Phosphorus (P) is an essential nutrient for plant growth and productivity. Due to soil fixation, however, phosphorus availability in soil is rarely sufficient to sustain high crop yields. The overuse of fertilizers to circumvent the limited bioavailability of phosphate (Pi) has led to a scenario of excessive soil P in agricultural soils. Whereas adaptive responses to Pi deficiency have been deeply studied, less is known about how plants adapt to Pi excess and how Pi excess might affect disease resistance. We show that high Pi fertilization, and subsequent Pi accumulation, enhances susceptibility to infection by the fungal pathogen Magnaporthe oryzae in rice. This fungus is the causal agent of the blast disease, one of the most damaging diseases of cultivated rice worldwide. Equally, MIR399f overexpression causes an increase in Pi content in rice leaves, which results in enhanced susceptibility to M. oryzae. During pathogen infection, a weaker activation of defence‐related genes occurs in rice plants over‐accumulating Pi in leaves, which is in agreement with the phenotype of blast susceptibility observed in these plants. These data support that Pi, when in excess, compromises defence mechanisms in rice while demonstrating that miR399 functions as a negative regulator of rice immunity. The two signalling pathways, Pi signalling and defence signalling, must operate in a coordinated manner in controlling disease resistance. This information provides a basis to understand the molecular mechanisms involved in immunity in rice plants under high Pi fertilization, an aspect that should be considered in management of the rice blast disease.

中文翻译：

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磷酸盐过量会增加水稻对病原体感染的敏感性。

磷（P）是植物生长和生产力的必需营养素。然而，由于土壤固着，土壤中的磷有效性很少足以维持高作物产量。过度使用肥料来避免磷酸盐（Pi）有限的生物利用度，导致了农业土壤中土壤P过量的情况。尽管已经深入研究了对Pi缺乏的适应性反应，但对植物如何适应Pi过量以及Pi过量如何影响抗病性的了解还很少。我们表明，高磷肥和随后的磷积累，提高了水稻中真菌病原体稻瘟病菌感染的易感性。这种真菌是稻瘟病的病原体，稻瘟病是全世界栽培稻中最具破坏性的疾病之一。同样，MIR399f过表达会导致水稻叶片中的Pi含量增加，从而导致对米曲霉的敏感性增加。在病原体感染期间，过量积累叶片中Pi的水稻植物中防御相关基因的激活较弱，这与在这些植物中观察到的爆炸敏感性表型一致。这些数据表明，Pi过量时会损害水稻的防御机制，同时证明miR399可以作为水稻免疫力的负调节剂。Pi信号传导和防御信号传导这两个信号传导途径必须以协调的方式运行以控制疾病的抵抗力。该信息为了解高磷施肥下水稻植物免疫力涉及的分子机制提供了基础，这是应对稻瘟病的一个方面。