Exogenous application of plant hormone abscisic acid (ABA) can inhibit root growth. We recently reported that the proline-rich extensin-like receptor kinase 4 (PERK4) functions at an early stage of ABA signaling to inhibit primary root cell elongation by perturbing Ca2+ homeostasis.(1) Transcription analysis indicated that PERK4 modulates the expression of the genes related to cell elongation and ABA signaling in root growth, such as polygalacturonases, AtExt1, AtMYC2 and ABR1. Under ABA treatment, the transcript level of ZAT10, a Ca(2+)-responsive gene, increased in perk4 plants compared to that of wild-type. Based on both present data and the previous evidence, we propose a probable model for PERK4-mediated ABA-regulated primary root cell growth.