The stimulatory effect and mechanism of low-dose lanthanum on soybean leaf cells

Light rare earth elements (LREEs) have been long used in agriculture (i.e., mainly via aerially applied LREE fertilizers) based on the fact that low-dose LREEs promote plant growth. Meanwhile, the toxic effects of low-dose LREEs on organisms have also been found. However, the cellular and molecular mechanism of low-dose LREEs acting on organisms remain unclear. Plants are at the beginning of food chains, so it is critical to uncover the cellular and molecular mechanism of low-dose LREEs on plants. Here, lanthanum (La) and soybean were the representatives of LREEs and plants, respectively. The effects of low-dose La on soybean leaves were investigated, and the stimulatory effect and mechanism of low-dose LREEs on leaf cells were revealed. Specifically, clathrin-mediated endocytosis (CME) activated by low-dose La is an influx channel for La in soybean leaf cells. The intracellular La and La-activated CME jointly disturbed multiple forms of intracellular homeostasis, including metallic element homeostasis, redox homeostasis, gene expression homeostasis. The disturbed homeostasis either stimulated cell growth or caused damage to the plasma membrane of soybean leaf cells. These results provide new insights for clarifying the cellular and molecular mechanisms of low-dose LREEs as a class of stimulators instead of nutrients to stimulate plants.