Table 2. Phosphorylation sites Identified within the sequence of SnRK2.4, SnRK2.10, and their putative interactors.

Identified phosphorylated Ser and Tyr (pS, pT) are denoted in bold. For each peptide the localization in the protein is indicated with its start and end position. Peptide expectation value is the number of times an equal or higher score could be expected to be obtained purely by chance. Site analysis % is the probability that the phosphorylation was assigned correctly to particular residue. Sequences of peptides marked with an asterisk were used for design of the synthetic peptides used for in vitro kinase activity assays. Spectrum number corresponds to spectra presented in Supplemental Figure S1.

Bait	Spectrum No.	Protein Name	Peptide Start	Peptide End	Peptide Ion Score	Peptide Expectation Value	Peptide Sequence	Phosphorylation Site Position in Protein Sequence	Site Analysis %	Phosphorylation Induced by Salt or Osmotic Stress Shown in
SnRK2.4	1	VCS	86	100	66.21	0.00002	TLSYPTPPLNLQpSPR	S98	99.98	–
	2	VCS	142	156	49.27	0.001	SFPGGSGPIRVPpSCK	S154	98.83	–
	3	VCS	637	662	109.64	0.000000001	TSGLPSQTSGAGSAYATLPQLPLpSPR *	S660	100.00	Stecker et al., 2014
	4	VCS	637	662	58.26	0.0002	pTSGLPSQTSGAGSAYATLPQLPLpSPR *	T637+S660	99.84	Stecker et al., 2014
	5	VCS	637	662	44.00	0.004	TSGLPSQTSGAGSApYATLPQLPLpSPR *	Y651+S660	98.77	Stecker et al., 2014
	6	VCS	637	666	72.12	0.00001	TSGLPSQTSGAGSAYATLPQLPLpSPRLpSSK *	S660+S664	86.13	Stecker et al., 2014
	7	VCS	690	699	66.86	0.00001	TPpSADYSVDR *	S692	99.76	Stecker et al., 2014
	8	VCS	821	835	77.59	0.000001	VFCSQVSNLpSTEMAR	S830	93.06	–
	9	VCS	821	835	80.73	0.000001	VFCSQVpSNLSTEMAR	S827	99.86	–
	10	VCS	1149	1163	60.41	0.0001	ESITSApSpSVAQALSR *	S1155 or S1156	49.95/49.95	Stecker et al., 2014; Maszkowska et al., 2019
	11	VCS	1171	1203	41.43	0.003	NLLALAAAGANSGGSNSLVpTQLpSGGPLGALLEK	S1193 or T1190	64.22/32.49	–
										–
	12	VCR	678	687	60.03	0.00004	TSpSADYFYVR *	S680	95.12	Stecker et al., 2014; Maszkowska et al., 2019
	13	VCR	708	730	62.81	0.0001	SKDTNVTPDDDVSGIRpSPSAFFK	S724	72.90	–
	14	VCR	708	730	76.19	0.000003	SKDTNVTPDDDVSGIRSPpSAFFK	S726	73.91	–
	15	VCR	807	823	46.77	0.002	ENIFCSQASNLpSTEMAR	S818	84.49	–
	16	VCR	862	877	64.88	0.00002	LPESGpSSSGLVATNSK	S867	87.00	–
	17	VCR	1174	1199	42.17	0.002	LALTAAGSNPLVTQLpSNGPLGALLEK	S1189	89.09	Maszkowska et al., 2019
	18	SnRK2.4	158	173	79.41	0.000001	pSpTVGTPAYIAPEVLSR	S158 or T159	49.93/49.93	Stecker et al., 2014
	19	SnRK2.4	350	361	49.63	0.001	TVKEVHApSGEVR	S357	99.88	–
SnRK2.10	20	VCS	86	100	84.61	0.0000003	TLSYPTPPLNLQpSPR	S98	100.00	–
										–
	21	VCS	637	662	97.59	0.00000002	TSGLPSQTSGAGSAYATLPQLPLpSPR *	S660	100.00	Stecker et al., 2014
	22	VCS	637	662	42.10	0.0065	TSGLPSQTSGAGSApYATLPQLPLpSPR *	Y651+S660	96.93	Stecker et al., 2014
	23	VCS	690	699	54.82	0.0001	TPpSADYSVDR *	S692	95.10	Stecker et al., 2014; Maszkowska et al., 2019
	24	VCS	821	835	72.76	0.000004	VFCSQVpSNLSTEMAR	S827	99.77	–
	25	VCS	821	835	75.56	0.000002	VFCSQVSNLpSTEMAR	S830	93.09	–
	26	VCS	1217	1233	42.39	0.005	LIpSERKYEESFTSALQR	S1219	99.90	–
	27	VCR	678	687	40.65	0.0034	TSpSADYFYVR *	S680	86.03	Stecker et al., 2014
	28	VCR	1213	1229	42.39	0.0049	LIpSERKYEESFTSALQR	S1215	99.90	–
	29	SnRK2.10	350	359	59.71	0.0001	QVHApSMGEVR	S354	100.00	–