Abstract
abscisic acid (ABA) is a key phytohormone regulating plant development and stress response. The signal transduction of ABA largely relies on protein phosphorylation. However; little is known about the phosphorylation events occurring during ABA signaling in rice thus far. By employing a label-free; MS (Mass Spectrometry)-based phosphoproteomic approach; we identified 2271 phosphosites of young rice seedlings and their intensity dynamics in response to ABA; during which 1060 proteins were found to be differentially phosphorylated. Western-blot analysis verified the differential phosphorylation pattern of D1, SMG1 and SAPK9 as indicated by the MS result; suggesting the high reliability of our phosphoproteomic data. The DP (differentially phosphorylated) proteins are extensively involved in ABA as well as other hormone signaling pathways. It is suggested that ABA antagonistically regulates brassinosteroid (BR) signaling via inhibiting BR receptor activity. The result of this study not only expanded our knowledge of rice phosphoproteome, but also shed more light on the pattern of protein phosphorylation in ABA signaling.
Highlights
Abscisic acid (ABA) is an isoprenoid hormone playing critical roles in various plant biological processes
We focused on the profiling of young rice seedling phosphosites, phosphopeptides and phosphorylation intensity dynamics in response to ABA by employing a label-free, MS-based phosphoproteomic approach, and aimed to reveal the biological significance of protein phosphorylation in ABA signaling from the phosphoproteomic data
Peptides and sites is fundamental and crucial to understand the roles of protein phosphorylation in ABA signaling in rice
Summary
Abscisic acid (ABA) is an isoprenoid hormone playing critical roles in various plant biological processes. PYR (PYrabactin Resistance 1)/PYL (PYR1-like)/RCAR (Regulatory Components of ABA Receptor) are water soluble ligand-binding proteins belonging to START (star-related lipid-transfer)-domain superfamily, and have been shown to be ABA receptors by two independent research groups [5,6]. PYR/PYL/RCAR harbors binding sites for PP2Cs (2C-type protein phosphatase), which are negative regulators in ABA signaling. SnRK2s (SNF1-related protein kinases 2) are plant specific serine/threonine protein kinases bridging the ABA signal transduction from PP2Cs to the downstream ABA-responsive element (ABRE)-binding protein as well as other downstream components [7]. Upon the signal perception of ABA accumulation induced by stresses, PYR/PYL/RCAR competitively bind with PP2Cs to release the SnRK2s from PP2Cs. Subsequently, autophosphorylation of the released SnRK2s activates their own kinase activity and transmits the ABA signal to downstream ARFs, and thereby promotes the ABA or stress responses [3,8]
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