The use of 3‐amino‐1,2,4‐triazole to investigate the short‐term effects of oxygen toxicity on carbon assimilation by Pisum sativum seedlings

Abstract

To study the in vivo short-term effect of hydrogen peroxide on plant metabolism, 2 mol m~^ 3-amino-1,2,4-triazole, a catalase inhibitor, was applied through the transpiration stream to Pisum sativum seedlings, and gas exchange characteristics, ascorbate peroxidase, glutathione reductase and catalase activities, and levels of hydrogen peroxide and formate were determined. Carbon dioxide assimilation rates were inhibited after the addition of aminotriazole: photorespiratory conditions exacerbated this inhibition. Carbon dioxide response curves showed that aminotriazole reduced both the RuBP regeneration rate and the efficiency of the carboxylation reaction of Rubisco. Catalase activity was completely inhibited 200 min after the application of this inhibitor, but no concomitant increase in H2O2 concentration was found. Under enhanced photorespiratory conditions, H2O2 concentrations increased. This suggests that under normal environmental conditions hydrogen peroxide is metabolized via alternative mechanisms. The aminotriazole treatment had no effect on the ascorbate peroxidase and glutathione reductase activities, but caused a substantial increase in the formate pool size. These results suggest that hydrogen peroxide is metabolized by reacting with glyoxylate to produce formate and CO2. The increased production of formate may reduce the flow of carbon through the normal photorespiratory pathway and may also be used anaplerotically as a precursor of products of 1 -C metabolism other than serine. This would prevent the return of photorespiratory carbon to the RPP pathway, leading to a smaller RuBP pool size which would in turn result in a decrease in carboxylation conductance (carboxylation efficiency) and regeneration rate of RuBP.

Reactive oxygen species promote chloroplast dysfunction and salicylic acid accumulation in fumonisin B1‐induced cell death

“…Together, our data demonstrate that FB1 can induce light-dependent ROS production at an early time point and then trigger PAL activation, which could initiate and regulate SA-mediated PCD. 3-AT has been widely used as a histidine synthesis inhibitor in yeast [43], while it acted as a reversible inhibitor of CAT in animal and plant cells, thus intracellular ROS accumulation can be achieved in our experiments by using this inhibitor [25,44,45]. Furthermore, we found that in contrast with the increase of PAL activity and PAL1 gene expression, SA accumulation in H 2 O 2 -treated leaves was higher than 3-AT treatment within 1-4 days (Fig.…”

Photorespiratory metabolism of glyoxylate and formate in glycine-accumulating mutants of barley and Amaranthus edulis

“…This is in accordance with the notion that glyoxylate is channelled within the peroxisomal matrix and does not readily leak out of the peroxisomes (Heupel et al 1991). While Amory et al (1992) found increased formate contents in pea leaves that had been incubated in low CO 2 , neither transfer of wild-type barley plants from elevated CO 2 into air nor illumination aected formate contents in our study (Figs. 2, 5).…”

The Molecular Biology and Metabolism of Glutathione

“…Both types of plant showed a marked accumulation of glutathione when plants were transferred to 'photorespiratory' conditions (Smith et al 1984, Willekens et al 1997. Similar accumulation of glutathione has been observed when leaves are treated with catalase inhibitors (Smith 1985, Amory et al 1992). These effects may have considerable physiological relevance since catalase undergoes continuous turnover in the light.…”