Characterization of the GRAS transcription factor SCARECROW-LIKE 28's role in Arabidopsis root growth

The roles of multiple GRAS transcription factors (TFs), which play key roles in diverse processes of growth and development, have been characterized in detail. However, the regulatory functions of one third of the GRAS members remain unknown. Here, we characterized the role of SCARECROW-LIKE 28 (SCL28) in the Arabidopsis root; nuclear localization and transcriptional activity indicated that SCL28 likely acts as a TF in the root. SCL28 overexpression (SCL28-OX) promoted cell division and suppressed cell elongation in a zone-specific manner along the root axis. In the presence of the microtubule-destabilizing chemical propyzamide, SCL28-OX exhibited straight root growth, while scl28 roots showed left-handed helical growth similar to the wild type. Under salt and propyzamide treatments, scl28 roots grew straight, while SCL28-OX roots displayed exaggerated right-handed growth. Thus, SCL28 likely plays a role in the root growth response to stressinduced microtubule organization. Additionally, transcriptome analysis revealed that SCL28 regulated the transcription of diverse growth- and development-related genes in plants. In particular, SCL28 regulated the expression of various stressresponse genes. Taken together, our findings provide insight into the regulatory role of SCL28, which orchestrates the linked activity of cell division and elongation under various environmental conditions to achieve root growth plasticity.