Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons

Bellis, Luigi De; Picciarelli, Piero; Pistelli, Laura; Alpi, Amedeo

doi:10.1007/bf00198797

Cited by 45 publications

(47 citation statements)

References 16 publications

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“…More recently, an increase of some peroxisomal activities was found in senescing leaves (7,16) and carnation petals (10). Because sugar starvation occurs during the senescence of leaf tissues (19), it is possible that the stimulation of glyoxysomal or peroxisomal enzymes in senescing leaves or petals is specifically related to the situation of sugar starvation as it is in root tips.…”

Section: Discussionmentioning

confidence: 99%

Increased Fatty Acid β-Oxidation after Glucose Starvation in Maize Root Tips

Dieuaide¹,

Brouquisse²,

Pradet³

et al. 1992

Plant Physiol.

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The effects of glucose starvation on the oxidation of fatty acids were studied in excised maize (Zea mays L.) root tips. After 24 hours of glucose starvation, the rate of oxidation of palmitic acid to CO2 by the root tips was increased 2.5-fold. Different enzyme activities were tested in a crude particulate fraction from nonstarved root tips and those starved for 24 hours. It is usually thought that carbohydrates are the major respiratory substrates of plant cells, whereas lipids and proteins make a negligible contribution to the respiratory carbon flux (1). However, there is growing evidence that the carbohydrate reserves quickly decrease to low levels in darkness (4,20). This suggests that carbohydrates may become limiting, and the contribution of lipids and proteins to respiration increase, not only in senescing tissues (1) but also during the normal plant life.The metabolic consequences of carbohydrate starvation have been studied in a number of plant species. The depletion of intracellular carbohydrate is associated with a decrease of the respiration rate and a decline in the respiratory quotient from 1 to 0.75. After a long period of starvation, a delay is needed for the recovery of respiration (27) and fermentation (28). These results suggested that cellular components were degraded to sustain respiration. More recently, the decrease of total proteins and fatty acids and increasing levels of phosphorylcholine (9) and asparagine (12) provided more direct evidence for phospholipid and protein breakdown during sugar starvation in sycamore cells in culture. Similar results were obtained with maize root tips, in which proteins and fatty acids were also found to decrease during starvation (5). These results suggested that, during starvation, fatty acids would be degraded by ,8-oxidation, thus producing acetylCoA necessary to the tricarboxylic acid cycle. However the role of,-oxidation is not well established. This pathway has been generally associated with neoglucogenesis, but it has been recently shown that, in lettuce embryos, the ,8-oxidation of fatty acids directly feeds the tricarboxylic acid cycle, providing the substrate for respiration during the early steps of germination (29). It can be hypothesized that ,8-oxidation could play a similar role in sugar-starved tissues.The cellular localization of ,3-oxidation is still a matter of debate. It was considered as exclusively peroxisomal (14, 17), but previous works indicating a mitochondrial localization of 13-oxidation (33) have been recently reinforced (24). In the roots of maize seedlings (13), the activities of the four 13-oxidation enzymes have been previously detected in the peroxisomal, not in the mitochondrial, fraction.The aim of the present work was to determine whether the overall 13-oxidation pathway was functional in maize root tips and to compare the peroxisomal 1-oxidation and glyoxylic cycle activities before and after a starvation treatment. Our results indicate that the 13-oxidation of palmitic acid is active in maize root tips and...

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Section: Discussionmentioning

confidence: 99%

Increased Fatty Acid β-Oxidation after Glucose Starvation in Maize Root Tips

Dieuaide¹,

Brouquisse²,

Pradet³

et al. 1992

Plant Physiol.

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“…The source of carbon for sucrose synthesis in this case is unlikely to be photosynthesis, but is rather through the P-oxidation of lipids because glyoxysomal pathways are known to increase during senescence (Gut and Matile, 1988;DeBellis et al, 1990). In this regard, the metabolite repression model has previously been suggested for the senescence-associated expression of malate synthase in cucumber cotyledons (Graham et al, 1992).…”

Section: (C) Rbcs (D) Ef-1a (E) Sag2 (F)sag4mentioning

confidence: 91%

Developmental and age-related processes that influence the longevity and senescence of photosynthetic tissues in arabidopsis.

et al. 1993

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Factors that influence the longevity and senescence of photosynthetic tissues of Arabidopsis were investigated. To determine the influence of reproductive development on the timing of somatic tissue senescence, the longevity of rosette leaves of the Landsberg efecta strain and of isogenic mutant lines in which flowering is delayed (co-2) or sterile flowers are produced (ms7-7) were compared. No difference in the timing of senescence of individual leaves was observed between these lines, indicating that somatic tissue longevity is not governed by reproductive development in this species. To examine the role of differential gene expression in the process of leaf senescence, cDNA clones representing genes that are differentially expressed in senescing tissues were ísolated. Sequence analysis of one such clone indicated homology to previously cloned cysteine proteinases, which is consistent with a role for the product of this gene in nitrogen salvage. RNA gel blot analysis revealed that increased expression of senescence-associated genes is preceded by declines in photosynthesis and in the expression of photosynthesis-associated genes. A model is presented in which it is postulated that leaf senescence is triggered by age-related declines in photosynthetic processes.

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“…The glyoxylate cycle enzymes isocitrate lyase and malate synthase are localized in glyoxysomes and play a role in lipid mobilization, both in postgerminative seedlings and in senescent plant tissues (Beevers, 1979;Huang et al, 1983;Trelease and Doman, 1984;Gut and Matile, 1988;De Bellis et al, 1990;De Bellis and Nishimura, 1991). We have shown that genes encoding the two enzymes are transcriptionally active in pollen (Fig.…”

Section: Genes Encoding Glyoxysomal Enzymes Are Expressed In Pollenmentioning

confidence: 99%

“…In plants with cotyledons that become photosynthetically active, the levels of the glyoxylate cycle enzymes decrease and those of the photorespiratory enzymes increase as glyoxysomes are converted into leaf-type peroxisomes when seedlings undergo the transition from heterotrophic to autotrophic growth (Trelease et al, 1971;Becker et al, 1978;Titus and Becker, 1985;Nishimura et al, 1986;Sautter, 1986). Glyoxylate cycle enzyme levels also increase during the senescence of green cotyledons, leaves, and petals as leaf-type peroxisomes are transformed to glyoxysomes, presumably to function in the breakdown of membrane lipids (Gut and Matile, 1988;De Bellis et al, 1990;Landolt and Matile, 1990;De Bellis and Nishimura, 1991;Pistelli et al, 1991;Graham et al, 1992). Thus, glyoxysomal function is induced at several developmental stages.…”

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confidence: 99%

Isocitrate Lyase and Malate Synthase Genes from Brassica napus L. Are Active in Pollen

Zhang

Laudencia‐Chingcuanco

Comai

et al. 1994

Plant Physiol.

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To investigate if pollen possesses glyoxysomal function, we analyzed the activities of isocitrate lyase and malate synthase genes. Because the activities of these enzymes were exceedingly low in pollen extracts, we constructed fusion genes encoding j3-glucuronidase (CUS) that are regulated by isocitrate lyase or malate synthase promoters from Brassica napus L. to increase the sensitivity of our assays. Expression of the fusion genes in transgenic tobacco was qualitatively similar to that of the endogenous genes; CUS activity was low in dry seeds, maximal in seedlings, and very low or undetectable in leaves, indicating that the promoters are regulated correctly. We showed that isocitrate lyase and malate synthase genes are active at specific stages of pollen development and that their activities are not enhanced during pollen germination in transgenic tobacco. We also confirmed that the endogenous genes are active by showing that the corresponding mRNAs could be detected in pollen at specific stages of development. The activation of the isocitrate lyase and malate synthase genes suggests that glyoxysomal function is induced during pollen development.Glyoxysomes are specialized peroxisomes that play a pivotal role in the postgerminative growth of oilseed plants (Beevers, 1979;Huang et al., 1983;Trelease and Doman, 1984). These organelles contain the glyoxylate cycle and /3-oxidation enzymes that catalyze the net conversion of fatty acids into succinate and, thus, account for the ability of plants to utilize lipids as a carbon source for carbohydrate synthesis. The carbohydrates generated as a result of these reactions serve as nutrients for seedlings until they become photosynthetically active.Glyoxysomal function is induced at several stages of the plant life cycle when peroxisomes with different metabolic roles are converted into glyoxysomes. The induction of glyoxysomal function is generally monitored using two key glyoxylate cycle enzymes, isocitrate lyase and malate synthase, which are required for glyoxysomal function and are associated exclusively with glyoxysomes (reviewed by Olsen and

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Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons

Cited by 45 publications

References 16 publications

Increased Fatty Acid β-Oxidation after Glucose Starvation in Maize Root Tips

Increased Fatty Acid β-Oxidation after Glucose Starvation in Maize Root Tips

Developmental and age-related processes that influence the longevity and senescence of photosynthetic tissues in arabidopsis.

Isocitrate Lyase and Malate Synthase Genes from Brassica napus L. Are Active in Pollen

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