Regulation of levels of proline as an osmolyte in plants under water stress

• Published in: Plant and cell physiology Vol. 38; no. 10; pp. 1095 - 1102
• Main Authors: Yoshiba, Y. (Hitachi Ltd., Hatoyama, Saitama (Japan)), Kiyosue, T, Nakashima, K, Shinozaki, K.Y, Shinozaki, K
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.10.1997
• Subjects: 1-Pyrroline-5-Carboxylate Dehydrogenase; Abscisic acid; Agronomy. Soil science and plant productions; biochemical pathways; Biological and medical sciences; biosynthesis; chemical constituents of plants; chemical reactions; delta-1-Pyrroline-5-Carboxylate Reductase; drought; DROUGHT STRESS; Economic plant physiology; enzyme activity; ESTRES DE SEQUIA; Forecasting; Fundamental and applied biological sciences. Psychology; Gene Expression; genetic engineering; genetics; glutamic acid; metabolism; Nicotiana tabacum; osmoregulation; OSMOTIC PRESSURE; oxidoreductases; Oxidoreductases Acting on CH-NH Group Donors; Oxidoreductases Acting on CH-NH Group Donors - genetics; plant physiology; Plant physiology and development; PLANTAS; PLANTE; PLANTS; Plants - genetics; Plants - metabolism; PRESION OSMOTICA; PRESSION OSMOTIQUE; PROLINA; PROLINE; Proline - biosynthesis; Proline - metabolism; Proline dehydrogenase (oxidase) (EC 1.5.99.8); Proline Oxidase; Proline Oxidase - genetics; Pyrroline Carboxylate Reductases; Pyrroline Carboxylate Reductases - genetics; rehydration; salinity; STRESS DU A LA SECHERESSE; stress response; transcription (genetics); Transcriptiponal regulation; transgenic plants; Water; Water and solutes. Absorption, translocation and permeability; Water relations, transpiration, stomata; Water stress; Water-Electrolyte Balance; Δt-pyrroline-5-carboxy-late synthetase; 1-Pyrroline-5-carboxylate dehydrogenase; Vegetals; Enzyme; Osmoregulation; Proline; Metabolic pathway; Review; Gene expression; Metabolism; Water stress; Regulation(control); Oxidoreductases; Biological accumulation; Proline dehydrogenase
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/oxfordjournals.pcp.a029093

Compatible osmolytes are potent osmoprotectants that play a role in counteracting the effects of osmotic stress. Proline (Pro) is one of the most common compatible osmolytes in water-stressed plants. The accumulation of Pro in dehydrated plants is caused both by activation of the biosynthesis of Pro and by inactivation of the degradation of Pro. In plants, L-Pro is synthesized from L-glutamic acid (L-Glu) via delta(1)-pyrroline-5-carboxylate (P5C) by two enzymes, P5C synthetase (P5CS) and P5C reductase (P5CR). L-Pro is metabolized to L-Glu via P5C by two enzymes, proline dehydrogenase (oxidase) (ProDH; EC 1.5.99.8) and P5C dehydrogenase (P5CDH; EC 1.5.1.12). Such metabolism of Pro is inhibited when Pro accumulates during dehydration and it is activated when rehydration occurs. Under-dehydration conditions, when expression of the gene for P5CS is strongly induced, expression of the gene for ProDH is inhibited. By contrast, under rehydration conditions, when the expression of the gene for ProDH is strongly induced, the expression of the gene for P5CS is inhibited. Thus, P5CS, which acts during the biosynthesis of Pro, and ProDH, which acts during the metabolism of Pro, appear to be the rate-limiting factors under water stress. Therefore, it is suggested that levels of Pro are regulated at the level of transcriptional the genes of these two enzymes during dehydration and rehydration. Moreover, it has been demonstrated that Pro acts as an osmoprotectant and that overproduction of Pro results in increased tolerance to osmotic stress of transgenic tobacco plants. Genetically engineered crop plants that overproduce Pro might, thus, acquire osmotolerance, namely, the ability to tolerate environmental stresses such as drought and high salinity