Abstract
Abscisic acid (ABA) regulates various developmental processes and stress responses in plants. Protein phosphorylation/dephosphorylation is a central post-translational modification (PTM) in ABA signaling. However, the phosphoproteins regulated by ABA under osmotic stress remain unknown in maize. In this study, maize mutant vp5 (deficient in ABA biosynthesis) and wild-type Vp5 were used to identify leaf phosphoproteins regulated by ABA under osmotic stress. Up to 4052 phosphopeptides, corresponding to 3017 phosphoproteins, were identified by Multiplex run iTRAQ-based quantitative proteomic and LC-MS/MS methods. The 4052 phosphopeptides contained 5723 non-redundant phosphosites; 512 phosphopeptides (379 in Vp5, 133 in vp5) displayed at least a 1.5-fold change of phosphorylation level under osmotic stress, of which 40 shared common in both genotypes and were differentially regulated by ABA. Comparing the signaling pathways involved in vp5 response to osmotic stress and those that in Vp5, indicated that ABA played a vital role in regulating these pathways related to mRNA synthesis, protein synthesis and photosynthesis. Our results provide a comprehensive dataset of phosphopeptides and phosphorylation sites regulated by ABA in maize adaptation to osmotic stress. This will be helpful to elucidate the ABA-mediate mechanism of maize endurance to drought by triggering phosphorylation or dephosphorylation cascades.
Highlights
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Osmotic stress and control iTRAQ ratios for each run were converted to z-scores to normalize the data (Fig. 3), resulting in the identification of 4052 unique phosphopeptides at a false discovery rate (FDR) of 5%
There had been no comprehensive survey of phosphorylation sites regulated by Abscisic acid (ABA) in maize exposed to osmotic stress
Summary
The motifs SP and TP were common in both genotypes response to osmotic stress; 12 motifs were only predicted in Vp5; 2 motifs were only predicated in vp[5] (Table 3) These results indicated a high sensitivity and specificity of phosphorylation sites in maize response to ABA under osmotic stress. 34 phosphoproteins (Table 4) were found to contain several phosphopeptides These peptides had specific phosphorylation characteristics in response to ABA and osmotic stress. The different phosphopeptides of the other 19 phosphoproteins had similar response to ABA under osmotic stress Overall, this result showed the diversity of the phosphorylation sites and their specificity in maize response to ABA and stress treatments
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