Phosphoproteomic Approaches to Evaluate ABA Signaling.

Abscisic acid (ABA) is a major phytohormone that regulates various processes in plants (e.g., seed dormancy/germination, abiotic/biotic stress responses). As protein phosphorylation is involved in the major pathways of ABA signaling, it is necessary to elucidate the phosphosignaling pathway involved in the ABA response. Phosphoproteomics enables determination of the proteins phosphorylated in vivo, and recent studies have applied a comparative phosphoproteomic approach to analyze ABA signaling in plants. For example, ABA-responsive phosphoproteins were identified in barley embryos. Furthermore, a phosphoproteomic approach is useful for screening protein kinase substrates by comparative analysis using kinase knockout mutants. Here, some technical points regarding phosphoproteomic analyses of ABA responses in plants are described.