Responses to drought, heat, and combined stress were compared in tobacco (Nicotiana tabacum L.) plants ectopically expressing the cytokinin oxidase/dehydrogenase CKX1 gene of Arabidopsis thaliana L. under the control of either the predominantly root-expressed WRKY6 promoter or the constitutive 35S promoter, and in the wild type. WRKY6:CKX1 plants exhibited high CKX activity in the roots under control conditions. Under stress, the activity of the WRKY6 promoter was down-regulated and the concomitantly reduced cytokinin degradation coincided with raised bioactive cytokinin levels during the early phase of the stress response, which might contribute to enhanced stress tolerance of this genotype. Constitutive expression of CKX1 resulted in an enlarged root system, a stunted, dwarf shoot phenotype, and a low basal level of expression of the dehydration marker gene ERD10B. The high drought tolerance of this genotype was associated with a relatively moderate drop in leaf water potential and a significant decrease in leaf osmotic potential. Basal expression of the proline biosynthetic gene P5CSA was raised. Both wild-type and WRKY6:CKX1 plants responded to heat stress by transient elevation of stomatal conductance, which correlated with an enhanced abscisic acid catabolism. 35S:CKX1 transgenic plants exhibited a small and delayed stomatal response. Nevertheless, they maintained a lower leaf temperature than the other genotypes. Heat shock applied to drought-stressed plants exaggerated the negative stress effects, probably due to the additional water loss caused by a transient stimulation of transpiration. The results indicate that modulation of cytokinin levels may positively affect plant responses to abiotic stress through a variety of physiological mechanisms.

Institute of Experimental Botany AS CR Rozvojová 263 16502 Prague 6 Czech Republic

Zobrazit více v PubMed

Aloni R, Langhans M, Aloni E, Dreieicher E, Ullrich CI. 2005. Root-synthesized cytokinin in Arabidopsis is distributed in the shoot by the transpiration stream. Journal of Experimental Botany 56, 1535–1544. PubMed

Boonman A, Prinsen E, Gilmer F, Schurr U, Peeters AJM, Voesenek LACJ, Pons TL. 2007. Cytokinin import rate as a signal for photosynthetic acclimation to canopy light gradients. Plant Physiology 143, 1841–1852. PubMed PMC

Boyer JS. 1995. Measuring the water status of plants and soils. New York: Academic Press.

Dobra J, Vankova R, Havlova M, Burman AJ, Libus J, Storchova H. 2011. Tobacco leaves and roots differ in the expression of proline metabolism-related genes in the course of drought stress and subsequent recovery. Journal of Plant Physiology 168, 1588–1597. PubMed

Gajdosova S, Spichal L, Kaminek M, et al. 2011. Distribution, biological activities, metabolism, and the conceivable function of cis-zeatin-type cytokinins in plants. Journal of Experimental Botany 62, 2827–2840. PubMed

Haisel D, Vankova R, Synkova H, Pospisilova J. 2008. The impact of trans-zeatin O-glucosyltransferase gene over-expression in tobacco on pigment content and gas exchange. Biologia Plantarum 52, 49–58.

Havlova M, Dobrev PI, Motyka V, Storchova H, Libus J, Dobra J, Malbeck J, Gaudinova A, Vankova R. 2008. The role of cytokinins in responses to water deficit in tobacco plants over-expressing trans-zeatin O-glucosyltransferase gene under 35S or SAG12 promoters. Plant, Cell and Environment 31, 341–353. PubMed

Heyl A, Ramireddy E, Brenner WG, Riefler M, Allemeersch J, Schmülling T. 2008. The transcriptional silencer ARR1-SRDX suppresses pleiotropic cytokinin activities in Arabidopsis. Plant Physiology 147, 1380–1395. PubMed PMC

Miyawaki K, Tarkowski P, Matsumoto-Kitano M, Kato T, Sato S, Tarkowska D, Tabata S, Sandberg G, Kakimoto T. 2006. Roles of Arabidopsis ATP/ADP isopentenyltransferases and tRNA isopentenyltransferases in cytokinin biosynthesis. Proceedings of the National Academy of Sciences, USA 103, 16598–16603. PubMed PMC

Motyka V, Vankova R, Capkova V, Petrasek J, Kaminek M, Schmülling T. 2003. Cytokinin-induced upregulation of cytokinin oxidase activity in tobacco includes changes in enzyme glycosylation and secretion. Physiologia Plantarum 117, 11–21.

Nishiyama R, Watanabe Y, Fujita Y, et al. 2011. Analysis of cytokinin mutants and regulation of cytokinin metabolic genes reveals important regulatory roles of cytokinins in drought, salt and abscisic acid responses, and abscisic acid biosynthesis. The Plant Cell 23, 2169–2183. PubMed PMC

Novak O, Hauserova E, Amakorova P, Dolezal K, Strnad M. 2008. Cytokinin profiling in plant tissues using ultra-performance liquid chromatography–electrospray tandem mass spectrometry. Phytochemistry 69, 2214–2224. PubMed

Novak O, Tarkowski P, Tarkowska D, Dolezal K, Lenobel R, Strnad M. 2003. Quantitative analysis of cytokinins in plants by liquid chromatography/single-quadrupole mass spectrometry. Analytica Chimica Acta 480, 207–218.

Orsini F, Alnayef M, Bona S, Maggio A, Gianquinto G. 2012. Low stomatal density and reduced transpiration facilitate strawberry adaptation to salinity. Environmental and Experimental Botany 81, 1–10.

Peleg Z, Reguera M, Tumimbang E, Walia H, Blumwald E. 2011. Cytokinin-mediated source/sink modifications improve drought tolerance and increase grain yield in rice under water-stress. Plant Biotechnology Journal 9, 747– –758. PubMed

Riefler M, Novak O, Strnad M, Schmülling T. 2006. Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism. The Plant Cell 18, 40–54. PubMed PMC

Rivero RM, Kojima M, Gepstein A, Sakakibara H, Mittler R, Gepstein S, Blumwald E. 2007. Delayed leaf senescence induces extreme drought tolerance in a flowering plant. Proceedings of the National Academy of Sciences, USA 104, 19631–19636. PubMed PMC

Rivero RM, Shulaev V, Blumwald E. 2009. Cytokinin-dependent photorespiration and the protection of photosynthesis during water deficit. Plant Physiology 150, 1530–1540. PubMed PMC

Shkolnik-Inbar D, Bar-Zvi D. 2010. ABI4 mediates abscisic acid and cytokinin inhibition of lateral root formation by reducing polar auxin transport in Arabidopsis. The Plant Cell 22, 3560–3573. PubMed PMC

Tuberosa R, Sanguineti MC, Landi P, Giuliani M, Salvi S, Conti S. 2002. Identification of QTLs for root characteristics in maize grown in hydroponics and analysis of their overlap with QTLs for grain yield in the field at two water regimes. Plant Molecular Biology 48, 697–712. PubMed

Tureckova V, Novak O, Strnad M. 2009. Profiling ABA metabolites in Nicotiana tabacum L. leaves by ultra-performance liquid chromatography–electrospray tandem mass spectrometry. Talanta 80, 390–399. PubMed

Vysotskaya LB, Veselov SYu, Kudoyarova GR. 2010. Effect on shoot water relations, and cytokinin and abscisic acid levels of inducing expression of a gene coding for isopentenyltransferase in roots of transgenic tobacco plants. Journal of Exerimental Botany 61, 3709–3717. PubMed

Wahid A, Gelani S, Ashraf M, Foolad MR. 2007. Heat tolerance in plants: an overview. Enviromental and Experimental Botany 61, 199–223.

Werner T, Motyka V, Laucou V, Smets R, Van Onckelen H, Schmülling T. 2003. Cytokinin-deficient transgenic Arabidopsis plants show multiple developmental alterations indicating opposite functions of cytokinins in the regulation of shoot and root meristem activity. The Plant Cell 15, 2532–2550. PubMed PMC

Werner T, Motyka V, Strnad M, Schmülling T. 2001. Regulation of plant growth by cytokinin. Proceedings of the National Academy of Sciences, USA 98, 10487–10492. PubMed PMC

Werner T, Nehnevajova E, Kollmer I, Novak O, Strnad M, Kramer U, Schmülling T. 2010. Root-specific reduction of cytokinin causes enhanced root growth, drought tolerance, and leaf mineral enrichment in Arabidopsis and tobacco. The Plant Cell 22, 3905–3920. PubMed PMC

Impairment of root auxin-cytokinins homeostasis induces collapse of incompatible melon grafts during fruit ripening

Phytohormone profiles in non-transformed and AtCKX transgenic centaury (Centaurium erythraea Rafn) shoots and roots in response to salinity stress in vitro

Crosstalk between Light- and Temperature-Mediated Processes under Cold and Heat Stress Conditions in Plants

The Resistance of Oilseed Rape Microspore-Derived Embryos to Osmotic Stress Is Associated With the Accumulation of Energy Metabolism Proteins, Redox Homeostasis, Higher Abscisic Acid, and Cytokinin Contents

Signal Integration in Plant Abiotic Stress Responses via Multistep Phosphorelay Signaling

Heat Stress Targeting Individual Organs Reveals the Central Role of Roots and Crowns in Rice Stress Responses

Barley Root Proteome and Metabolome in Response to Cytokinin and Abiotic Stimuli

Applications of Cytokinins in Horticultural Fruit Crops: Trends and Future Prospects

Response of cytokinins and nitrogen metabolism in the fronds of Pteris sp. under arsenic stress

Heat Acclimation and Inhibition of Cytokinin Degradation Positively Affect Heat Stress Tolerance of Arabidopsis

Root enhancement in cytokinin-deficient oilseed rape causes leaf mineral enrichment, increases the chlorophyll concentration under nutrient limitation and enhances the phytoremediation capacity

Modification of Barley Plant Productivity Through Regulation of Cytokinin Content by Reverse-Genetics Approaches

Root exudate metabolomes change under drought and show limited capacity for recovery

Cytokinin at the Crossroads of Abiotic Stress Signalling Pathways

Salt and oxidative stresses uniquely regulate tomato cytokinin levels and transcriptomic response

Cytokinins: Their Impact on Molecular and Growth Responses to Drought Stress and Recovery in Arabidopsis

Plants under Stress: Involvement of Auxin and Cytokinin

Depletion of carbohydrate reserves limits nitrate uptake during early regrowth in Lolium perenne L

Stimulation of ipt overexpression as a tool to elucidate the role of cytokinins in high temperature responses of Arabidopsis thaliana

The role of cis-zeatin-type cytokinins in plant growth regulation and mediating responses to environmental interactions