Key message

We reveal the onset and dynamic tissue-specific cytokinin signaling domains and functional importance of auxin in the auxin–cytokinin interaction domains in shaping root architecture in the economically important rice plant.

Abstract

Plant hormones such as auxin and cytokinin are central regulators of root organogenesis. Typical in the grass species, the root system in rice is primarily composed of post-embryonic adventitious/crown roots (ARs/CRs). Antagonistic auxin–cytokinin activities mutually balance each other to ensure proper root development. Cytokinin has been shown to inhibit crown root initiation in rice; albeit, the responsive domains remain elusive during the initiation and outgrowth of crown root primordia (CRP). Here, we show the cytokinin response domains during various stages of CRP development. RNA–RNA in situ hybridization and protein immunohistochemistry studies of the reporter gene expressed under the cytokinin responsive synthetic promoter revealed detailed spatio-temporal cytokinin signaling domains in the developing CRP. Furthermore, rice lines genetically depleted for endogenous auxin in the cytokinin responsive domains provided insight into the functional importance of auxin signaling during crown root development. Thus, our study demonstrates the onset and dynamic tissue-specific cytokinin response and functional significance of auxin–cytokinin interaction during root architecture formation in rice, a model grass species.

中文翻译：

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水稻冠根发育过程中细胞分裂素反应域中生长素的动态细胞分裂素信号及功能

关键信息

我们揭示了生长素-细胞分裂素相互作用结构域中生长素的起始和动态组织特异性细胞分裂素信号结构域以及在经济上具有重要意义的水稻植物根结构形成中的功能重要性。

抽象的

植物激素如生长素和细胞分裂素是根器官发生的中心调节剂。在禾本科植物中，水稻的根系主要由胚后不定根/冠根 (ARs/CRs) 组成。拮抗的生长素-细胞分裂素活性相互平衡，以确保适当的根发育。细胞分裂素已被证明可抑制水稻冠根的萌生；尽管如此，响应域在冠根原基（CRP）的起始和生长过程中仍然难以捉摸。在这里，我们展示了 CRP 发展不同阶段的细胞分裂素反应域。在细胞分裂素反应性合成启动子下表达的报告基因的 RNA-RNA 原位杂交和蛋白质免疫组织化学研究揭示了发育中的 CRP 中详细的时空细胞分裂素信号结构域。此外，细胞分裂素反应域中内源性生长素基因缺失的水稻品系提供了对生长素信号在冠根发育过程中的功能重要性的深入了解。因此，我们的研究证明了水稻（一种模式草种）根结构形成过程中生长素-细胞分裂素相互作用的起始和动态组织特异性细胞分裂素反应和功能意义。