Nitrate can act as a potent signal to control growth and development in plants. In this study, we show that nitrate is able to stimulate primary root growth via increased meristem activity and cytokinin signaling. Cytokinin perception and biosynthesis mutants displayed shorter roots as compared with wild-type plants when grown with nitrate as the only nitrogen source. Histological analysis of the root tip revealed decreased cell division and elongation in the cytokinin receptor double mutant ahk2/ahk4 as compared with wild-type plants under a sufficient nitrate regime. Interestingly, a nitrate-dependent root growth arrest was observed between days 5 and 6 after sowing. Wild-type plants were able to recover from this growth arrest, while cytokinin signaling or biosynthesis mutants were not. Transcriptome analysis revealed significant changes in gene expression after, but not before, this transition in contrasting genotypes and nitrate regimes. We identified genes involved in both cell division and elongation as potentially important for primary root growth in response to nitrate. Our results provide evidence linking nitrate and cytokinin signaling for the control of primary root growth in Arabidopsis thaliana.

中文翻译：

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初级根生长的硝酸盐诱导需要拟南芥中的细胞分裂素信号传导。

硝酸盐可以作为控制植物生长发育的有效信号。在这项研究中，我们表明硝酸盐能够通过增加的分生组织活性和细胞分裂素信号传导来刺激初级根的生长。当以硝酸盐为唯一氮源生长时，与野生型植物相比，细胞分裂素的感知和生物合成突变体显示出更短的根。根尖的组织学分析表明，与硝酸盐充足的野生型植物相比，细胞分裂素受体双重突变体ahk2 / ahk4的细胞分裂和伸长减少。有趣的是，在播种后的第5天到第6天之间观察到了硝酸盐依赖性根生长停滞。野生型植物能够从这种生长停滞中恢复过来，而细胞分裂素信号传导或生物合成突变体则不能。转录组分析显示，在相反的基因型和硝酸盐机制转变之后（但不是之前），基因表达发生了显着变化。我们确定参与细胞分裂和伸长的基因对于响应硝酸盐的初级根生长潜在重要。我们的结果提供了证据，将硝酸盐和细胞分裂素信号传导联系起来，以控制拟南芥中的初生根生长。