Ethylene modulates wheat response to phosphate deficiency

Ethylene is involved in the response to P deficiency in some model plants such as Arabidopsis and rice, but its role in wheat remains unclear. Following our recent study demonstrating the role of differentially expressed genes encoding ethylene response factors (ERFs) in response to P starvation in wheat, this study aims to investigate remodeling of the ethylene pathway and the physiological roles of ethylene in wheat under P deficiency using transcriptome analysis and the addition of the exogenous ethylene analogue, ethephon, or ethylene inhibitors. ERFs with at least a 2-fold expression change upon P deficiency had a distribution biased towards chromosome 4B. A group of genes encoding aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase were up-regulated under P starvation, suggesting an increase in ACC and ethylene content, which was verified by biochemical measurements and gas chromatography-mass spectrometry analysis. Under P deficiency, both root and shoot biomass decreased with application of exogenous ethephon or ethylene inhibitors, while root fork numbers and root surface area decreased upon ethephon treatment. Phosphate (Pi) concentrations in roots and old leaves increased with ethephon treatment, and Pi redistribution in roots and younger leaves was altered under Pi starvation. Our findings can guide breeding of germplasm with high Pi efficiency.