Lara, Maria Encarnacioén Balibrea and Garcia, Maria-Cruz Gonzalez and Fatima, Tahira and Ehness, Rainer and Lee, Taek Kyun and Proels, Reinhard and Tanner, Widmar and Roitsch, Thomas (2004) Extracellular invertase is an essential component of cytokinin-mediated delay of senescence. PLANT CELL, 16 (5). pp. 1276-1287. ISSN 1040-4651, 1532-298X
Full text not available from this repository. (Request a copy)Abstract
Leaf senescence is the final stage of leaf development in which the nutrients invested in the leaf are remobilized to other parts of the plant. Whereas senescence is accompanied by a decline in leaf cytokinin content, exogenous application of cytokinins or an increase of the endogenous concentration delays senescence and causes nutrient mobilization. The finding that extracellular invertase and hexose transporters, as the functionally linked enzymes of an apolasmic phloem unloading pathway, are coinduced by cytokinins suggested that delay of senescence is mediated via an effect on source-sink relations. This hypothesis was further substantiated in this study by the finding that delay of senescence in transgenic tobacco (Nicotiana tabacum) plants with autoregulated cytokinin production correlates with an elevated extracellular invertase activity. The finding that the expression of an extracellular invertase under control of the senescence-induced SAG12 promoter results in a delay of senescence demonstrates that effect of cytokinins may be substituted by these metabolic enzymes. The observation that an increase in extracellular invertase is sufficient to delay leaf senescence was further verified by a complementing functional approach. Localized induction of an extracellular invertase under control of a chemically inducible promoter resulted in ectopic delay of senescence, resembling the naturally occurring green islands in autumn leaves. To establish a causal relationship between cytokinins and extracellular invertase for the delay of senescence, transgenic plants were generated that allowed inhibition of extracellular invertase in the presence of cytokinins. For this purpose, an invertase inhibitor was expressed under control of a cytokinin-inducible promoter. It has been shown that senescence is not any more delayed by cytokinin when the expression of the invertase inhibitor is elevated. 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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CELL-WALL INVERTASE; SIGNAL-TRANSDUCTION PATHWAYS; LEAF SENESCENCE; APOPLASTIC INVERTASE; CHENOPODIUM-RUBRUM; ARABIDOPSIS-THALIANA; CARNATION PETALS; SINK METABOLISM; GENE-EXPRESSION; TOBACCO PLANTS; |
| Subjects: | 500 Science > 580 Botanical sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Pflanzenwissenschaften > Lehrstuhl für Zellbiologie und Pflanzenphysiologie (Prof. Dr. Klaus Grasser) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 21 Jul 2021 06:29 |
| Last Modified: | 21 Jul 2021 06:29 |
| URI: | https://pred.uni-regensburg.de/id/eprint/37724 |
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