title: Comparative analysis of salt-responsive phosphoproteins in maize leaves using Ti(4+)--IMAC enrichment and ESI-Q-TOF MS.
abstract: Salinity is one of the most common abiotic stresses encountered by plants. Reversible protein phosphorylation is involved in plant defense processes against salinity stress. Here, we performed global phosphopeptide mapping through enrichment by our synthesized PVA-phosphate-Ti(4+)  IMAC coupled with subsequent identification by ESI-Q-TOF MS. A total of 104 peptide sequences containing 139 phosphorylation sites were determined from 70 phosphoproteins of the control leaves. In contrast, 124 phosphopeptides containing 143 phosphorylated sites from 92 phosphoproteins were identified in salt-stressed maize leaves. Compared with the control, 47 proteins were phosphorylated, 25 were dephosphorylated, and 45 overlapped. Among the 72 differential phosphoproteins, 35 were known salt stress response proteins and the rest had not been reported in the literature. To dissect the differential phosphorylation, gene ontology annotations were retrieved for the differential phosphoproteins. The results revealed that cell signaling pathway members such as calmodulin and 14-3-3 proteins were regulated in response to 24-h salt stress. Multiple putative salt-responsive phosphoproteins seem to be involved in the regulation of photosynthesis-related processes. These results may help to understand the salt-inducible phosphorylation processes of maize leaves.
authors.affiliation: Department of Environmental Sciences & Engineering, College of Resources and Environmental Sciences, China Agricultural University, Beijing, PR China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Hu
authors.forename: Shuangxi
authors.initials: S
authors.lastname: Guo
authors.forename: Xuexian
authors.initials: X
authors.lastname: Li
authors.forename: Xueqin
authors.initials: X
authors.lastname: Ren
mesh_terms: D000595:Amino Acid Sequence; D002846:Chromatography, Affinity / Q000379:methods*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020543:Proteome / Q000032:analysis / Q000737:chemistry / Q000187:drug effects; D055049:Salt Tolerance / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D014025:Titanium / Q000737:chemistry*; D003313:Zea mays / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D010940:Plant Proteins; D020543:Proteome; D012965:Sodium Chloride; D014025:Titanium