来源：X-MOL
Lanthanum, a rare earth element that is relatively common in the earth's crust. Its role in plant-pathogen interactions, particularly with root-knot nematodes, remains to be investigated. To address this lack of knowledge, tomato plants were treated with different concentrations of LaCl3 (20 μM, 40 μM, 60 μM, and 100 μM), and the day after, they were inoculated with root-knot nematode. The highest reduction in the number of galls and nematodes was recorded when LaCl3 was treated at a concentration of 100 μM, and the experiment was repeated twice independently. The time line monitoring of LaCl3 effect on antioxidant activity at 24, 48 and 72 hours post-inoculation (hpi) (in five replicates) showed a significant rise in antioxidant activity, including catalase, peroxidase, and superoxide dismutase, and a decrease in H2O2 accumulation at 72 hpi, which was further investigated by analysis of expression of respective genes. Additionally, expression analysis of phytohormones signaling markers revealed a significant upregulation of ethylene marker upon LaCl3 treatment. This was further validated by performing a susceptibility assay on plants deficient in ethylene accumulation, specifically ACC deaminase (ACCD) transgenic plants, which did not exhibit LaCl3-mediated resistance. Finally, expression levels of calmodulin genes were assessed locally in galls formed by the root-knot nematode, and it was found that they were highly modulated. These expression changes highlight the diverse roles and importance of calmodulin genes in the early defense responses of tomato plants to infection by root-knot nematode.