-
[show abstract]
[hide abstract]
ABSTRACT: An ipt gene under control of the senescence-specific SAG12 promoter from Arabidopsis (P(SAG12)-IPT) significantly delayed developmental and postharvest leaf senescence in mature heads of transgenic lettuce (Lactuca sativa L. cv Evola) homozygous for the transgene. Apart from retardation of leaf senescence, mature, 60-d-old plants exhibited normal morphology with no significant differences in head diameter or fresh weight of leaves and roots. Induction of senescence by nitrogen starvation rapidly reduced total nitrogen, nitrate, and growth of transgenic and azygous (control) plants, but chlorophyll was retained in the lower (outer) leaves of transgenic plants. Harvested P(SAG12)-IPT heads also retained chlorophyll in their lower leaves. During later development (bolting and preflowering) of transgenic plants, the decrease in chlorophyll, total protein, and Rubisco content in leaves was abolished, resulting in a uniform distribution of these components throughout the plants. Homozygous P(SAG12)-IPT lettuce plants showed a slight delay in bolting (4-6 d), a severe delay in flowering (4-8 weeks), and premature senescence of their upper leaves. These changes correlated with significantly elevated concentrations of cytokinin and hexoses in the upper leaves of transgenic plants during later stages of development, implicating a relationship between cytokinin and hexose concentrations in senescence.
Plant physiology 11/2001; 127(2):505-16. · 6.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Microcolumn liquid chromatography (microLC) combined with electrospray tandem mass spectrometry is used for the determination of intact glycosylated cytokinins and the corresponding aglycons at picomole and sub-picomole levels in plant tissue. Routine analysis was done on C8-bonded silica using a methanol-water gradient. Data acquisition was performed by multiple reaction monitoring. Quantification was carried out by using isotopically labelled analogues and applying linear regression to the response factor versus concentration data. For routine analysis a calibration range from 0.5 to 10 pmole injected on-column was used. The limits of detection ranged from 50 to 100 fmole injected on-column. The microLC procedure was used to analyse plant tissue extracts from transgenic homozygote and hemizygote as well as wild-type Nicotiana tabacum species, and cauliflower samples. The data were compared with results obtained by conventional immunoassay and a satisfactory correlation was found. Validation data are presented.
Journal of Chromatography 10/2001; 929(1-2):31-42. · 4.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Using cDNA-AFLP RNA fingerprinting throughout potato tuber development, we have isolated a transcript-derived fragment (TDF511) with strong homology to plant steroid dehydrogenases. During in vitro tuberization, the abundance profile of the TDF shows close correlation to the process of tuber formation. However, when tuberization is inhibited by the addition of gibberellins (GAs) to the growth medium, the appearance of TDF511 in the fingerprint is delayed, then steadily increases in intensity during later stages of development. TDF511 was used to isolate the corresponding cDNA (CB12). The DNA and deduced amino-acid sequences of the cDNA show high homology to a fruit-ripening gene from tomato, a series of steroid dehydrogenases, and the maize Ts2 gene. A section of the cDNA was cloned in antisense orientation behind a 35S CaMV promoter and transformed into potato. Transgenic plants expressing the antisense gene showed significantly earlier emergence, an increase in height, and longer tuber shape. In vitro tuberization experiments reveal extended stolon lengths in comparison to the controls. The analysis of endogenous GA levels showed that the transgenic antisense plants have elevated levels of biologically active GAs and their respective precursors. We propose that this gene plays a role in the metabolism of plant-growth substances important for tuber life cycle and plant development.
The Plant Journal 04/2001; 25(6):595-604. · 6.16 Impact Factor
-
-
-
-
J. of Chrom. A, 929, p. 31-42.
-
-
Phytochemistry 49: 703-707.
-
Phytochemistry 42: 941-947.
-
Annals of Botany 83: 559-567.
-
Journal of Agricultural Food Chemistry 45: 4221-4226.
-
Plant, Cell and Environment (1999) 544, 22, p. 1-11.
-
Nota 122, AB-DLO, Wageningen, 38 pp. + bijlagen.
-
The Plant Journal 25 (2001).
-
-
[show abstract]
[hide abstract]
ABSTRACT: Cauliflower (Brassica oleracea var. botrytis) was transformed, using Agrobacterium tumefaciens, with an autoregulated isopentenyl transferase (ipt) gene under the control of a senescence-associated gene promoter, pSAG12, isolated from Arabidopsis thaliana. The effect of introducing this chimeric construct on cytokinin (CK) content, chlorophyll retention, and plant morphology and development were investigated. A range of CK and chlorophyll contents was found among the individual primary transformants. Progeny were studied from one of the primary transformed lines that did not have elevated cytokinin content and was phenotypically similar to the parent line but displayed delayed leaf senescence. The pSAG12:ipt gene was inherited in a Mendelian manner, and the effect of this gene on senescence-related parameters was observed in a number of the progeny. While the pSAG12:ipt progeny did exhibit delayed leaf senescence, it was accompanied by undesirable agronomic traits, including less synchronous curd initiation, smaller curd size, and greater susceptibility to fungal infection.
International Journal of Plant Sciences 169 (2008) 3.
-
[show abstract]
[hide abstract]
ABSTRACT: An ipt gene under control of the senescence-specific SAG12 promoter from Arabidopsis (PSAG12-IPT) significantly delayed developmental and postharvest leaf senescence in mature heads of transgenic lettuce (Lactuca sativa L. cv Evola) homozygous for the transgene. Apart from retardation of leaf senescence, mature, 60-d-old plants exhibited normal morphology with no significant differences in head diameter or fresh weight of leaves and roots. Induction of senescence by nitrogen starvation rapidly reduced total nitrogen, nitrate, and growth of transgenic and azygous (control) plants, but chlorophyll was retained in the lower (outer) leaves of transgenic plants. Harvested PSAG12-IPT heads also retained chlorophyll in their lower leaves. During later development (bolting and preflowering) of transgenic plants, the decrease in chlorophyll, total protein, and Rubisco content in leaves was abolished, resulting in a uniform distribution of these components throughout the plants. Homozygous PSAG12-IPT lettuce plants showed a slight delay in bolting (4-6 d), a severe delay in flowering (4-8 weeks), and premature senescence of their upper leaves. These changes correlated with significantly elevated concentrations of cytokinin and hexoses in the upper leaves of transgenic plants during later stages of development, implicating a relationship between cytokinin and hexose concentrations in senescence.
Plant Physiol. 127: 505-516.
-
[show abstract]
[hide abstract]
ABSTRACT: Using cDNA-AFLP RNA fingerprinting throughout potato tuber development, we have isolated a transcript-derived fragment (TDF511) with strong homology to plant steroid dehydrogenases. During in vitro tuberization, the abundance profile of the TDF shows close correlation to the process of tuber formation. However, when tuberization is inhibited by the addition of gibberellins (GAs) to the growth medium, the appearance of TDF511 in the fingerprint is delayed, then steadily increases in intensity during later stages of development. TDF511 was used to isolate the corresponding cDNA (CB12). The DNA and deduced amino-acid sequences of the cDNA show high homology to a fruit-ripening gene from tomato, a series of steroid dehydrogenases, and the maize Ts2 gene. A section of the cDNA was cloned in antisense orientation behind a 35S CaMV promoter and transformed into potato. Transgenic plants expressing the antisense gene showed significantly earlier emergence, an increase in height, and longer tuber shape. In vitro tuberization experiments reveal extended stolon lengths in comparison to the controls. The analysis of endogenous GA levels showed that the transgenic antisense plants have elevated levels of biologically active GAs and their respective precursors. We propose that this gene plays a role in the metabolism of plant-growth substances important for tuber life cycle and plant development
The Plant Journal 25 (2001) 6.
-
[show abstract]
[hide abstract]
ABSTRACT: Pythium aphanidermatum (Edson) Fitzp., causing root and crown rot in cucumber, was successfully managed by Lysobacter enzymogenes strain 3.1T8. Greenhouse experiments were performed with cucumber plants grown in rockwool blocks up to 5 weeks with a recirculated nutrient solution. Application of L. enzymogenes 3.1T8 in combination with chitosan (the deacetylated derivative of chitin) reduced the number of diseased plants by 50–100% in four independent experiments relative to the Pythium control. Application of chitosan or the bacterial inoculant alone was not effective. Washed bacterial cells plus chitosan inhibited Pythium-induced disease, but the supernatant without bacterial cells combined with chitosan was not effective. The most effective and convenient type of commercially available chitosan was selected. Chitosan disappeared from the hydroponic system within 24 h after application, which we attribute to enzyme expression of L. enzymogenes 3.1T8 induced by the exposure to chitosan. Plate counts of the nutrient solution on a general bacterial medium showed the dominance of the inoculated strain, and an increased bacterial population growing on chitin and chitosan as single carbon source. The population density of L. enzymogenes 3.1T8 on the cucumber roots was investigated with a strain specific real-time TaqMan PCR. Highest chitosan concentrations applied (0.1 and 0.03 g/plant) resulted in the highest numbers of L. enzymogenes 3.1T8 present on roots; i.e. 108–109 cells/g root. Substantially higher numbers of bacterial cells were observed by scanning electron microscopy after application of chitosan; no morphological or other qualitative differences were found. The results indicate that addition of chitosan enhanced the biocontrol efficacy of L. enzymogenes 3.1T8; either chitosan serves as C- and N-source for the antagonist, induces antagonistic gene expression, or both. Keywords: Biological control; Lysobacter enzymogenes; Chitosan; Synergistic effect; Quantitative PCR; Root colonization
Biological Control 48 (2009) 3.
