Nitrate acts at the Arabidopsis thaliana shoot apical meristem to regulate flowering time

First author: Justyna Jadwiga Olas; Affiliations: Max Planck Institute of Molecular Plant Physiology (马克斯普朗克分子植物生理研究所): Potsdam, Germany

Corresponding author: Vanessa Wahl

Optimal timing of flowering, a major determinant for crop productivity, is controlled by environmental and endogenous cues. Nutrients are known to modify flowering time; however, our understanding of how nutrients interact with the known pathways, especially at the shoot apical meristem (SAM), is still incomplete. Given the negative side‐effects of nitrogen fertilization, it is essential to understand its mode of action for sustainable crop production. We investigated how a moderate restriction by nitrate is integrated into the flowering network at the SAM, to which plants can adapt without stress symptoms. This condition delays flowering by decreasing expression of SUPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) at the SAM. Measurements of nitrate and the responses of nitrate‐responsive genes suggest that nitrate functions as a signal at the SAM. The transcription factors NIN‐LIKE PROTEIN 7 (NLP7) and NLP6, which act as master regulators of nitrate signaling by binding to nitrate‐responsive elements (NREs), are expressed at the SAM and flowering is delayed in single and double mutants. Two upstream regulators of SOC1 (SQUAMOSA PROMOTER BINDING PROTEIN‐LIKE3 (SPL3) and SPL5) contain functional NREs in their promoters. Our results point at a tissue‐specific, nitrate‐mediated flowering time control in Arabidopsis thaliana.

在最适的时间开花是决定作物产量的重要因素，由外部环境和植物内部信号共同控制。众所周知，营养元素能够改变植物的开花时间，但目前对于营养元素如何与已知的开花时间调控通路相互作用，尤其是在茎尖分生组织部位，还不清楚。考虑到施加氮肥对于植物开花会有副作用，我们理所应当的要了解其背后潜在的分子机制，以便能够实施可持续农业。作者研究了适度的氮限制是如何被整合进茎尖分生组织的开花网络中去的，以及哪些植物能够在不表现出胁迫症状下适应氮缺陷条件。氮缺陷会通过降低茎尖分生组织中SOC1基因的表达来延迟开花。硝酸盐的测量以及氮响应基因的应答说明硝酸盐在茎尖分生组织中作为信号分子发挥作用。转录因子NLP7和NLP6是硝酸盐信号的主要调控子，其能够结合到硝酸盐响应元件上，并且在茎尖分生组织中表达，并且单突或者双突的植株开花都出现了延迟。SOC1基因的两个上游调控基因SPL3和SPL3都在启动子区含有硝酸盐响应元件。本文的研究揭示了一个拟南芥中组织特异性、硝酸盐介导的开花时间调控机制。

doi: https://doi.org/10.1111/nph.15812

Journal: New Phytologist

Published online: April 17, 2019