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The identification of new cytosolic glutamine synthetase and asparagine synthetase genes in barley (Hordeum vulgare L.), and their expression during leaf senescence.

Avila-Ospina L, Marmagne A, Talbotec J, Krupinska K, Masclaux-Daubresse C - J. Exp. Bot. (2015)

Bottom Line: The three eukaryotic-like HvGS1_1, HvGS1_2, and HvGS1_3 sequences showed the typical senescence-induced reduction in gene expression described in many plant species.By contrast, the two prokaryotic-like HvGS1_4 and HvGS1_5 sequences were repressed by leaf senescence, similar to the HvGS2 gene, which encodes the chloroplast glutamine synthetase isoenzyme.Responses of the HvASN sequences to dark-induced senescence showed that there are two categories of asparagine synthetases, one induced in the dark and the other repressed by the same conditions.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR1318, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France.

No MeSH data available.


Glutamine synthetase (GS) activity and protein contents in leaf ranks of plants. (A) GS activity. Data are mean ±SD of 3–4 biological replicates. The asterisks (*) indicate the significant differences between leaf (n+1) and leaf (n) under the same nitrate conditions. The symbol (#) indicates significant differences between LN and HN for the same leaf rank. Significance was evaluated using a t test with P <0.05. LN (low nitrate; light grey) and HN (high nitrate; dark grey). (B) GS1 (39kDa) and GS2 (46kDa) were identified on Western blots. GS1 and GS2 proportions were calculated after quantification of signals using densitometry and ImageJ imaging software. Equal protein amounts were loaded in each lane. All experiments were performed on two different cultures giving the same results.
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Figure 4: Glutamine synthetase (GS) activity and protein contents in leaf ranks of plants. (A) GS activity. Data are mean ±SD of 3–4 biological replicates. The asterisks (*) indicate the significant differences between leaf (n+1) and leaf (n) under the same nitrate conditions. The symbol (#) indicates significant differences between LN and HN for the same leaf rank. Significance was evaluated using a t test with P <0.05. LN (low nitrate; light grey) and HN (high nitrate; dark grey). (B) GS1 (39kDa) and GS2 (46kDa) were identified on Western blots. GS1 and GS2 proportions were calculated after quantification of signals using densitometry and ImageJ imaging software. Equal protein amounts were loaded in each lane. All experiments were performed on two different cultures giving the same results.

Mentions: Carboxypeptidase, endopeptidase (pH 5.4 and pH 4.5), and GS activities are well-known markers of both leaf senescence and nitrogen remobilization. Both were monitored in leaf ranks from plants grown under LN and HN conditions. All activities were significantly higher in old leaves compared with young ones under both LN and HN (Figs 3, 4A). For the same leaf rank, the magnitude of protease activity was quite similar in the two nitrate conditions. By contrast, for L1 and L2, total GS activity was higher in the LN leaf compared with the corresponding HN leaf. Western blot analysis allowed the GS1 and GS2 isoform contents to be semi-quantified and to estimate their respective proportions (Fig. 4B). GS1 relative content increased with leaf ageing, especially in plants grown under HN (HNL1 and HNL2 compared with HNL3 and HNL4). The relative content of GS1 was already high (60%) in young leaves of LN-grown plants, suggesting that HvGS1 expression is higher under LN compared with HN, which was confirmed subsequently for the HvGS1_1 gene (see below).


The identification of new cytosolic glutamine synthetase and asparagine synthetase genes in barley (Hordeum vulgare L.), and their expression during leaf senescence.

Avila-Ospina L, Marmagne A, Talbotec J, Krupinska K, Masclaux-Daubresse C - J. Exp. Bot. (2015)

Glutamine synthetase (GS) activity and protein contents in leaf ranks of plants. (A) GS activity. Data are mean ±SD of 3–4 biological replicates. The asterisks (*) indicate the significant differences between leaf (n+1) and leaf (n) under the same nitrate conditions. The symbol (#) indicates significant differences between LN and HN for the same leaf rank. Significance was evaluated using a t test with P <0.05. LN (low nitrate; light grey) and HN (high nitrate; dark grey). (B) GS1 (39kDa) and GS2 (46kDa) were identified on Western blots. GS1 and GS2 proportions were calculated after quantification of signals using densitometry and ImageJ imaging software. Equal protein amounts were loaded in each lane. All experiments were performed on two different cultures giving the same results.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4378633&req=5

Figure 4: Glutamine synthetase (GS) activity and protein contents in leaf ranks of plants. (A) GS activity. Data are mean ±SD of 3–4 biological replicates. The asterisks (*) indicate the significant differences between leaf (n+1) and leaf (n) under the same nitrate conditions. The symbol (#) indicates significant differences between LN and HN for the same leaf rank. Significance was evaluated using a t test with P <0.05. LN (low nitrate; light grey) and HN (high nitrate; dark grey). (B) GS1 (39kDa) and GS2 (46kDa) were identified on Western blots. GS1 and GS2 proportions were calculated after quantification of signals using densitometry and ImageJ imaging software. Equal protein amounts were loaded in each lane. All experiments were performed on two different cultures giving the same results.
Mentions: Carboxypeptidase, endopeptidase (pH 5.4 and pH 4.5), and GS activities are well-known markers of both leaf senescence and nitrogen remobilization. Both were monitored in leaf ranks from plants grown under LN and HN conditions. All activities were significantly higher in old leaves compared with young ones under both LN and HN (Figs 3, 4A). For the same leaf rank, the magnitude of protease activity was quite similar in the two nitrate conditions. By contrast, for L1 and L2, total GS activity was higher in the LN leaf compared with the corresponding HN leaf. Western blot analysis allowed the GS1 and GS2 isoform contents to be semi-quantified and to estimate their respective proportions (Fig. 4B). GS1 relative content increased with leaf ageing, especially in plants grown under HN (HNL1 and HNL2 compared with HNL3 and HNL4). The relative content of GS1 was already high (60%) in young leaves of LN-grown plants, suggesting that HvGS1 expression is higher under LN compared with HN, which was confirmed subsequently for the HvGS1_1 gene (see below).

Bottom Line: The three eukaryotic-like HvGS1_1, HvGS1_2, and HvGS1_3 sequences showed the typical senescence-induced reduction in gene expression described in many plant species.By contrast, the two prokaryotic-like HvGS1_4 and HvGS1_5 sequences were repressed by leaf senescence, similar to the HvGS2 gene, which encodes the chloroplast glutamine synthetase isoenzyme.Responses of the HvASN sequences to dark-induced senescence showed that there are two categories of asparagine synthetases, one induced in the dark and the other repressed by the same conditions.

View Article: PubMed Central - PubMed

Affiliation: INRA, UMR1318, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France.

No MeSH data available.