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

中文翻译：

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BIG 通过拟南芥根中的 SCR/SHR 通路调节干细胞生态位和分生组织发育

BIG 是极性生长素转运的调节剂，是调节拟南芥生长发育所必需的。尽管BIG基因的突变导致严重的根发育缺陷，但确切的机制仍不清楚。在这里，我们报告BIG基因的破坏导致静止中心 (QC) 活性和小柱细胞数量减少，这伴随着WUSCHEL 相关 HOMEOBOX5 ( WOX5 ) 基因表达的下调。BIG 通过调节 PIN-FORMED 蛋白 (PINs) 的表达来影响生长素的分布，但大突变体的根部形态缺陷不能仅通过增加生长素转运来挽救。虽然损失了BIG基因功能导致PLT1和PLT2基因表达降低，遗传相互作用分析表明这不是大突变体根部形态缺陷的主要原因。此外，遗传相互作用分析表明，BIG 通过 SCRSCARECROW (SCR)/SHORT ROOT (SHR) 途径影响干细胞生态位 (SCN) 活性，BIG 破坏降低了SCR和SHR基因的表达。总之，我们的研究结果表明，BIG基因主要通过 SCR/SHR 途径维持根分生组织活性和 SCN 完整性。