Large-scale Proteomics Combined with Transgenic Experiments Demonstrates An Important Role of Jasmonic Acid in Potassium Deficiency Response in Wheat and Rice.

Potassium (K) is the most abundant inorganic cation in plants, and molecular dissection of K deficiency has received considerable interest in order to minimize K fertilizer input and develop high quality K-efficient crops. However, the molecular mechanism of plant responses to K deficiency is still poorly understood. In this study, 2-week-old bread wheat seedlings grown hydroponically in Hoagland solution were transferred to K-free conditions for 8 d, and their root and leaf proteome profiles were assessed using the iTRAQ proteome method. Over 4000 unique proteins were identified, and 818 K-responsive protein species showed significant differences in abundance. The differentially expressed protein species were associated with diverse functions and exhibited organ-specific differences. Most of the differentially expressed protein species related to hormone synthesis were involved in jasmonic acid (JA) synthesis and the upregulated abundance of JA synthesis-related enzymes could result in the increased JA concentrations. Abundance of allene oxide synthase (AOS), one key JA synthesis-related enzyme, was significantly increased in K-deficient wheat seedlings, and its overexpression markedly increased concentrations of K and JA, altered the transcription levels of some genes encoding K-responsive protein species, as well as enhanced the tolerance of rice plants to low K or K deficiency. Moreover, rice AOS mutant () exhibited more sensitivity to low K or K deficiency. Our findings could highlight the importance of JA in K deficiency, and imply a network of molecular processes underlying plant responses to K deficiency.