BIG Modulates Stem Cell Niche and Meristem Development via SCR/SHR Pathway in Arabidopsis Roots.

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