Mineral nitrogen sources differently affect root glutamine synthetase isoforms and amino acid balance among organs in maize

Table 1 Spot assignments to the specific isoform of glutamine synthetase (GS) by LC-nESI-MS/MS

N	Acr	Protein AN	pI/MW(t)	pI/MW(e)	u.p. s/t	%Cov.	Avg n. p.
1	GS2a	Glutamine synthetase chloroplastic P25462	6.42/46.0	5.36/47.6	9/9	8.0 ± 2.4	3.2 ± 0.9
2	GS2b	Glutamine synthetase chloroplastic P25462	6.42/46.0	5.44/45.5	10/10	16.9 ± 1.3	6.7 ± 0.4
3	GS2c	Glutamine synthetase chloroplastic P25462	6.42/46.0	5.52/45.2	4/4	7.2 ± 0.6	2.7 ± 0.2
4*	GS1-3/4	Glutamine synthetase root isozyme 3 P38561	5.24/39.2	5.22/41.6	9/10	35.9 ± 1.8	8.4 ± 0.4
		Glutamine synthetase root isozyme 4 P38562	5.23/39.0		9/12
5	GS1-5	Glutamine synthetase root isozyme 5 P38563	5.52/39.3	5.40/39.4	6/14	44.3 ± 1.3	11.2 ± 0.2
6	GS1-1	Glutamine synthetase root isozyme 1 P38559	5.60/39.2	5.48/39.1	3/17	40.5 ± 1.8	11.2 ± 0.6

The different spots indicated in Figure 3 were separately collected from the root 2D profile of each nutritional treatment. Values are the mean ± SE of four independent biological samples (one per treatment) analysed in triplicate (n = 12). 4*: the spot was assigned as a co-migration of the GS1-3 and GS1-4 isoforms. N: spot number on Figure 3. Acr: acronym reported in Figure 4. AN: accession number. p I /MW are expressed in kDa and compare the theoretical values (t) with the experimental ones (e); u.p.: number of unique peptides identified, s: specific to the isoform, t: total. %Cov: amino acid coverage. Avg n. p.: number of distinct peptides. Detailed information on LC-nESI-MS/MS sequencing is reported in Additional file 1.

ISSN: 1471-2229