Inhibition of Leaf Senescence by Autoregulated Production of Cytokinin

  title={Inhibition of Leaf Senescence by Autoregulated Production of Cytokinin},
  author={Susheng Gan and Richard M. Amasino},
  pages={1986 - 1988}
Controlling expression of IPT, a gene encoding isopentenyl transferase (the enzyme that catalyzes the rate-limiting step in cytokinin biosynthesis), with a senescence-specific promoter results in the suppression of leaf senescence. Transgenic tobacco plants expressing this chimeric gene do not exhibit the developmental abnormalities usually associated with IPT expression because the system is autoregulatory. Because sufficient cytokinin is produced to retard senescence, the activity of the… 
Cytokinins in plant senescence: From spray and pray to clone and play
A recently developed autoregulatory senescence‐inhibition system targets cytokinin production quantitatively, spatially and temporally, and results in transgenic plants that exhibit significantly delayedsenescence without abnormalities.
Molecular markers of delayed senescence in transgenic tobacco with enhanced cytokinin level
The capacity of elevated hormone level in the transgenic tobacco to reduce chlorophyll, soluble proteins and Rubisco degradation in plants exposed to nine days of light deprivation and possible correlation between the enhanced cytokinin synthesis and antioxidant properties of PSAG12-IPT plants analyzing three isoforms of superoxide dismutase is investigated.
Extracellular Invertase Is an Essential Component of Cytokinin-Mediated Delay of Senescence
This finding demonstrates that extracellular invertase is required for the delay of senescence by cytokinins and that it is a key element of the underlying molecular mechanism.
Delay of leaf senescence in Medicago sativa transformed with the ipt gene controlled by the senescence-specific promoter SAG12
In vitro and in vivo analyses showed that SAG12-IPT plants exhibited a stay-green phenotype that has the potential to greatly improve the quantity and quality of alfalfa forage.
Regulation of plant growth by cytokinin
It is suggested that cytokinins are an important regulatory factor of plant meristem activity and morphogenesis, with opposing roles in shoots and roots.
Senescence and Genetic Engineering
Identification of antagonistic or promoting roles of cytokinin or ethylene, respectively, in plant senescence provides a framework to overcome problems associated with Senescence in agriculture.
Effect of cytokinins on oxidative stress in tobacco plants under nitrogen deficiency
The results suggest that the increased cytokinin synthesis in the transgenic plants is an effective mechanism to improve N-use efficiency.
Relationship between hexokinase and cytokinin in the regulation of leaf senescence and seed germination.
Investigation of the relationship between hexokinase and cytokinin in the regulation of leaf senescence in tomato plants suggests that intracellular sugar sensing via AtHXK1 is dominant over extracellular Sugar sensing with regard to leafSenescence.
Senescence-induced ectopic expression of the A. tumefaciens ipt gene in wheat delays leaf senescence, increases cytokinin content, nitrate influx, and nitrate reductase activity, but does not affect grain yield.
The results suggest that the delay of leaf senescence in wheat also delays the translocation of metabolites from leaves to developing grains, as indicated by higher accumulation of ((15)N-labelled) N in spikes of control compared with transgenic plants prior to anthesis.
Identification of a promoter region responsible for the senescence-specific expression of SAG12
It is shown that cytokinin, auxin, and sugars can repress developmental senescence at the molecular level, and studies using promoter deletions and recombination of promoter fragments indicate that a highly conserved region of the SAG12 promoter is responsible for Senescence-specific regulation, while at least two other regions are important for full promoter activity.


Delayed Leaf Senescence in Tobacco Plants Transformed with tmr, a Gene for Cytokinin Production in Agrobacterium.
It is demonstrated that plant morphology and leaf senescence can be manipulated by changing the endogenous level of cytokinin, which encodes the enzyme isopentenyl transferase, which catalyzes the initial step in cytokinIn biosynthesis.
Altered morphology in transgenic tobacco plants that overproduce cytokinins in specific tissues and organs.
The tissue- and organ-specific overproduction of cytokinins produced a number of morphological and physiological changes, including stunting, loss of apical dominance, reduction in root initiation and growth, and adventitious shoot formation from unwounded leaf veins and petioles, altered nutrient distribution, and abnormal tissue development in stems.
Molecular analysis of natural leaf senescence in Arabidopsis thaliana
It is shown that major changes in gene expression occur in Arabidopsis leaves during the process of senescence, and that these changes are accompanied by a specific pattern of decline of total RNA and proteins.
Promoter tagging with a promoterless ipt gene leads to cytokinin-induced phenotypic variability in transgenic tobacco plants:implications of gene dosage effects.
The results show that stably inherited developmental alterations due to a general or localized cytokinin overproduction can be obtained by the promoter-tagging approach.
Fruit‐specific expression of the A. tumefaciens isopentenyl transferase gene in tomato: effects on fruit ripening and defense‐related gene expression in leaves
Analysis of tomato plants transformed with a chimeric gene consisting of the promoter region of a fruit specifically expressed tomato gene linked to the ipt gene coding sequences from the Ti plasmid of Agrobacterium tumefaciens found the pattern of expression was found to be consistent with the expression of the endogenous fruit-specific gene and consequently, plants expressing the Chimeric gene were phenotypically normal until fruit maturation and ripening.
Prevention of Monocarpic Senescence in Soybeans with Auxin and Cytokinin: An Antidote for Self-Destruction
Foliar applications of α-naphthaleneacetic acid, together with 6-benzyladenine, prevent the seed-induced degeneration (monocarpic senescence) in soybeans and prevents the loss of starch and nitrogen that occurs during senescences of these leaves.
Cytokinin biochemistry in relation to leaf senescence. VII. Endogenous cytokinin levels and exogenous applications of cytokinins in relation to sequential leaf senescence of tobacco
When supplied exogenously, the principal cytokinin bases found to occur in tobacco leaves (zeatin and dihydrozeatin) were markedly more effective than auxins and gibberellic acid in retarding senescence.
A simple and general method for transferring genes into plants.
This method for producing transformed plants combines gene transfer, plant regeneration, and effective selection for transformants into a single process and should be applicable to plant species that can be infected by Agrobacterium and regenerated from leaf explants.