Table 1.
Partial list of phosphopeptides significantly altered in response to ABA treatment (50 μM for 5, 15, or 30 min)
| Average phosphorylation change with ABA | |||||
| ATG accession | Protein | Phosphopeptide | 5 min | 15 min | 30 min |
| Aquaporins | |||||
| AT3G53420, AT2G37170 | Plasma membrane intrinsic protein 2-A/B (PIP2-A/B) | K.SLGS*FRS*AANV.- | N/a | N/a | Decrease (76%) CID/ETD |
| AT4G35100 | Plasma membrane intrinsic protein 3 (PIP3) | K.ALGS*FRS*NATN.- | Decrease (26%) | Decrease (16%) | Decrease (59%) CID/ETD |
| AT2G16850 | Plasma membrane intrinsic protein 2–8 (PIP2-8) | K.ALAS*FRS*NPTN.- | Decrease (36%) | No change | Decrease (19%) ETD |
| AT5G60660 | Plasma membrane intrinsic protein 2–4 (PIP2-4) | K.ALGSFGSFGS*FR.S | No change | No change | Decrease (43%) CID/ETD |
| SnRK2 kinases | |||||
| AT4G33950 | SnRK2.6/OST1 kinase | K.S*TVGTPAYIAPEVLLK.K | N/a | N/a | Increase (358%) ETD |
| AT3G50500 | SnRK2.2 kinase | K.STVGTPAYIAPEILLRQEYDGK.L | N/a | N/a | Increase (493%) ETD |
| AT5G66880 | SnRK2.3 kinase | K.S*TVGTPAYIAPEVLLRQEYDGK.I | N/a | N/a | Increase (124%) ETD |
| AT1G10940 | SnRK2.4 kinase | K.STVGTPAYIAPEVLSRREYDGK.M | N/a | N/a | Increase (239%) ETD |
| Transcription factors | |||||
| AT1G45249, AT1G49720, AT4G34000, AT3G19290, AT3G56850 | ABA-responsive elements-binding factor 2 (ABF2) | R.QGS*LTLPR.T | N/a | N/a | Increase (106%) |
| AT3G56850 | ABA-responsive element binding protein 3 (AREB3) | R.QSS*LYSLTLDEVQNHLGSSGK.A | N/a | N/a | Increase (112%) |
| AT2G21230 | bZIP family transcription factor | R.SIS*GEDTSDWSNLVK.K | Increase (135%) | N/a | N/a |
| AT2G21230 | bZIP family transcription factor | R.SISGEDTSDWSNLVK.K | Increase (214%) | Increase (108%) | N/a |
| AT1G15750 | Topless transcription repressor (TPL) | R.APS*PVNNPLLGGIPK.A | Decrease (18%) | No change | Decrease (69%) |
| Calcium-related | |||||
| AT2G32450 | Calcium-binding EF hand family protein | R.DNNVPVSYS*GNGIPTK.S | No change | No change | Decrease (30%) |
| AT1G20760 | Calcium-binding EF hand family protein | K.S*QDGDYFGSGDDFGGNTAR.A | No change | Decrease (113%) | Decrease (49%) |
| AT1G09210 | Calreticulin-2 (CRT2) | K.DAPAES*DAEDEPEDDEGGDDSDSESKAEETK.S | N/a | Decrease (10%) | Decrease (33%) |
| AT4G35310; AT2G17290 | Calcium-dependent protein kinase 5/6 (CPK5/6) | K.NSLNIS*MR.D | Decrease (72%) | Decrease (22%) | N/a |
| AT1G19870 | IQ-domain 32 (IQD32) | R.KVS*NPSFIAAQSK.F | N/a | N/a | Decrease (66%) |
| AT1G19870 | IQ-domain 32 (IQD32) | K.GTETEEDDLIGTELQGPSAADAAK.I | Decrease (92%) | No change | N/a |
| Drought or ABA responsive | |||||
| AT1G76180 | Early response to dehydration 14 (ERD14) | K.VHIS*EPEPEVK.H | N/a | N/a | Decrease (78%) |
| AT5G40390 | Seed imbibition 1-like (SIP1) | K.SDS*GINGVDFTEK.F | N/a | N/a | Decrease (117%) CID/ETD |
| AT2G25070 | Protein phosphatase 2C (PP2C) | K.KPNPSETEPEDSKPEPSEDEPSSSS.- | Decrease (59%) | Decrease (14%) | Decrease (23%) |
Confirmed sites of phosphorylation are shown in bold followed by (*) as verified by manual MS2 inspection. Ambiguous sites of phosphorylation are denoted by italics. Phosphorylation changes are presented as the average percent change of the treated sample relative to control with three technical replicates each, with significance (P < 0.05) as determined by two-tailed t test. Unless otherwise denoted, identifications were made by CID fragmentation. N/a, not applicable.