Cd significantly inhibited the growth of both rice cultivars. The Tainung 67 cultivar is more tolerant to Cd than Taichung 1 cultivar after 48 h incubation in CdCl2 solution. The Cd tolerant cultivar¡XTainung 67¡¦s PODs in roots might synthesize more lignin in Cd-treatments. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POD activity in Cd-treated tissues. PODs here might also remove excess H2O2, thus serving detoxifying role and synthesizing more lignin for protection. In Taichung 1 cultivar, the accumulation of H2O2 in Cd-treated tissues could be due to the less amount of POD enhancement induced by Cd. In response to Cd treatment, the Taichung 1 cultivar also synthesizes little lignin, and therefore is Cd-sensitive.

Maintenance of a stable arterial blood pressure is a complex physiological phenomenon. In addition to dysfunction of the blood vessels, alterations in homeostasis of circulating signals and humoral factors also contribute significantly to the development of hypertension. Recent evidence indicates that accumulation of the byproducts of cellular respiration, including superoxide anion (O2-) and/or hydrogen peroxide (H2O2), are contributing factors in pathophysiology of hypertension. With respect to the central nervous system, neurons in the rostral ventrolateral medulla (RVLM) play a pivotal role in neural regulation of blood pressure. RVLM neurons not only provide a tonic excitation to maintain the sympathetic vasomotor activity of the blood vessels, they also participate in baroreceptor reflex control of blood pressure. The notion that production of O2- and/or H2O2 in the RVLM participates in central control of blood pressure has recently gained major recognition in the area of hypertension study. Nonetheless, detailed insights into the mechanisms underlying O2- and/or H2O2 promoted hypertension remain to be elucidated. The hypothesis that forms the basis of this study is that enhanced level of O2- and/or H2O2 in the RVLM may be important factors for the manifestation of hypertension in the spontaneously hypertensive rats (SHR), an animal model of human essential hypertension. In comparison to normotensive Wistar-Kyoto (WKY) rats, basal level of O2- in the RVLM region of adult male SHR rats was significantly higher, along with a reduction in the expression of superoxide dismutase 1 (SOD1), SOD2 or catalase. SOD and catalase are enzymes that metabolize cellular O2- or H2O2 respectively. Pharmacologically, microinjection bilaterally into the RVLM of SOD mimetic, Tempol (50 nmol) or a pan SOD/calatase mimetic, FeTMPyP (100 nmol), significantly decreased mean systemic arterial pressure (MSAP) or heart rate (HR) in both SHR and WKY rats. The maximal hypotensive effect produced by Tempol or FeTMPyP was significantly greater in SHR than WKY rats. We also found that in SHR, but not WKY rats, the hypotensive and bradycardiac responses after microinjection bilaterally into the RVLM of FeTMPyP was significantly greater than that by Tempol. In addition, infection of RVLM neurons with adenoviral vector encoding SOD1 (Ad-SOD1), SOD2 (Ad-SOD2) or catalase (Ad-Catalase) gene (5x108 pfu) into the bilateral RVLM resulted in a long-term hypotensive effect in SHR but not WKY rats. The temporal profile of Ad-catalase-promoted hypotension was again longer than that promoted by Ad-SOD1 or Ad-SOD2 alone. At the molecular level, gene transfer of SOD1, SOD2 or catalase into the RVLM region of SHR or WKY rats specifically increased the expression of individual protein, resulting in a reduction in O2- level. Together these results suggest that accumulation of O2- and/or H2O2 in the RVLM is involved in the neural mechanism of hypertension in SHR.

The adverse effect of Cu on growth is apparent from the reduction in root length of the Cu-treated Arabidopsis roots. Arabidopsis seems to be more resistant to Cu in comparison with that of soybean in terms of root growth. The increase of the levels of H2O2 was observed in Cu-treated Arabidopsis roots. The lignin biosynthesis related enzymes, PODs and laccases were enhanced during the Cu treatments. The lignin contents slightly increased in Cu-treated Arabidopsis roots. To our surprise, the Arabidopsis can be tolerant to high concentration of Cu (200 µM), because only part of high levels of H2O2 accumulated in Cu-treated tissues are used by PODs to synthesize the lignin.

Copper-treated rice seeding (Oryza sativa cv. Tainung 67 and Taichung native 1) showed significant inhibition in rice root growth, and an enhancement in POD activity. POD within Tainung 67 rice roots might synthesize more lignin in Cu-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POD activity in Cu-treated tissues. The increase in POD activity induced by Cu might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 rice cultivar, high amounts of H2O2 accumulated in Cu-treated tissues could be due to the less amounts of POD induced by Cu. In response to Cu treatment, the Taichung native 1 cultivar also synthesizes a little lignin, and is more Cu-sensitive. Therefore, The Tainung 67 cultivar is more tolerant to Cu than Taichung native 1.

Cadmium-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed inhibition in the growth of rice roots or leaves, and an enhancement in POX activity. In Tainung 67 cultivar, Cd treatment may have influence over cis-regulatory elements in POX promoter region and enhanced transcription of POX or enhance glycosylation of POX. The increase in POX activity induced by Cd might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung Native 1 cultivar, high amounts of H2O2 accumulated in Cd-treated tissues could be due to the less amounts of POX induced by Cd. In response to Cd treatment, the Taichung Native 1 cultivar also synthesizes a little lignin, and is more Cd-sensitive. Therefore, the Tainung 67 cultivar is more tolerant to Cd than Taichung Native 1.

The adverse effect of Cd on growth is apparent from the reduction in root length of the Cd-treated Arabidopsis thaliana roots. The increase of the levels of H2O2 was observed in Cd-treated A. thaliana roots. The lignin biosynthesis related enzymes, POXs and laccases were enhanced during the Cd treatments. The lignin contents slightly increased in Cd-treated A. thaliana roots¡]48 h¡^. The A. thaliana can be tolerant to high concentration of Cd (500 µM), and only part of high levels of H2O2 accumulated in Cd-treated tissues are used by POXs to synthesize the lignin.

The adverse effect of Zn on growth is apparent from the reduction in root length of the Zn-treated Arabidopsis roots. The levels of H2O2 were increased rapidly in Zn-treated Arabidopsis roots. The lignin biosynthesis realated enzymes, peroxidases and laccases were enhanced during the Zn treatments. The lignin contents increased in Zn-treated Arabidopsis roots. Arabidopsis can be tolerant to high concentration of Zn (4 mM), because part of high levels of H2O2 accumulated in Zn-treated tissues are utilized by peroxidases to synthesize the lignin.

The E. coli ArsA is involved in arsenic detoxification but the role of yArsA (ArsA homologue of Saccharomyces cerevisiae, encoded by YDL100C ORF) in yeast is still undefined. Disruption of YDL100C ORF is not lethal. To study the role of yArsA in oxidative tolerance, wild type and knock out strain were grown in presence or absence of 1 mM H2O2 and assayed the expression of anti-oxidation machanisms . The results show that molecular oxidation is higher and catalase activity is lower in KO compared with WT. It suggests that increased ROS and decreased catalase activity are the cause of cell death. Further analysis of the expression of ROS defense mechanisms by RT-PCR show that there is no significant difference in TRR1, GSH1, and SOD1 expression in WT and KO grown in presence of 1 mM H2O2 but the CTT1, TPS1, NTH1 expression in KO are less than WT grown under oxidative stress. GSH contents is consistent with the result of RT-PCR, and trehalose contents is higher in KO strain under oxidative stress. Loss of catalase activity and decreased efficiency of degrading trehalose suggest that the deficiency in activation of general stress response in KO when grown in the presence of H2O2. Therefore, yArsA would be involved in expressing the general stress response in oxidative tolerance.

Aluminum-treated rice seeding (Oryza sativa L. cv. Taichung Native 1 and O. sativa L. cv. Tainung 67) showed significant inhibition in rice root growth, and an enhancement of POX activity. In Tainung 67 cultivar rice synthesizes more lignin in Al-treated tissue. Meanwhile, the decrease of H2O2 levels is accompanied with the enhancement of POX activity in Al-treated tissue. The increase in POX activity induced by Al might remove excess hydrogen peroxide serving a detoxifying role and synthesizing more lignin for protection. In Taichung native 1 cultivar, high amounts of H2O2 accumulated in Al-treated tissues could be due to the less amounts of POX induced by Al. In response to Al treatment, the Taichung native 1 cultivar synthesizes less lignin in comparison with that of Tainung 67, and is more Al-less tolerant. Therefore, the Tainung 67 cultivar is more tolerant to Al than Taichung native 1.

No description available.