title: Species-specific enzymatic tolerance of sulfide toxicity in plant roots.
abstract: Toxic effects of sulfide come from a poisoning of a number of enzymes, especially cytochrome c oxidase, which catalyzes the terminal step in mitochondrial aerobic respiration. Despite this, some estuarine plants live in sulfide-rich sediments. We hypothesized estuarine and flooding-tolerant species might be more tolerant of sulfide compared to upland species, and this was tested by measures of root cytochrome c oxidase and alcohol dehydrogenase activities in extracts exposed to sulfide. Enzyme activities were measured in 0, 5, 10, 15, and 20 μM sodium sulfide, and compared among 17 species of plants. Activities of alcohol dehydrogenase and cytochrome c oxidase were both reduced by increasing sulfide concentration, but cytochrome c oxidase was more sensitive to sulfide compared to alcohol dehydrogenase. Activities of cytochrome c oxidase were reduced to near zero at 5-10 μM sulfide whereas alcohol dehydrogenase activities were only reduced by about 50% at 10 μM sulfide. All species were sensitive to increasing sulfide, but to different degrees. Cytochrome c oxidase in flooding-sensitive species was decreased to near zero activity at 5 μM sulfide, whereas activities in some flooding-tolerant species were still detectable until 15 μM sulfide. Cytochrome c oxidase activities in some estuarine species were low even in the absence of sulfide, perhaps an adaptation to avoid sulfide vulnerability in their native, sulfide-rich habitat. This illustrates the potent metabolic effects of sulfide, and this is the first demonstration of varying sensitivities of cytochrome c oxidase to sulfide across organisms, making these data of novel importance.
authors: Department of Biological Sciences, Fort Hays State University, Hays, KS, 67601-4099, USA.
authors: Nicole M
authors: NM
authors: Martin
authors: Department of Biological Sciences, Fort Hays State University, Hays, KS, 67601-4099, USA. Electronic address: brmaricle@fhsu.edu.
authors: Brian R
authors: BR
authors: Maricle
mesh_terms: D000222:Adaptation, Physiological; D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D017753:Ecosystem; D003576:Electron Transport Complex IV / Q000378:metabolism*; D063366:Estuaries; D055868:Floods; D008928:Mitochondria / Q000187:drug effects; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects* / Q000201:enzymology; D010944:Plants / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D013045:Species Specificity; D013312:Stress, Physiological; D013440:Sulfides / Q000009:adverse effects* / Q000378:metabolism; D014867:Water
chemical_list: D010940:Plant Proteins; D013440:Sulfides; D014867:Water; D000426:Alcohol Dehydrogenase; D003576:Electron Transport Complex IV; C033479:sodium sulfide
keywords: Alcohol dehydrogenase; Cytochrome c oxidase; Estuarine plants; Flooding-sensitive plants; Flooding-tolerant plants; Respiration; Sulfide
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