family peptides.•CIF family peptides are SGN3/GSO1 and GSO2 ligands and activate genomic and non-genomic responses.•Barrier formation processes provide attractive models of spatial regulation in signaling pathways. In multicellular organisms, water and most of the small molecules, such as nutrients, toxic substances, and signaling compounds, move freely through extracellular spaces, depending on their biochemical nature. To restrict the simple diffusion of small molecules, multicellular organisms have evolved extracellular barriers across specific tissue layers, such as tight junctions in the animal epithelium. Similar extracellular barriers are also generated in plants through the accumulation of hydrophobic chemicals, such as lignin or cutin, although the detailed molecular mechanisms underlying this process remain elusive. Here, I summarize recent advances in extracellular barrier formation in plants by focusing mainly on CASPARIAN STRIP INTEGRITY FACTOR (CIF) family peptides, which trigger the spatially precise deposition of designated cell wall components, enabling plants to establish transcellular barrier networks correctly. The genome of Arabidopsis thaliana, a model plant species, harbors five CIF genes, which encode propeptides which are processed into small secreted peptides of 21–24 amino acids. Sulfation of tyrosine residues in CIF peptides ensures their full bioactivity and high-affinity binding to their receptors SCHENGEN3/GASSHO1 (SGN3/GSO1) and GSO2 in vitro. Additionally, in vivo analysis shows that physical restriction of CIF peptide diffusion and the subcellular localization of a signaling module and expression patterns of a peptide processing enzyme specify the location of signal activation. Thus, the CIF peptide family provides fascinating models for understanding mature peptide biogenesis and spatially limited signal activation with small diffusive molecules.