SuIfbydryl-Related and Phenylpropanoid-Synthesizing Enzymes in Arabidopsis thaliana Leaves after Treatments with Hydrogen Peroxide, Heavy Metals, and Glyphosate

SuIfbydryl-Related and Phenylpropanoid-Synthesizing Enzymes in Arabidopsis thaliana Leaves after Treatments with Hydrogen Peroxide, Heavy Metals, and Glyphosate

Three-week grown Arabidopsis thaliana leaves were wounded by cutting whole leaves with a razor blade into pieces (about 3 mm x 3 mm), submerged in various solutions, and incubated in a growth chamber for 24 h. We measured and compared activities of several enzymes such as phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), thioredoxin, thioredoxin reductase, thioltransferase, glutathione, reductase, and NADP+ -malate dehydrogenase. PAL activity was decreased in HgCI ₂ -, CdCJ ₂ -, and glyphosate-treated leaf slices, and could not be detected after treatment with CdCl ₂,. TAL activity was found to be maximal in the CdCl ₂-treated leaf slices. Activity of thioredoxin, a small protein known as a cofactor of ribonucleotide redutase and a regulator of photosynthesis, was significantly increased in the CdCl ₂ -treated leaf slices, while thioredoxin reductase activity was maximal in the HgCI ₂ -treated leaf slices. Thioltransferase and glutathione reductase activities were significantly decreased in the HgCl ₂ -treated leaf slices. NADP?? -malate dehydrogenase activity remained relatively constant after the chemical treatments. Our results strongly indicate that sulfhydryl-related and phenylpropanoid-synthesizing enzyme activities are affected by chemical treatments such as hydrogen peroxide, heavy metals, and glypbosate. Keywords: Arabidopsis thaliana, Chemical treatment. Phenylalanine ammonia-lyase (PAL), Thiohransferase