The auxin-regulated CrRLK1L kinase ERULUS controls cell wall composition during root hair tip growth ($) (Curr Biol)

Root hair outgrowth requires the plant hormone auxin and polarized tip growth and cell wall deposition. Schoenaers et al. showed that the plasma membrane-localized receptor-like kinase ERULUS (ERU) regulates tip growth in root hairs. ERU is regulated by auxin via ARF7 and ARF19 transcription factors, which directly bind to the promoter of ERU. The function of ERU is phosphorylation dependent, and exogenous NAA induces the phosphorylation of ERU at the cytoplasmic domain. ERU alters cell wall composition and pectin metabolism via PME (Pectin Methyltransferase) regulation. Phosphoproteomic results indicated that in the eru mutant phosphopeptide abundance of FER (FERONIA) was increased and that of AHA1/2 (H⁺-ATPase 1/2) was decreased. Taken together, this work shows the function of ERULUS in auxin-regulated alteration of cell wall composition for root hair tip growth. (Summary by Arif Ashraf) Current Biology: 10.1016/j.cub.2018.01.050