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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Nitric Oxide Is Involved in Cadmium-Induced Programmed Cell Death in Arabidopsis Suspension Cultures^1,[C],[W]

Dipartimento di Biologia, Università degli Studi di Padova, I–35131 Padova, Italy (R.D.M., C.R., A.C., M.Z., F.L.S.); Dipartimento di Biologia Evolutiva e Funzionale, Università degli Studi di Parma, I–43100 Parma, Italy (E.V., L.S.d.T.); Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, I–43100 Parma, Italy (L.E., M.C.); and Dipartimento di Scienze Chimiche, Università degli Studi di Padova, I–35131 Padova, Italy (M.D.V.)

Exposure to cadmium (Cd²⁺) can result in cell death, but the molecular mechanisms of Cd²⁺ cytotoxicity in plants are not fully understood. Here, we show that Arabidopsis (Arabidopsis thaliana) cell suspension cultures underwent a process of programmed cell death when exposed to 100 and 150 µM CdCl₂ and that this process resembled an accelerated senescence, as suggested by the expression of the marker senescence-associated gene12 (SAG12). CdCl₂ treatment was accompanied by a rapid increase in nitric oxide (NO) and phytochelatin synthesis, which continued to be high as long as cells remained viable. Hydrogen peroxide production was a later event and preceded the rise of cell death by about 24 h. Inhibition of NO synthesis by N^G-monomethyl-arginine monoacetate resulted in partial prevention of hydrogen peroxide increase, SAG12 expression, and mortality, indicating that NO is actually required for Cd²⁺-induced cell death. NO also modulated the extent of phytochelatin content, and possibly their function, by S-nitrosylation. These results shed light on the signaling events controlling Cd²⁺ cytotoxicity in plants.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Roberto De Michele (demicheler{at}virgilio.it).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.133397

^* Corresponding author; e-mail demicheler{at}virgilio.it.

Received November 28, 2008; accepted March 1, 2009; published March 4, 2009.

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Plant Physiol. 2009 150: 1-2. [Full Text]