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Promotion of BR Biosynthesis by miR444 Is Required for Ammonium-Triggered Inhibition of Root Growth.
Plant Physiology ( IF 7.4 ) Pub Date : 2019-12-23 , DOI: 10.1104/pp.19.00190
Xiaoming Jiao 1 , Huacai Wang 1 , Jijun Yan 2, 3 , Xiaoyu Kong 1, 4 , Yawen Liu 1, 4 , Jinfang Chu 3, 5 , Xiaoying Chen 1, 3, 6 , Rongxiang Fang 1, 3 , Yongsheng Yan 6, 7
Affiliation  

Rice (Oryza sativa), the staple food for almost half of the world's population, prefers ammonium (NH4 +) as the major nitrogen resource, and while NH4 + has profound effects on rice growth and yields, the underlying regulatory mechanisms remain largely unknown. Brassinosteroids (BRs) are a class of steroidal hormones playing key roles in plant growth and development. In this study, we show that NH4 + promotes BR biosynthesis through miR444 to regulate rice root growth. miR444 targeted five homologous MADS-box transcription repressors potentially forming homologous or heterogeneous complexes in rice. miR444 positively regulated BR biosynthesis through its MADS-box targets, which directly repress the transcription of BR-deficient dwarf 1 (OsBRD1), a key BR biosynthetic gene. NH4 + induced the miR444-OsBRD1 signaling cascade in roots, thereby increasing the amount of BRs, whose biosynthesis and signaling were required for NH4 + -dependent root elongation inhibition. Consistently, miR444-overexpressing rice roots were hypersensitive to NH4 + depending on BR biosynthesis, and overexpression of miR444's target, OsMADS57, resulted in rice hyposensitivity to NH4 + in root elongation, which was associated with a reduction of BR content. In summary, our findings reveal a cross talk mechanism between NH4 + and BR in which NH4 + activates miR444-OsBRD1, an undescribed BR biosynthesis-promoting signaling cascade, to increase BR content, inhibiting root elongation in rice.

中文翻译:

铵触发的根生长抑制需要miR444促进BR生物合成。

稻米(Oryza sativa)是世界近一半人口的主要食物,它更喜欢铵(NH4 +)作为主要的氮资源,尽管NH4 +对稻米的生长和产量产生了深远的影响,但其潜在的调控机制仍然未知。油菜素类固醇(BRs)是一类类固醇激素,在植物生长和发育中起关键作用。在这项研究中,我们表明NH4 +通过miR444促进BR生物合成来调节水稻根系生长。miR444靶向五个可能在水稻中形成同源或异源复合物的同源MADS-box转录阻遏物。miR444通过其MADS-box靶标正调控BR生物合成,该靶标直接抑制BR缺乏生物的关键基因BR缺陷矮人1(OsBRD1)的转录。NH4 +诱导根部miR444-OsBRD1信号传导级联,从而增加了BRs的数量,BRs的生物合成和信号传导是NH4 +依赖性根伸长抑制所必需的。一致地,miR444的高表达水稻根部对BR的生物合成敏感,对NH4 +敏感,miR444的靶标OsMADS57的过表达导致水稻对根伸长中的NH4 +敏感性较低,这与BR含量的降低有关。总之,我们的发现揭示了NH4 +与BR之间的串扰机制,其中NH4 +激活miR444-OsBRD1(一种未描述的BR生物合成促进信号传导级联反应),以增加BR含量,抑制水稻根系伸长。取决于BR的生物合成,过度表达miR444的水稻根部对NH4 +敏感,miR444的靶标OsMADS57的过表达导致水稻对根伸长的NH4 +敏感性较低,这与BR含量的降低有关。总而言之,我们的发现揭示了NH4 +与BR之间的串扰机制,其中NH4 +激活miR444-OsBRD1(一种未描述的BR生物合成促进信号传导级联),以增加BR含量,抑制水稻根系伸长。取决于BR的生物合成,过度表达miR444的水稻根部对NH4 +敏感,miR444的靶标OsMADS57的过表达导致水稻对根伸长的NH4 +敏感性较低,这与BR含量的降低有关。总而言之,我们的发现揭示了NH4 +与BR之间的串扰机制,其中NH4 +激活miR444-OsBRD1(一种未描述的BR生物合成促进信号传导级联),以增加BR含量,抑制水稻根系伸长。
更新日期:2020-03-03
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