Boron deficiency increases expressions of asparagine synthetase, glutamate dehydrogenase and glutamine synthetase genes in tobacco roots irrespective of the nitrogen source

Figures & data

Figure 1 Quantitative real-time polymerase chain reaction (PCR) analyses of root transcript levels for (A, B) Ntgdh-NAD;A1 and (C, D) Ntgdh-NAD;B2 genes of tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions. Plants were subjected (open bars) or not (filled bars) to a 24-h period of boron (B) deprivation from zero time. For more details see Materials and Methods. The results are given as means ± standard deviation (SD) (n = 6 separate plants). Asterisks indicate statistically significant differences between plants treated or not with B (Student’s t-test, *P < 0.05).

Figure 2 Quantitative real-time polymerase chain reaction (PCR) analyses of root transcript levels for (A, B) GLN1.5 and (C, D) AS genes of tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions. Plants were subjected (open bars) or not (filled bars) to a 24-h period of boron (B) deprivation from zero time. For more details see Materials and Methods. The results are given as means ± standard deviation (SD) (n = 6 separate plants). Asterisks indicate statistically significant differences between plants treated or not with B (Student’s t-test, *P < 0.05).

Figure 3 Effects of boron (B) deficiency on root nitrate and ammonium concentrations in tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions. Root concentrations of (A, B) nitrate and (C, D) ammonium were determined in plants subjected (open bars) or not (filled bars) to a 24-h period of B deprivation from zero time. The results are given as means ± standard deviation (SD) (n = 5 separate plants). Asterisks indicate statistically significant differences between plants treated or not with B (Student’s t-test, *P < 0.05). DW, dry weight.

Figure 4 Effects of boron (B) deficiency on several root amino acid concentrations in tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions. Root concentrations of (A, B) asparagine, (C, D) glutamine, (E, F) aspartate and (G, H) glutamate were determined in plants subjected (open bars) or not (filled bars) to a 24-h period of B deprivation from zero time. The results are given as means ± standard deviation (SD) (n = 5 separate plants). Asterisks indicate statistically significant differences between plants treated or not with B (Student’s t-test, *P < 0.05). DW, dry weight.

Figure 5 Effects of boron (B) deficiency on several root carbohydrates in tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions. Root concentrations of (A, B) glucose, (C, D) fructose, (E, F) sucrose and (G, H) total soluble carbohydrates (glucose, fructose and sucrose) were determined in plants subjected (open bars) or not (filled bars) to a 24-h period of B deprivation along two nitrogen-source transitions. The results are given as means ± standard deviation (SD) (n = 5 separate plants). Asterisks indicate statistically significant differences between plants treated or not with B (Student’s t-test, *P < 0.05). DW, dry weight.

Figure 6 Proposed model for the short-term response of roots of tobacco (Nicotiana tabacum, cv Gatersleben) plants to boron (B) deficiency. Dashed lines indicate processes that are directly or indirectly favored by B deficiency. For more details see text. AS, asparagine synthetase; GDH, glutamate dehydrogenase; GOGAT, glutamate synthase; GS, glutamine synthetase; NH₄⁺, ammonium.

Table 1 Effects of boron (B) deficiency on the concentration ratios between ammonium and hexoses (glucose plus fructose) in roots of tobacco (Nicotiana tabacum, cv Gatersleben) plants grown under two nitrogen-source transitions

		Ammonium/hexose ratioTime after B treatments (hours)
Nitrogen transition	Boron treatment	0	4	8	24
Nitrate-Ammonium	+B	0.420 ± 0.009	1.086 ± 0.102	1.714 ± 0.150	1.706 ± 0.110
Nitrate-Ammonium	−B	0.420 ± 0.009	2.194 ± 0.174	2.065 ± 0.112	7.143 ± 0.547
Ammonium-Nitrate	+B	0.723 ± 0.046	0.731 ± 0.051	0.472 ± 0.028	0.542 ± 0.072
Ammonium-Nitrate	−B	0.723 ± 0.046	0.702 ± 0.025	0.812 ± 0.039	1.044 ± 0.207

Mean values ± standard deviation (SD) for each nitrogen transition and B treatment were calculated from the respective root concentrations of ammonium, glucose and fructose shown in Fig. 3C, D and 5A–D.