Nitric Oxide Is Involved in Cadmium-Induced Programmed Cell Death in Arabidopsis Suspension Cultures1[C][W]

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FONTE

American Society of Plant Biologists

RESUMO

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 NG-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.

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