Abstract
BRAHMA (BRM), a SWI/SNF chromatin remodeling ATPase, is essential for the transcriptional reprogramming associated with development and cell differentiation in Arabidopsis thaliana. In this study, we show that loss-of-function mutations in BRM led to defective maintenance of the root stem cell niche, decreased meristematic activity, and stunted root growth. Mutations of BRM affected auxin distribution by reducing local expression of several PIN-FORMED (PIN) genes in the stem cells and impaired the expression of the stem cell transcription factor genes PLETHORA (PLT1) and PLT2. Chromatin immunoprecipitation assays showed that BRM could directly target to the chromatin of PIN1, PIN2, PIN3, PIN4, and PIN7. In addition, genetic interaction assays indicate that PLTs acted downstream of BRM, and overexpression of PLT2 partially rescued the stem cell niche defect of brm mutants. Taken together, these results support the idea that BRM acts in the PLT pathway to maintain the root stem cell niche by altering the expression of PINs.