Macková H., Hronková M., Dobrá J., Turečková V., Novák O., Lubovská Z., Motyka V., Haisel D., Hájek T., Prášil I.T., Gaudinová A., Štorchová H., Ge E., Werner T., Schmülling T., Vanková R.
JOURNAL OF EXPERIMENTAL BOTANY
64:
2805-2815,
2013
Keywords:
Abscisic acid, cytokinin, cytokinin oxidase/dehydrogenase, drought stress, heat stress, tobacco
Abstract:
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.
Fulltext: contact IEB authors
IEB authors: Alena Gaudinová,
Eva Ge,
Daniel Haisel,
Václav Motyka,
Ondřej Novák,
Helena Štorchová,
Radomíra Vanková
Čeština
English