SRA

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. Fertilizers are widely used to circumvent the limited bioavailability of phosphate (Pi) which 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. Here, we show that high Pi fertilization in rice plants, and subsequent Pi accumulation in leaves, enhances susceptibility to infection by Magnaporthe oryzae, the causal agent of the rice blast disease. 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 defense-related genes occurs in rice plants accumulating Pi in leaves, a response that is in agreement with the phenotype of blast susceptibility observed in these plants. These data support that Pi, when in excess, compromises defense mechanisms in rice while demonstrating that miR399 functions as a negative regulator of rice immunity. The two signaling pathways, Pi signaling and defense signaling, 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 grown under a high Pi fertilization regime, an aspect that should be considered in management of the rice blast disease Overall design: 12 samples in total: 1 wild-type (WT) and 2 miR399f overexpressing lines (L4, L20) with 2 treatments (Control, Infected), 2 biological replicates each. Samples are: C-WT, C-L4, C-L20 (Control); I-WT, I-L4, I-L20 (Infected)