Spatial variation in H(2)O(2) response of Arabidopsis thaliana root epidermal Ca(2+) flux and plasma membrane Ca(2+) channels.
Hydrogen peroxide is an important regulatory agent in plants. This study demonstrates that exogenous H(2)O(2) application to Arabidopsis thaliana root epidermis results in dose-dependent transient increases in net Ca(2+) influx. The magnitude and duration of the transients were greater in the elongation zone than in the mature epidermis. In both regions, treatment with the cation channel blocker Gd(3+) prevented H(2)O(2)-induced net Ca(2+) influx, consistent with application of exogenous H(2)O(2) resulting in the activation of plasma membrane Gd(3+)-sensitive Ca(2+)-influx pathways. Application of 10 mm H(2)O(2) to the external plasma membrane face of elongation zone epidermal protoplasts resulted in the appearance of a hyperpolarization-activated Ca(2+)-permeable conductance. This conductance differed from that previously characterized as being responsive to extracellular hydroxyl radicals. In contrast, in mature epidermal protoplasts a plasma membrane hyperpolarization-activated Ca(2+)-permeable channel was activated only when H(2)O(2) was present at the intracellular membrane face. Channel open probability increased with intracellular [H(2)O(2)] and at hyperpolarized voltages. Unitary conductance decreased thus: Ba(2+) > Ca(2+) (14.5 pS) > Mg(2+) > Zn(2+) (20 mm external cation, 1 mm H(2)O(2)). Lanthanides and Zn(2+) (but not TEA(+)) suppressed the open probability without affecting current amplitude. The results suggest spatial heterogeneity and differential sensitivity of Ca(2+) channel activation by reactive oxygen species in the root that could underpin signalling.[1]References
- Spatial variation in H(2)O(2) response of Arabidopsis thaliana root epidermal Ca(2+) flux and plasma membrane Ca(2+) channels. Demidchik, V., Shabala, S.N., Davies, J.M. Plant J. (2007) [Pubmed]
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