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BIG, a regulator of polar auxin transport, is necessary to regulate the growth and development of Arabidopsis. Although mutations in the <i>BIG</i> gene cause severe root developmental defects, the exact mechanism remains unclear. Here, we report that disruption of the <i>BIG</i> gene resulted in decreased quiescent center (QC) activity and columella cell numbers, which was accompanied by the downregulation of <i>WUSCHEL-RELATED HOMEOBOX5</i> (<i>WOX5</i>) gene expression. BIG affected auxin distribution by regulating the expression of PIN-FORMED proteins (PINs), but the root morphological defects of <i>big</i> mutants could not be rescued solely by increasing auxin transport. Although the loss of <i>BIG</i> gene function resulted in decreased expression of the <i>PLT1</i> and <i>PLT2</i> genes, genetic interaction assays indicate that this is not the main reason for the root morphological defects of <i>big</i> mutants. Furthermore, genetic interaction assays suggest that BIG affects the stem cell niche (SCN) activity through the SCRSCARECROW (SCR)/SHORT ROOT (SHR) pathway and BIG disruption reduces the expression of <i>SCR</i> and <i>SHR</i> genes. In conclusion, our findings reveal that the <i>BIG</i> gene maintains root meristem activity and SCN integrity mainly through the SCR/SHR pathway.