Primary root is the basic component of root system and plays a key role in early seedling growth and survival in rice. However, the molecular mechanism of primary root elongation still needs to be well understood. Here, we showed that OsWOX4, a WUSCHEL-related homeobox (WOX) transcription factor, was involved in the primary root elongation in rice. Silencing of OsWOX4 by RNA interference (RNAi) greatly increased the primary root length, whereas its overexpression reduced primary root elongation significantly. Moreover, the size of meristem zone and epidermal cell length of mature zone in RNAi root tips were drastically enhanced, while they were reduced markedly in overexpression lines, in comparison with that of wild type. Further analysis showed that the accumulation of free IAA was slightly increased in RNAi roots, but drastically reduced in plants overexpressing OsWOX4. The expression of genes responsible for auxin biosynthesis and transport was also changed in OsWOX4 transgenic lines. Transient transcriptional activation and electrophoretic mobility shift assays showed that OsWOX4 directly regulated the transcription of OsAUX1 through binding to its promoter region. Collectively, our results indicated that OsWOX4 played a crucial role in the primary root elongation by regulating auxin transport, suggesting its importance in rice root system architecture.

中文翻译：

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WUSCHEL相关同源框转录因子OsWOX4通过激活水稻OsAUX1控制初生根伸长

初生根是根系的基本组成部分，在水稻早期幼苗生长和成活中起着关键作用。然而，初生根伸长的分子机制仍有待深入了解。在这里，我们发现 OsWOX4 是一种与 WUSCHEL 相关的同源盒 (WOX) 转录因子，参与了水稻的初生根伸长。通过 RNA 干扰 (RNAi) 沉默 OsWOX4 大大增加了初生根长度，而其过表达显着降低了初生根伸长率。此外，与野生型相比，RNAi 根尖成熟区的分生组织大小和表皮细胞长度显着增加，而在过表达系中它们显着减少。进一步分析表明，游离 IAA 在 RNAi 根中的积累略有增加，但在过表达 OsWOX4 的植物中急剧减少。在 OsWOX4 转基因品系中，负责生长素生物合成和运输的基因的表达也发生了变化。瞬时转录激活和电泳迁移率变化分析表明 OsWOX4 通过与其启动子区域结合直接调节 OsAUX1 的转录。总的来说，我们的结果表明 OsWOX4 通过调节生长素转运在初生根伸长中起关键作用，表明其在水稻根系结构中的重要性。瞬时转录激活和电泳迁移率变化分析表明 OsWOX4 通过与其启动子区域结合直接调节 OsAUX1 的转录。总的来说，我们的结果表明 OsWOX4 通过调节生长素转运在初生根伸长中起关键作用，表明其在水稻根系结构中的重要性。瞬时转录激活和电泳迁移率变化分析表明 OsWOX4 通过与其启动子区域结合直接调节 OsAUX1 的转录。总的来说，我们的结果表明 OsWOX4 通过调节生长素转运在初生根伸长中起关键作用，表明其在水稻根系结构中的重要性。