Abstract
Excised maize (Zea mays L.) root tips were used to monitor the effects of prolonged glucose starvation on nitrogen metabolism. Following root-tip excision, sugar content was rapidly exhausted, and protein content declined to 40 and 8% of its initial value after 96 and 192 h, respectively. During starvation the contents of free amino acids changed. Amino acids that belonged to the same “synthetic family” showed a similar pattern of changes, indicating that their content, during starvation, is controlled mainly at the level of their common biosynthetic steps. Asparagine, which is a good marker of protein and amino-acid degradation under stress conditions, accumulated considerably until 45 h of starvation and accounted for 50% of the nitrogen released by protein degradation at that time. After 45 h of starvation, nitrogen ceased to be stored in asparagine and was excreted from the cell, first as ammonia until 90–100 h and then, when starvation had become irreversible, as amino acids and aminated compounds. The study of asparagine metabolism and nitrogen-assimilation pathways throughout starvation showed that: (i) asparagine synthesis occurred via asparagine synthetase (EC 6.3.1.1) rather than asparagine aminotransferase (EC 2.6.1.14) or the β-cyanoalanine pathway, and asparagine degradation occurred via asparaginase (EC 3.5.1.1); and (ii) the enzymic activities related to nitrogen reduction and assimilation and amino-acid synthesis decreased continuously, whereas glutamate dehydrogenase (EC 1.4.1.2–4) activities increased during the reversible period of starvation. Considered together, metabolite analysis and enzymic-activity measurements showed that starvation may be divided into three phases: (i) the acclimation phase (0 to 30–35 h) in which the root tips adapt to transient sugar deprivation and partly store the nitrogen released by protein degradation, (ii) the survival phase (30–35 to 90–100 h) in which the root tips expel the nitrogen released by protein degradation and starvation may be reversed by sugar addition and (iii) the cell-disorganization phase (beyond 100 h) in which all metabolites and enzymic activities decrease and the root tips die.
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Abbreviations
- AlaAT:
-
alanine aminotransferase
- AspAT:
-
aspartate aminotransferase
- AS:
-
asparagine synthetase
- Asnase:
-
asparaginase
- AsnAT:
-
asparagine aminotransferase
- β-CS:
-
β-cyanoalanine synthase
- GDH:
-
glutamate dehydrogenase
- Glnase:
-
glutaminase
- GOGAT:
-
glutamate synthase
- GS:
-
glutamine synthetase
- NiR:
-
nitrite reductase
- NR:
-
nitrate reductase
Referencess
Baysdorfer, C., Warmbrodt, R.D., Van Der Woude, W.J. (1988) Mechanisms of starvation tolerance in Pearl millet. Plant Physiol. 88, 1381–1387
Bowsher, C.G., Long, D.M., Oaks, A., Rothstein, S.J. (1990) Effect of light/dark cycles on expression of nitrate assimilatory genes in maize roots. Plant Physiol. 95, 281–285
Brouquisse, R., James, F., Raymond, P., Pradet, A. (1991) Study of glucose starvation in excised maize root tips. Plant Physiol. 96, 619–626
Bryan, J.K. (1990) Advances in the biochemistry of amino acid biosynthesis. In: The biochemistry of plants, vol. 16, pp. 161–196, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Cammaerts, D., Jacobs, M. (1985) A study of the role of glutamate dehydrogenase in the nitrogen metabolism of Arabidopsis thaliana. Planta 163, 517–526
Caro, L.H.P., Plomb, P.J.A.M., Leverve, X.M., Meijer, A.J. (1989) A combination of intracellular leucine with either glutamate or aspartate inhibits autophagic proteolysis in isolated rat hepatocytes. Eur. J. Biochem. 181, 717–720
Clarkson, D.T. (1986) Regulation of the absorption and release of the nitrate by plant cells: a review of current ideas and methodology. In: Fundamental, ecological and agricultural aspects of nitrogen metabolism in higher plants, pp. 3–27, Lambers, H., Neeteson, J.J., Stulen, I., eds. Martinus Nijhoff, Dordrecht
Dieuaide, M., Brouquisse, R., Pradet, A., Raymond, P. (1992) Increased fatty acid β-oxidation after glucose starvation in maize root tips. Plant Physiol. 99, 595–600
Flores, H.E. (1990) Polyamines and plant stresses. In: Stress responses in plants: adaptation and acclimation mechanisms, pp. 217–239, Alscher, R.G., Cumming, J.R., eds. Wiley-Liss, New York
Frossard, J.S. (1985) L'éclairement du feuillage, facteur de régulation du rythme nycthéméral de la respiration des racines. Physiol. Vég. 23, 163–173
Genix, P., Bligny, R., Martin, J.B., Douce, R. (1990) Transient accumulation of asparagine in sycamore cellsd after a long period of sucrose starvation. Plant Physiol. 94, 717–722
Gerbling, H., Gerhardt, B. (1989) Peroxysomal degradation of branched-chain 2-oxo acids. Plant Physiol. 91, 1387–1392
Givan, C.V. (1979) Metabolic detoxification of ammonia in tissue of higher plants. Phytochemistry 18, 375–382
Givan, C.V. (1980) Aminotransferases in higher plants. In: The biochemistry of plants, vol. 5, pp. 329–357, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Graves, L.M., Switzer, R.L. (1990) Aspartokinase II from Bacillus subtilis is degraded in response to nutrient limitation. J. Biol. Chem. 265, 14947–14955
Hendrickson, H.R., Conn, E.E. (1969) Cyanide metabolism in higher plants — IV. Purification and properties of the β-cyanoalanine synthase of blue lupine. J. Biol. Chem. 244, 2632–2640
Ireland, R. (1990) Amino acid and ureide biosynthesis. In: Plant physiology, biochemistry and molecular biology, pp. 407–421, Dennis, D.T., Turpin, D.H., eds. Longman Scientific and Technical, Harlow
Joseph, M.H., Marsden, C.A. (1986) Amino acids and small peptides. In: HPLC of small molecules — A practical approach, pp. 13–28, Lim, C.K., ed. IRL press, Oxford
Journet, E.P., Bligny, R., Douce, R. (1986) Biochemical changes during sucrose deprivation in higher plant cells. J. Biol. Chem. 261, 3193–3199
Joy, K.W., Ireland, R. (1990) Enzymes of asparagine metabolism. In: Methods in plant biochemistry, vol. 3, pp. 287–296, Lea, P.J., ed. Academic Press, London
Kerr, P.S., Rufty, Jr, T.W., Huber, S.C. (1985) Changes in nonstructural carbohydrates in different parts of soybean (Glycine max [L.] Merr.) plants during a light/dark cycle and in extended darkness. Plant Physiol. 78, 576–581
King, G.A., Woollard, D.C., Irving, D.E., Borst, W.M. (1990) Physiological changes in asparagus spear tips after harvest. Physiol. Plant. 80, 393–400
Kleinhofs, A., Warner, R.L. (1990) Advances in nitrate assimilation. In: The biochemistry of plants, vol. 16, pp. 89–120, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Lea, P.J., Robinson, S.A., Stewart, G.R. (1990) The enzymology and metabolism of glutamine, glutamate and asparagine. In: The biochemistry of plants, vol. 16, pp. 121–159, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Lee, R.B., Ratcliffe, R.G. (1991) Observation of the subcellular distribution of the ammonium ion in maize root tissue using in-vivo 14N-nuclear magnetic resonance spectroscopy. Planta 183, 359–367
Long, D.M., Oaks, A. (1990) Stabilization of nitrate reductase in maize roots by chymostatin. Plant Physiol. 93, 846–850
Loyola-Vargas, V.M., Sanchez de Jimenez, E. (1984) Differential role of glutamate dehydrogenase in nitrogen metabolism of maize tissues. Plant Physiol. 76, 536–540
MacGrath, R.B., Coruzzi, G.M. (1991) A gene network controlling glutamine and asparagine biosynthesis in plants. Plant J. 1, 275–280
Mazelis, M. (1980) Amino acid catabolism. In: The biochemistry of plants, vol. 5, pp. 541–567, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Mortimore, G.E., Wert, J.J., Adams, C.E. (1988) Modulation of the amino acid control of hepatic protein degradation by caloric deprivation. J. Biol. Chem. 263, 19545–19551
Oaks, A., Ross, D.W. (1983) Asparagine synthetase in Zea Mays. Can. J. Bot. 62, 68–73
Oaks, A., Jones, K., Misra, S. (1979) A comparison of glutamate synthase obtained from maize endosperm and roots. Plant Physiol. 63, 793–795
Oaks, A., Stulen, I., Jones, K., Winspear, M.J., Misra, S., Boesel, I.L. (1980) Enzymes of nitrogen assimilation in maize roots. Planta 148, 477–484
O'Neal, D., Joy, K.W. (1973) Glutamine synthetase of pea leaves. I. Purification, stabilization and pH optima. Arch. Biochem. Biophys. 159, 113–122
Pate, J.S., Layzell, D.B. (1990) Energetics and biological costs of nitrogen assimilation. In: The biochemistry of plants, vol. 16, pp. 1–42, Stumpf, P.K., Conn, E.E., eds. Academic Press, London
Patel, D.D., Barlow, P.W., Lee, R.B. (1990) Development of vacuolar volume in the root tips of pea. Annals Bot. 65, 159–169
Peoples, M.B., Dalling, M.J. (1988) The interplay between proteolysis and amino acid metabolism during senescence and nitrogen reallocation. In: Senescence and aging in plants, pp. 181–217, Nooden, L.D., Leopold, A.C., eds. Academic Press, London
Postius, C., Klemme, B., Jacobi, G. (1976) Dark starvation and plant metabolism. V. Comparative studies on the alteration of enzyme activities during dark starvation and senescence. Z. Pflanzenphysiol. 78, 122–132
Pradet, A., Raymond, P. (1983) Adenine nucleotide ratios and adenylate energy charge in energy metabolism. Annu. Rev. Plant Physiol. 34, 199–224
Rej, R., Horder, M. (1983a) Aspartate aminotransferase. In: Methods of enzymatic analysis, vol. 3, pp. 416–433, Bergmeyer, H.U. ed. V.C.H., Weinheim
Rej, R., Horder, M. (1983b) Alanine aminotransferase.In: Methods of enzymatic analysis, vol. 3, pp. 444–456, Bergmeyer, H.U. ed., V.C.H., Weinheim
Roby, C., Martin, J.B., Bligny, R., Douce, R. (1987) Biochemical changes during sucrose deprivation in higher plant cells. 31-P nuclear magnetic resonance studies. J. Biol. Chem. 262, 5000–5007
Rognes, S.E. (1980) Anion regulation of lupin asparagine synthetase: chloride activation of the glutamine-utilizing reactions. Phytochemistry 19, 2287–2293
Saglio, P.H., Pradet, A. (1980) Soluble sugars, respiration and energy charge during aging of excised maize root tips. Plant Physiol. 66, 516–519
Sahulka, J., Lisa, L. (1978) The influence of exogenously supplied sucrose on glutamine synthetase and glutamate dehydrogenase levels in excised Pisum sativum roots. Biol. Plant. 20, 446–452
Sieciechowicz, K.A., Joy, K.W., Ireland, R.J. (1988a) The metabolism of asparagine in plants. Phytochemistry 27, 663–671
Sieciechowicz, K.A., Joy, K.W., Ireland, R.J. (1988b) Diurnal changes in asparaginase activity in pea leaves. J. Exp. Bot. 39, 695–706
Singh, R.P., Srivastava, H.S. (1983) Regulation of glutamate dehydrogenase activity by amino acids in maize seedlings. Physiol. Plant. 57, 549–554
Srivastava, H.S., Singh, R.P. (1987) Role and regulation of glutamate dehydrogenase activity in higher plants. Phytochemistry 26, 597–610
Stitt, M., ap Rees, T. (1978) Pathways of carbohydrates oxidation in leaves of Pisum sativum and Triticum aestivum. Phytochemistry 17, 1251–1256
Stulen, I., Oaks, A. (1977) Asparagine synthetase in corn roots. Plant Physiol. 60, 680–683
Stulen, I., Israelstam, G.F., Oaks, A. (1979) Enzymes of asparagine synthesis in maize roots. Planta 146, 237–241
Suzuki, A., Oaks, A., Jacquot, J-P., Vidal, J., Gadal, P. (1985) An electron transport system in maize roots for reactions of glutamate synthase and nitrite reductase. Plant Physiol. 78, 374–378
Szweda, L.I., Atkinson, D.E. (1990) Response of rat liver glutaminase to pH, ammonium and citrate. J. Biol. Chem. 265, 20869–20873
Tirado, J-L., Conéjéro, G., Robin, P. (1990) Comparaison des activités glutamine synthétase, glutamate déshydrogénase et nitrite réductase chez Glycine max. Effet de l'obscurité sur la première feuille trifoliée. Plant Physiol. Biochem. 28, 251–257
Thomas, H. (1978) Enzymes of nitrogen mobilization in detached leaves of Folium temulentum during senescence. Planta 142, 161–169
Tsai, F-Y., Coruzzi, G.M. (1990) Dark-induced and organ-specific expression of two asparagine synthetase genes in Pisum sativum. EMBO J. 9, 323–332
Urquhart, A.A., Joy, K.W. (1981) Use of phloem exudate technique in the study of amino acid transport in pea plant. Plant Physiol. 68, 750–754
Veierskov, B., Satler, S.O., Thimann, K.V. (1985) Metabolism of oat leaves during senescence. VIII The role of serine in modifying senescence. Plant Physiol. 78, 315–319
Wallace, W., Shannon, J.D. (1981) Proteolytic activity and nitrate reductase inactivation in maize seedlings. Aust. J. Plant Physiol. 8, 211–219
Watford, M., Smith, E.M., Erbelding, E.J. (1984) The regulation of phosphate-activated glutaminase activity and glutamine metabolism in the streptozotocin-diabetic rat. Biochem J. 224, 207–214
Yemm, E.W. (1937) Respiration of barley plants. III Protein metabolism in starving leaves. Proc. R. Soc. London B 123, 243–273
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Brouquisse, R., James, F., Pradet, A. et al. Asparagine metabolism and nitrogen distribution during protein degradation in sugar-starved maize root tips. Planta 188, 384–395 (1992). https://doi.org/10.1007/BF00192806
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DOI: https://doi.org/10.1007/BF00192806