Article Figures & Data
Figures
- Figure 1.
Cytokinin-Mediated Delay in Senescence Correlates with an Increase in the Activity of Extracellular Invertase.
Extracellular invertase activity has been determined in top, middle, and bottom leaves of tobacco plants expressing the ipt gene under control of the senescence-activated promoter SAG12 (SAG12:ipt; Gan and Amasino, 1995) and of wild-type plants (W38). Bars represent the mean value of three independent replications ± se. DW, dry weight.
- Figure 2.
Senescence-Induced Expression of Extracellular Invertase Cin1 Results in a Delay of Senescence.
(A) Phenotype of the transgenic SAG12:Cin1 and of the wild-type (W38) tobacco plants 17 weeks after sawing. The transgenic plants show a delay in senescence of mature leaves in respect to the loss of mature leaves in the wild-type plants.
(B) Delay in senescence of detached young leaves from the transgenic SAG12:Cin1 and wild-type (W38) tobacco plants incubated in the light for 4 weeks.
The results have been reproduced in five independent experiments with three independent transgenic lines, and representative results obtained with line NT58-5 are shown.
- Figure 3.
The Increase in Extracellular Invertase Activity in Transgenic Tobacco Plants Expressing Extracellular Invertase under Control of the Senescence-Activated Promoter SAG12 Is Specific and Does Not Result in an Increased Glucose Concentration.
(A) Extracellular invertase activity measured in bottom and top leaves of SAG12:Cin1 and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean value of three independent replications ± se.
(B) Vacuolar invertase activity measured in bottom and top leaves of SAG12:Cin1 and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean value of three independent replications ± se.
(C) Glucose contents of bottom and top leaves of SAG12:Cin1 and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean of three independent replication leaves ± se.
The results have been reproduced with three independent transgenic lines, and representative results obtained with line NT58-5 are shown.
- Figure 4.
Chemical Induction of Extracellular Invertase Cin1 Results in Delay of Senescence.
(A) Effect of the infiltration of tetracycline into detached leaves of a transgenic line expressing the extracellular invertase Cin1 under control of the tetracycline-inducible TetR promoter. The left leaf was infiltrated with an MS control solution, whereas the right one was infiltrated with the same solution containing tetracycline at a final concentration of 10 μg/L.
(B) Chlorophyll fluorescence image of the leaves shown in (A).
(C) RNA gel blot showing the accumulation of the Cin1 transcripts in leaves after 2 h of treatment with tetracycline in comparison to control leaves.
(D) Effect of the localized induction of Cin1 by spotting chlorotetracycline onto transgenic leaves. An MS solution containing either 0.02% Silwet (left control leaf) or the detergent plus chlorotetracycline (10 μg/L) (right leaf) was spotted onto the marked zones.
The results have been reproduced in five independent experiments with three independent transgenic lines, and representative results obtained with line NT35-7 are shown.
- Figure 5.
Effect of the Inhibition of Extracellular Invertase Activity on the Delay of Senescence by Kinetin.
(A) Detached leaves of a transgenic tobacco line expressing the tobacco invertase inhibitor P17A under control of the cytokinin-inducible promoter Lin6 (Lin6:P17A) and wild-type plants (W38) were infiltrated with water containing kinetin at a final concentration of 30 μg/L.
(B) RNA gel blot analysis showing the accumulation of the transcripts for extracellular invertase Ntβfruct1 and the invertase inhibitor P17A in wild-type (W38) and transgenic (Lin6:P17A) plants after 1 and 3 d of treatment with kinetin (K), respectively.
The results have been reproduced in five independent experiments with three independent transgenic lines, and representative results obtained with line NT71-29 are shown.
Tables
- Table 1.
Kinetin Induction of the Invertase Inhibitor P17A Results in Inhibition of Sucrose Cleavage
Line Time Treatment Glucose (mM/gFW) Fructose (mM/gFW) Sucrose (mM/gFW) W38 1 d None 19.2 (2.4) 13.5 (1.6) 6.7 (1.2) Kinetin 19.7 (2.9) 18.5 (2.8) 9.1 (1.7) 3 d None 42.5 (0.4) 41.3 (1.2) 9.0 (4.4) Kinetin 47.5 (1.7) 46.7 (1.7) 9.1 (2.4) Lin6:P17A 1 d None 14.0 (6.1) 11.6 (5.8) 8.1 (2.1) Kinetin 6.0 (1.3) 4.2 (1.6) 6.6 (1.9) 3 d None 46.5 (3.5) 33.9 (2.4) 8.8 (0.1) Kinetin 19.9 (5.6) 20.1 (5.4) 9.1 (2.6) Detached leaves of a transgenic tobacco line expressing the tobacco invertase inhibitor P17A under control of the cytokinin-inducible promoter Lin6 (Lin6:P17A) and wild-type plants (W38) were infiltrated with water containing kinetin at a final concentration of 30 μg/L, and concentrations of soluble sugars have been determined. The values represent the mean value of three independent replications ± se obtained with line NT71-29. Similar results have been obtained with line NT71-9.
Supplemental Data
Files in this Data Supplement:
- Supplemental Figure 1 - Senescence-induced expression of extracellular invertase Cin1 results in a delay of senescence in transgenic lines lines NT58-15 and NT58-69. (A) Phenotype of the transgenic SAG12:Cin1 (NT58-15 and NT58-69) and of wild-type (W38) tobacco plants 7 weeks after sawing. The transgenic plants show a delay in senescence of mature leaves with respect to the loss of mature leaves in the wild-type plants. (B) Delay in senescence of detached young leaves from transgenic SAG12:Cin1 (NT58-15 and NT58-69) and wild-type (W38) tobacco plants incubated in the light for 4 weeks. The results have been reproduced in three independent experiments.
- Supplemental Figure 2 - The increase in extracellular invertase activity in transgenic tobacco plants expressing extracellular invertase under control of the senescence-activated promoter SAG12 is specific and does not result in an increased glucose concentration. (A) Extracellular invertase activity measured in bottom and top leaves of SAG12:Cin1 (NT58-15 and NT58-69) and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean value of three independent replications +/- SE. (B) Vacuolar invertase activity measured in bottom and top leaves of SAG12:Cin1 (NT58-15 and NT58-69) and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean value of three independent replications +/- SE. (C) Glucose contents of bottom and top leaves of SAG12:Cin1 (NT58-15 and NT58-69) and wild-type (W38) plants 17 weeks after sawing. Bars represent the mean of three independent replications leaves +/- SE.
