Long-Term Anaerobic Metabolism in Root Tissue (Metabolic Products of Pyruvate Metabolism)

Abstract

Vanlerberghe et al. (1990) have recently shown that the green alga Selenastrum minutum accumulates succinate under anaerobic conditions. They demonstrate that the OAA required for reduction to succinate is initially provided by transferring the amino group of aspartate to pymvate to provide a 2-fold increase in ATP yield per hexose as com- One of the difficulties with most of the studies on anaerobic metabolism in plants is that they are restricted to short time intervals, usually a maximum of 12 to 24 h Ranson, 1967% 1967b;Hoffman et al., 1986;Vanlerberghe et al., 1990;Roberts et al., 1992). However, since barley (Hordeum vulgare L.) and maize can usually survive 3 to 5 d of anaerobic stress (Harberd and Edwards, 1982;Lemke-Keyes and Sachs, 1989), it may be the long-term adaptations to anaerobic stress that are more important in determining sensitivity to flooding.In this study, we looked at the long-tem effects of anaeroshort-term effects. We show that although a number of metabolic products, lactate, Ala, malate, and succinate, accumulate during short-term anaerobiosis, they do not continue to increase during long-term anaerobiosis. We also examined the effect on the accumulation of metabolites of reducing both the leve1 of available nitrogen and the accumulation of ethanol by using an ADH-mutant. Finally, we 'Ooked at 'Ome Of the enzYmes involved in and wccinate production to determine whether anY Of these enzYmes are induced der anaerobic COnditions. 1988, 1989).Under hypoxic or anaerobic conditions, there are changes in the levels of glycolytic intermediates in roots and an increased glycolytic flux (the Pasteur effect) (Faiz-ur-Rahman occur so that the cell can meet its requirements for ATP despite the much lower efficiency of ATp production by fermentation. The increase in glycolytic flux &ring hypoxia is accompanied by the accumulation of a number of glycolytic end products including ethanoI, lactate, AIa, and various organic acids and amino acids (Effer and R~~~~~, 196713;Gfeller and Gibbs, 1984;Roberts et al., 1984;Hoffman et al., 1986;Roberts et al., 1992). A number of alternative pathways to lactate and ethanol fermentation have been discovered in animals with high resistance to anoxia. These animals accumulate combinations of a number of end products including Ala, octopine, alanopine, acetate, propionate, 2-methyl-b~-tyrate, and succinate (Fields, 1983). The advantages of these alternative strategies for anaerobic fermentation are based on an increased ATP production per mo1 of substrate fermented, the production of NAD+ to provide a net sink for reductant, and the maintenance of the cellular pH. Davies, 1980

Nitrite Reduces Cytoplasmic Acidosis under Anoxia

“…3A), and although the amounts decreased for segments taken from seedlings pretreated with nitrate, none of the changes were significant. Succinate accumulation is a common response to short-term anoxia in roots (Roberts et al, 1992;Good and Muench, 1993), and in the absence of nitrate, the level of succinate in the suspending medium was the same at the end of a 6-h anoxic incubation as the level of lactate. The bulk of the succinate in the suspending medium was released in the first hour of the experiment (data not shown), in agreement with the effect of anoxia on carbon metabolism in maize root tips (Roberts et al, 1992).…”

Amino acids as indicators of physiological stress in common reed Phragmites australis affected by an extreme flood

“…The advantage of this pathway is that the anaerobic ATP production is combined with the avoidance of cytosolic acidification (Roberts et al, 1992;Crawford et al, 1994) and the assimilation of nitrogen (Kohl and Henning, 1987). The accumulation of alanine and serine in addition to Gaba in response to anaerobic metabolism has been described in various plant species, including P. australis (Kohl and Henning, 1987;Haldemann and Brändle, 1988;Good and Muench, 1993;Rolletschek et al, 1998). In this study, an increase of the amino acids Ala, Ser and Gaba was identified in extremely damaged reed stands within Lake Constance, indicating oxygen deprivation, whilst the percentage of Asn decreased.…”

“…Such products are removed from the metabolism by transamination of pyruvate and 3-phosphoglycerate to alanine and serine. This leads to a weakening of the end product inhibition of the glycolysis so that the glycolytic metabolism is acce1erated (Good and Muench, 1993). The advantage of this pathway is that the anaerobic ATP production is combined with the avoidance of cytosolic acidification (Roberts et al, 1992;Crawford et al, 1994) and the assimilation of nitrogen (Kohl and Henning, 1987).…”

Combined Noninvasive Imaging and Modeling Approaches Reveal Metabolic Compartmentation in the Barley Endosperm

“…Ala is the characteristic and major free amino acid accumulated when plants are suffering from hypoxia, as shown here for barley ( Figure 2C) and as previously shown for Zea mays, Medicago truncatula, and Arabidopsis thaliana (Good and Muench, 1993;Muench and Good, 1994;Ricoult et al, 2005Ricoult et al, , 2006Miyashita et al, 2007). Ala synthesis relies on the reversible action of Ala-AT, with the direction of catalysis being able to flip rapidly, depending on the local conditions in planta Beatty et al, 2009).…”

“…While root-specific isoforms of Ala-AT and other homologs expressed in vegetative tissues respond to oxygen supply (Good and Crosby, 1989;Good and Muench, 1993;Miyashita et al, 2007), the endosperm-specific one does not (V. Radchuk, personal communication). A plausible interpretation is that in the endosperm, posttranslational regulation of Ala-AT activity is of particular significance.…”