Effect of Ca²⁺ on Programmed Death of guard and epidermal cells of pea leaves

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D. B. Kiselevsky¹, Yu. E. Kuznetsova¹, L. A. Vasil’ev¹, N. V. Lobysheva², R. A. Zinovkin^1,2, A. V. Nesov¹, A. A. Shestak¹, and V. D. Samuilov^1*

¹Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3807; E-mail: vdsamuilov@mail.ru

²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3181

^* To whom correspondence should be addressed.

Received May 8, 2009; Revision received June 9, 2009

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The effect of Ca²⁺ on programmed death of guard cells (GC) and epidermal cells (EC) determined from destruction of the cell nucleus was investigated in epidermis of pea leaves. Ca²⁺ at concentrations of 1-100 µM increased and at a concentration of 1 mM prevented the CN^–-induced destruction of the nucleus in GC, disrupting the permeability barrier of GC plasma membrane for propidium iodide (PI). Ca²⁺ at concentrations of 0.1-1 mM enhanced drastically the number of EC nuclei stained by PI in epidermis treated with chitosan, an inducer of programmed cell death. The internucleosomal DNA fragmentation caused by CN^– was suppressed by 2 mM Ca²⁺ on 6 h incubation, but fragmentation was stimulated on more prolonged treatment (16 h). Presumably, the disruption of the permeability barrier of plasma membrane for PI is not a sign of necrosis in plant cells. Quinacrine and diphenylene iodonium at 50 µM concentration prevented GC death induced by CN^– or CN^– + 0.1 mM Ca²⁺ but had no influence on respiration and photosynthetic O₂ evolution in pea leaf slices. The generation of reactive oxygen species determined from 2′,7′-dichlorofluorescein fluorescence was promoted by Ca²⁺ in epidermal peels from pea leaves.

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KEY WORDS: reactive oxygen species, calcium, programmed cell death, necrosis, guard cells, epidermal cells, leaves, pea

DOI: 10.1134/S0006297910050111

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