Regolazione dell'assorbimento dell'ammonio nell'alga unicellulare Cyanidium caldarium

Di Martino Rigano, Vittoria   ; Vona, Vincenza   ; Manzo, Luigi   ; Di Martino, Catello   ; Rigano, Carmelo

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 81 (1987) no. 3, pp. 305-315

Résumé

Cells of Cyanidium caldarium, a unicellular acidophilic thermophilic non-vacuolate red alga, cultivated in batch under conditions of excess ammonium assimilated ammonium at a rate of $0,32 \,\mu mol/h/mg$ cell dry weight, and assimilation was up to 85% inhibited in darkness. By contrast, cells grown in chemostat under conditions of nitrogen limitation assimilated ammonium at a 3-fold higher rate, and assimilation was only 34% inhibited in darkness. Assimilation of ammonium was linear with time with all type of cells and under all the conditions tested. Batch-grown cells submitted to conditions of nitrogen starvation attained, after about 72 h, a 3-fold higher capacity to assimilate ammonium; beside, these N-starved cells, like N-limited chemostat cells, assimilated ammonium also in the dark at a rate which was only 15% lower than in the light. After ammonium addition (and assimilation), the capacity of these cells to take up ammonium costantly decreased in the time during 7 h period of light/dark cycles. However, the loss of capacity was less pronounced in the light and it was almost total in the dark. It is suggested that these variations in the overall capacity and in the pattern of ammonium assimilation in light and darkness in cells submitted to different nitrogen conditions depend on control phenomena which involve the partecipation of two distinct uptake systems, or of two glutamine synthetase/glutamate synthase systems, sharing different regulatory properties.

Bibliographie

[1] P.J. Syrett e I. Morris (1963) - The inhibition of nitrate assimilation by ammonia in Chlorella, «Biochim. Biophys. Acta», 67, 566-575.

[2] B.R. Grant (1968) - The effect of carbon dioxide concentration and buffer system on nitrate and nitrite assimilation by Dunaliella tertiolecta, «J. Gen. Microbiol.», 54, 327-336.

[3] B.R. Grant e I.M. Turner (1969) - Light stimulated nitrate and nitrite assimilation in several species of algae, «Comp. Biochem. Physiol.», 29, 995-1004.

[4] A. Thacker e P.J. Syrett (1972) - The assimilation of nitrate and ammonium by Chlamydomonas reinhardii, «New Phytol.», 71, 423-433.

[5] E. Flores e M.G. Guerrero (1980) - Properties of nitrate utilization in Anacystis nidulans attributable to a nitrate transport system, in «Book of abstracts of II Congress FESPP Societad Espanola de Fisiologia Vegetal, Santiago de Compostela», p. 345.

[6] J.V. Cullimore e A.P. Sims (1981) - Pathway of ammonia assimilation in illuminated and darkned Chlamydomonas reinhardii, «Phytochemistry», 20, 933-940.

[7] F.J. Florencio e J.M. Vega (1983) - Utilization of nitrate, nitrite and ammonium by Chlamydomonas reinhardii. Photoproduction of ammonium, «Planta», 158, 288-293.

[8] V. Di Martino Rigano, A. Martello, C. Di Martino e C. Rigano (1985) - Effect of $C0_{2}$ and phosphate deprivation on the control of nitrate, nitrite and ammonium metabolism in Chlorella, «Physiol. Plant.», 63, 241-246.

[9] R. Eisele e W.R. Ullrich (1977) - Effect of glucose and $C0_{2}$ on nitrate uptake and coupled $0H^{-}$ flux in Ankistrodes musbraunii, «Plant. Physiol.», 59, 18-21.

[10] V. Di Martino Rigano, V. Vona, C. Di Martino e C. Rigano (1986) - Effect of darkness and $C0_{2}$ starvation on $NH_{4}^{+}$ and $N0_{3}^{-}$ assimilation in the unicellular alga Cyanidium caldarium, «Physiol. Plant.», 68, 34-38.

[11] V. Di Martino Rigano, V. Vona, C. Di Martino e C. Rigano (1987) - Regulatory aspects of $NH_{4}^{+}$ utilization in the acidophilic thermophilic unicellular red alga Cyanidium caldarium, «New Phytol.», 105, in press.

[12] D. Kleiner (1981) - The transport of $NH_{3}$ and $NH_{4}^{+}$ across biological membranes, «Biochim. Biophys. Acta», 639, 41-52.

[13] S. Boussiba, C.M. Resch e J. Gibson (1984) - Ammonia uptake and retention in some cyanobacteria, «Arch. Microbiol.», 138, 287-292.

[14] A.N. Rai, P. Powell e W.D.P. Stewart (1984) - Evidence for an ammonium transport system in free-living and symbiotic cyanobacteria, «Arch. Microbiol.», 137, 241-246.

[15] A. Jayakumar, I. Schulman, D. Mac Neil e E.M. Barnes Jr. (1986) - Role of the Escherichia coli glnALG operon in the regulation of ammonium transport, «J. Bacteriol.» , 166, 281-284.

[16] P.J. Syrett, K.J. Flynn, C.J. Molloy, G.K. Dixon, A.M. Peplinska e R.C. Cresswell (1986) - Effects of nitrogen deprivation on rates of uptake of nitrogeneous compounds by the diatom Phaeodactylumtri cornutum Bohlin, «New Phytol.», 102, 39-44.

[17] J. Schlee e E. Komor (1986) - Ammonium uptake by Chlorella, «Planta», 168, 232-238.

[18] W.R. Ullrich, M. Larsson, C.M. Larsson, S. Lesch e A. Novacky (1984) - Ammonium uptake in Lemna gibba G 1, related membrane potential changes, and inhibition of anion uptake, «Physiol Plant.», 61, 369-376.

[19] B.J. Miflin e P.J. Lea (1976) - The path of ammonia assimilation in the plant kingdom, «Trends Biochem. Sci.», 1, 103-106.

[20] J.M. Vega (1986) - Enzymology of the assimilation of ammonium in the green alga Chlamydomonas reinhardii. Advanced course on inorganic nitrogen metabolism. Book of abstracts, p. 89, Jarandilla de La Vera, Spagna.