College of Life Science, Shandong Normal University, Jinan 250014, China.
Crop Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China.
Int J Mol Sci. 2024 Sep 3;25(17):9566. doi: 10.3390/ijms25179566.
The lateral root (LR) is an essential component of the plant root system, performing important functions for nutrient and water uptake in plants and playing a pivotal role in cereal crop productivity. Nitrate (NO) is an essential nutrient for plants. In this study, wheat plants were grown in 1/2 strength Hoagland's solution containing 5 mM NO (check; CK), 0.1 mM NO (low NO; LN), or 0.1 mM NO plus 60 mg/L 2,3,5-triiodobenzoic acid (TIBA) (LNT). The results showed that LN increased the LR number significantly at 48 h after treatment compared with CK, while not increasing the root biomass, and LNT significantly decreased the LR number and root biomass. The transcriptomic analysis showed that LN induced the expression of genes related to root IAA synthesis and transport and cell wall remodeling, and it was suppressed in the LNT conditions. A physiological assay revealed that the LN conditions increased the activity of IAA biosynthesis-related enzymes, the concentrations of tryptophan and IAA, and the activity of cell wall remodeling enzymes in the roots, whereas the content of polysaccharides in the LRP cell wall was significantly decreased compared with the control. Fourier-transform infrared spectroscopy and atomic microscopy revealed that the content of cell wall polysaccharides decreased and the cell wall elasticity of LR primordia (LRP) increased under the LN conditions. The effects of LN on IAA synthesis and polar transport, cell wall remodeling, and LR development were abolished when TIBA was applied. Our findings indicate that NO starvation may improve auxin homeostasis and the biological properties of the LRP cell wall and thus promote LR initiation, while TIBA addition dampens the effects of LN on auxin signaling, gene expression, physiological processes, and the root architecture.
侧根（LR）是植物根系的重要组成部分，在植物的养分和水分吸收中发挥重要作用，并在谷类作物生产力中起着关键作用。硝酸盐（NO）是植物的必需养分。在这项研究中，小麦植株在含有 5 mM NO（对照；CK）、0.1 mM NO（低 NO；LN）或 0.1 mM NO 加 60 mg/L 2,3,5-三碘苯甲酸（TIBA）（LNT）的 1/2 强度 Hoagland 溶液中生长。结果表明，与 CK 相比，LN 在处理后 48 小时显著增加了 LR 数量，而不增加根生物量，LNT 则显著减少了 LR 数量和根生物量。转录组分析表明，LN 诱导与根 IAA 合成和运输以及细胞壁重塑相关的基因表达，而在 LNT 条件下则受到抑制。生理测定表明，LN 条件下增加了 IAA 生物合成相关酶、色氨酸和 IAA 浓度以及细胞壁重塑酶的活性，而 LRP 细胞壁中多糖的含量与对照相比显著降低。傅里叶变换红外光谱和原子显微镜显示，在 LN 条件下，细胞壁多糖的含量降低，LR 原基（LRP）的细胞壁弹性增加。当应用 TIBA 时，LN 对 IAA 合成和极性运输、细胞壁重塑和 LR 发育的影响被消除。我们的研究结果表明，NO 饥饿可能通过改善 IAA 稳态和 LRP 细胞壁的生物学特性来促进 LR 的起始，而 TIBA 的添加则抑制了 LN 对生长素信号、基因表达、生理过程和根系结构的影响。
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