Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 194 (2011)
(How) do polyamines mediate stress tolerance in barley?
Nancy Nowak, Heidrun Beschow, Liane Freitag and Edgar Peiter
The Plant Nutrition Laboratory, Martin-Luther-Universität Halle-Wittenberg, Halle. E-Mail: nancy.nowak
@landw.uni-halle.de
Introduction
Worldwide, drought is the main yield-limiting factor in crop production. Drought
resistance is therefore a major goal for crop research. Polyamines play a central role
in abiotic stress tolerance of plants in general and drought tolerance in particular
(Alcazar et. al 2006). Common polyamines in plants are putrescine, spermidine and
spermine. Recent studies show that spermine seems to play a specific role in stress
tolerance. The aim of this project is to investigate the role of spermine and its
structural isomer thermospermine in drought stress tolerance of barley. We
hypothesise that polyamines modulate abiotic stress-related Ca 2+ signals, which in
turn would affect stress tolerance mechanisms.
Materials and Methods
Barley (Hordeum vulgare L.) plants were grown in a growth chamber at 22°C, 65%
relative humidity and a photoperiod with 16h light and 8h darkness. Genes encoding
proteins possibly mediating of the synthesis of spermine and thermospermine in
barley were identified and full-length cDNA sequences were obtained according to
standard methods. For overexpression and RNAi-induced silencing of those genes
we cloned cDNAs into the binary vector pLH6000. The vector was transformed into
Agrobacterium tumefaciens by electroporation. Genetic transformation of barley was
performed as described by Tingay et al. 1997. For cell culture experiments we
established a new suspension culture from callus. Callus and cell cultures were
grown in modified Murashige and Skoog medium. Pharmacological experiments on
tissue cultures and intact plants were carried out on hydroponically-grown plants.
Results and Discussion
For the reverse genetic analysis of spermine synthases in barley, an immature
embryo-based transformation protocol has sucessfully been established in the
laboratory, with transformation efficiencies of around 30%. Initial pharmacological
experiments on whole plants have yielded the unexpected result that application of
spermine to the root medium affected the plant’s osmotic stress tolerance in a
negative way. Current examinations indicate that this effect may have been caused
by bacterial degradation products. Also, in first suspension culture experiments the
application of the polyamine spermine caused a diminished cell growth. For a better
understanding of polyamine action in barley the regulation of stress-related [Ca 2+ ]cyt
signalling by polyamines is currently being analysed.
References
Alcazar, R., F. Marco, J.C. Cuevas, M. Patron, A. Ferrando, P. Carrasco, A.F. Tiburcio, T. Altabella
2006: Involvement of polyamines in plant response to abiotic stress. Biotechnol. Lett 28:1867-1876.
Tingay, S., D. McElroy, R. Kalla, S. Fieg, M. Wang, S. Thornton, R. Brettell 1997: Agrobacterium
tumefaciens-mediated barley transformation. Plant J. 11:1369-1376.