New insights on the role of HCN in root hair elongation through single cell proteomics

Root hairs are specialized structures involved in water and nutrient uptake by plants. They elongate from epidermal cells following a complex developmental program. ß-cyanoalanine synthase (CAS), which is mainly involved in hydrogen cyanide (HCN) detoxification in Arabidopsis thaliana , plays a role in root hair elongation, as evidenced by the fact that cas-c1 mutants show a severe defect in root hair shape. In addition to root hairs, CAS C1 is expressed in the quiescent center and meristem. However, the cas-c1 mutation has no visible effect on either tissue, in both control and nutrient-deprivation conditions. To identify its role in root hair formation, we conducted single cell proteomics analysis by isolating root hair cells using Fluorescence-Activated Cell Sorting (FACS) from wild type and cas-c1 mutants. We also analyzed the presence of S -cyanylation, a protein post-translational modification (PTM) mediated by HCN and affecting cysteine residues and protein activity, in proteins of wild type and cas-c1 mutants. We found that several proteins involved in root hair development, related to the receptor kinase FERONIA signaling and to DNA methylation, are modified by this new post-translational modification. One sentence summary Arabidopsis root hair proteomics unveals that several proteins involved in root hair development are susceptible of modification by S -cyanylation.