Methods for determination of proline in plants mafiadoc. Proline biosynthesis and osmoregulation in plants request pdf. Osmotic stressinduced accumulation of proline, an important protective osmolyte in higher plants, is dependent on the expression of. Pyrroline5carboxylate synthase and proline biosynthesis. In plants, proline is synthesized mainly from glutamate, but not arginine or ornithine funck et al. Dorffling k, dorffling h, lesselich g 1993 in vitroselection and regeneration of hydroxyprolineresistant lines of winter wheat with increased proline content and. Growth and proline content in nacl stressed plants of. Osmoregulation is the active regulation of osmotic pressure to maintain the balance of water and electrolytes in an organism. Leprot1, a transporter for proline, glycine betaine, and.
Despite the importance of this pathway, however, the exact metabolic route and enzymes involved in the synthesis of proline in plants have not been unequivocally identified. Proline metabolism and transport in plant development. Effects of free proline accumulation in petunias under. Although much is now known about proline metabolism, some aspects of its biological functions are still unclear. The tissuespecific nature of proline biosynthesis suggests that this may be an important consideration in the production of transgenic plants capable of synthesising elevated levels of proline. In numerous plants under different type of stress, the concentration increments up to 80% of the amino acid pool. The most common osmolytes that play crucial role in osmoregulation are proline, glycinebetaine, polyamines, and sugars. Proline can be distinguished among all other amino acids due to its unique structure with its. The pathways involved in proline synthesis and degradation are regulated by multiple enzymes. Lightdependent induction of proline biosynthesis by. We also describe the role of proline in cellular homeostasis. Glutamate is an important amino acid and acts as a precursor for the biosynthesis of. Delauney and others published proline biosynthesis and osmoregulation in plants find, read and cite all the research you need on researchgate.
In higher plants, the osmotic stressinduced accumulation of proline is dependent on the expression of the enzymes. We compared pro levels in transgenic tobacco nicotiana tabacum plants expressing a wildtype form of vigna. Salinity and drought are the major osmotic stress limitations that affect plant growth and crop yield in agriculture worldwide. Proline biosynthesis is activated and its catabolism repressed during dehydration, whereas rehydration triggers the opposite regulation, 34.
High osmolality as the osmolality of the surrounding environment increases, turgor pressure drops and growth slows or halts. Proline biosynthesis in plants takes place in the chloroplast and cytoplasm, whereas degradation occurs in the mitochondria. Department of biology, the university of the west indies, cave hill campus, bridgetown. Mechanism of proline biosynthesis and role of proline. Glutamine synthetase in the phloem plays a major role in. The proline biosynthesis in living organisms springerlink. In spite of these facts, little is known about the introduction ionic mechanisms of osmoregulation in higher plant cells, and the data are controversial at times. Here, we discuss the compartmentalization of proline biosynthesis, accumulation and degradation in the cytosol, chloroplast and mitochondria. Proline synthesis has been associated with tissues undergoing rapid cell divisions, such as shoot. Gs catalyzes the atpdependent condensation of ammonium with glutamate to yield glutamine, which then provides nitrogen groups, either directly or via glutamate for the biosynthesis of all. Proline biosynthesis and osmoregulation in plants created date. Regulation of lproline biosynthesis, signal transduction, transport.
Hare pd, cress wa 1997 metabolic implications of stressinduced proline accumulation in plants. Overexpression of the gmdreb6 gene enhances proline. Salt stress encourages proline accumulation by regulating. Proline metabolism involves several subcellular compartments and contributes to the redox balance of the cell. Delauney and others published proline biosynthesis and osmoregulation in plants find, read and cite all the. The compartmentalization of ions in vacuoles was also more efficient in salttolerant than saltsensitive plants radic et al.
Computational predictions of common transcription factor. Hence, the precise role of proline with respect to stress tolerance and equivocal. The role of proline in osmoregulation in phytophthora. Read proline biosynthesis and osmoregulation in plants, the plant journal on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. Delauney department of biology, the university of the west indies, cave hill campus, bridgetown, barbados. As amino acid it is a structural component of proteins, but it also plays a role as compatible solute under environmental stress conditions. Delauney aj, verma dps 1993 proline biosynthesis and osmoregulation in plants. Roles of proline in plant adaptation to environmental. The p5cs gene is expressed at high levels in vigna leaves and is inducible in roots subjected to salt stress, suggesting that p5cs plays a key role in proline biosynthesis, leading to osmoregulation in plants. As shown in figure 1, 14clabeled proline can be taken up by mature pollen and by pollen after germination, indicating that respective transport.
Effect of salinity on osmolytes and relative water content. Proline pro accumulation is a common physiological response in many plants in response to a wide range of biotic and abiotic stresses. Manyinvestigators 39 have hypothesized that aclass ofsmall organic molecules glycine betaine, proline betaine, proline, and others found in scores of 1064 the metabolism ofthe putative osmoprotective molecules in plants has been studied in somedetail 1012. Other functions of proline accumulation have also been proposed, including statabilization of macromolecules, a sink of carbon and nitrogen for use after relief of water deficit 34, radical detoxification 5 and regulation of cellular redux status by proline metabolism 6. Pyrroline5carboxylate synthase p5cs is the key enzyme in the synthesis of proline and ornithine fig. Lproline accumulation in plants is a wellrecognized physiological reaction to osmotic stress prompted by salinity, drought and other abiotic stresses. We report here the isolation of a mothbean vigna aconitifolia cdna clone encoding a bifunctional enzyme, delta 1pyrroline5carboxylate. The alternative response mediated by plants in response to salinity and drought are principally proline accumulation which regulates stress combat strategies owing to sustainable production in the realm of agricultural production even under severe stress.
Proline biosynthesis and osmoregulation in plants delauney. Phytohormones regulate accumulation of osmolytes under. Osmoregulation, plasma membrane, ion trans similar conclusions were made by huang and redmann porters, vicia faba. Intracellular lproline levels in plants are administered by biosynthesis, catabolism and transport among cells and various compartments of cell. In this study, we evaluated proline accumulation profiles in roots, stems and leaves of jerusalem artichoke helianthus tuberosus l. Lightdependent induction of proline biosynthesis by abscisic acid. Effects of high proline accumulation on chloroplast and. Mitchell accumulate free proline pro under droughtstress conditions. Pdf role of proline in plant response to drought and salinity. In cell cultures of tobacco adapted to 428 mm nacl, proline represents over 80% of the free amino acid pool rhodes and handa, 1989.
Sodium, free amino acids and glycine betaine contents were determined in the last fully expanded leaf of plants stressed by daily irrigation with saline water 0. Osmoregulation is the active regulation of the osmotic pressure of an organisms body fluids, detected by osmoreceptors, to maintain the homeostasis of the organisms water content. Plants transpire by drawing water in from the soil through root hairs by osmotic pressure. Proline biosynthesis and osmoregulation in plants, the. One of the final products, proline, and the intermediate substrate, pyrroline5carboxylate p5c, have noteworthy properties related to redox balance and osmotic stress and have been the focus of numerous studies related with both human health and agriculture. It has been suggested that the feedback regulation of p5cs is lost in plants under stress conditions. Proline accumulation influenced by osmotic stress in.
Conversely, proline biosynthesis is carried out in peripheral tissues with high rates of protein synthesis. Proline responding1 plays a critical role in regulating. Osmoregulation of proline biosynthesis in arabidopsis thaliana. Of the osmoregulants and protectants discussed in this volume, trehalose, fructa. Overexpression of pvp5cs1 and pvp5cs2 improved the proline biosynthesis under normal and salt stress conditions, and an excess of proline produces toxic action to plants which result in ornithine, as a precursor, entering the synthesis pathway of pas. These compounds stabilize the osmotic di erences between surroundings of cell and the cytosol. Regulation of lproline biosynthesis, signal transduction. Proline biosynthesis and osmoregulation in plants ashton j. Frontiers proline accumulation influenced by osmotic. Proline metabolism is modulated by differential regulation of organ specific.
The proline biosynthesis pathway in plants involves the participation of two key enzymes, pyrroline5carboxylate reductase p5cr and pyrroline5carboxylate synthetase p5cs fig. Macromolecular biosynthesis is inhibited and respiration. Proline metabolism in plants as sensors of abiotic. We also examined htp5cs, htoat and htpdh enzyme activities and gene expression patterns of putative htp5cs1, htp5cs2, htoat, htpdh1, and htpdh2. To maintain proper fluid balance and turgidity, plants osmoregulate by opening and closing stoma to control the transpiration of water. In summary, proline metabolism is in cooperation with polyamines metabolism in switchgrass. Thus accumulation of osmolyte compounds, usually called osmotic adjustment. Many plants synthesize and accumulate proline in response to osmotic stress. Controversy has surrounded the possible roles of proline. These phenomena are described as osmoregulation and osmotic. Proline accumulates in many plant species in response to environmental stress. Droughtinduced accumulation of soluble sugars and proline. Ec not assigned is the ratelimiting enzyme in proline pro biosynthesis in plants and is subject to feedback inhibition by pro.
A study of proline metabolism in canola brassica napus l. Stimulation of proline synthesis by abscisic acid aba and salt stress correlates with a striking activation. Frontiers proline biosynthesis enzyme genes confer salt. This allows the differential regulation of both pathways. The proline accumulated in response to water stress or salinity stress in plants is primarily localized in the cytosol leigh et al, 1981. Implications for agriculture, american zoologist, volume 41, issue 4. P5cs, which catalyzes the first two reactions of proline biosynthesis, is a bifunctional enzyme containing both the. Control of osmotic pressure is needed to perform biochemical reactions and preserve homeostasis. In these tissues, proline synthesis is controlled through the second enzyme of the route, pyrroline5carboxylate reductase p5cr, which is inhibited by proline. Proline accumulation is an important mechanism for osmotic regulation under salt stress. The high proline content present in mature pollen grains could be derived either from endogenous biosynthesis or from sporophytic supply of proline.
Difusion osmoregulation of proline biosynthesis in. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. Read proline biosynthesis and osmoregulation in plants, the plant journal on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Main pathway of proline synthesis in higher plants. B, concentrations of gly betaine or dmsp measured in chloroplasts isolated from leaves of salttolerant plants grown in nonsaline black bars or saline white bars conditions. Loss of function of pro1 showed inhibited proline biosynthesis. It is therefore believed that pro acts as an osmoprotectant in plants subjected to drought conditions. A bifunctional enzyme delta 1pyrroline5carboxylate. Proline responding1, gene encoding a p5cs catalyzing the biosynthesis of proline from glutamic acid, plays a critical role in regulating general protein synthesis and the cell cycle in maize wang et al. Osmoregulation is the active regulation of the osmotic pressure of an organisms fluids to maintain the homeostasis of the organisms water content. A, chemical structures of betaines and related compounds that occur in flowering plants and marine algae.