International Journal of Biochemistry. 199 (2017) 544-545 https://sites.google.com/site/photonfoundationorganization/home/international-journal-of-biochemistry Original Research Article. ISJN: 4438-5728: Impact Index: 4.52

International Journal of Biochemistry

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Proline: The Plant Protectant Kalpna Bhandari* Laboratory of Plant Physiology and Biotechnology, University Department of Botany, Ranchi University, Ranchi-834008, India

Article history: Received: 11 July, 2017 Accepted: 17 July, 2017 Available online: 04 September, 2017 Corresponding Author: Kalpna Bhandari* Email: kalpna.bhandari ( at ) gmail ( dot ) com Citation: Bhandari K*., 2017. Proline: The Plant Protectant. International Journal of Biochemistry. Photon 199, 544-545 All Rights Reserved with Photon. Photon Ignitor: ISJN44385728D872004092017

1. Introduction Proline is a non-essential imino acid i.e. having imino group (-NH) instead of usual amino group (NH2) and plays numerous protective functions in the plants. Biosynthesis It occurs in higher plants and is synthesised via pathway involving both glutamic acid (Glu) and ornithine (Orn) pathways. Its immediate precursor is imino acid (S)-1-pyrroline-5-carboxylate (P5C). Various enzymes involved in the biosynthesis are: a) Glutmate-1-kinase, glutamate-5-kinase b) Glutamate dehydrogenase c) Pyrroline-5-carboxylate synthetase (P5CS) d) Pyrroline-5-carboxylate reductase (P5CR). Protective functions in plants Proline acts as an important plant osmoprotectant under abiotic and biotic stress conditions (Hare and Cress, 1997; Bhandari and Nayyar, 2014) especially under drought, salinity and chilling Ph ton

stress. Proline as an important biomolecule, has been assigned various roles such as antioxidant by scavenging hydroxyl radical (Matysik et al. 2002), regulating NAD+/NADH ratio (Alia and Saradhi, 1993) protein stablising hydrotope (Srinivas and Balasubramanium, 1995), osmoregulation, stabilization of enzymes and biomembranes including conservation of energy and amino acids for post stress growth (Aspinall et al. 1981). When subjected to cold acclimation, Solanum hybrids showed increase in proline content (Van Swaij et al. 1985). In Glycine max also, proline content was found to be higher in the acclimated plants than non-acclimated ones and former also showed faster recovery as well thus proving protective role of proline under stress conditions (Yadeghari et al. 2008). Proline along with other cryopotectants like glycine betaine can confer tolerance to oxidative and heavy metal stress. Proline when exogenously applied to tobacco culture cells resulted in decreased lipid peroxidation but increased

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superoxide dismutase and catalase activities (Islam et al. 2009). When subjected to salt stress, the tobacco culture cells showed alleviation in the inhibition of catalase and peroxidase activities; the ability of proline to confer salt tolerance has been found to be higher than that of betaine possibly because of increased activities of anti-oxidation enzymes (Hoque et al., 2007). Potato hybrids when subjected to cold stress were found to have elevated levels of proline in the leaves (Van Swaaij et al., 1985). Glycine max plants when acclimated by subjecting the plants to non-lethal temperature of 4°C showed increased levels of proline and the non-acclimated plants also recovered slowly as compared to the acclimated ones. Proline levels varied during various phases i.e. increased in the acclimation phase, decreased in the chilling phase and then again showed increase in the recovery phase (Yadeghari et al., 2008). Proline imparts protective effect not only by acting as an effective cryoprotectant but also has some additional functions as well viz., stabilisation of proteins and membranes under low temperature (Rudolph and Crow, 1985); dehydration, stabilisation of double stranded helical structure of DNA (Rajendrakumar et al. 1997) and oxidative stress particularly by scavenging ROS (Takagi, 2008). Enhanced levels of proline under various abiotic and biotic stresses may be correlated with the stimulation of gene P5CS (Peng et al. 1996; Zhang et al. 1995). In transgenic tobacco ( Nicotiana tabacum), Kishor et al. (1995) demonstrated increase in proline levels due to over expression of p5cs gene responsible for encoding P5CS, a key enzyme in proline biosynthesis. References Alia A.S., Saradhi P.P., 1993. Suppression in mitochondrial electron transport is the prime cause behind stress induced proline accumulation. Biochemical and Biophysical Research Communications 193, 54–58. Aspinall D., Paleg L.G., 1981. Proline accumulation. Physiological aspects. In LG Paleg. D Aspinall, eds, The Physiology and Biochemistry of Drought Resistance in Plants. Academic Press, Sydney, pp 205-241 Bhandari and Nayyar, 2014. Hare P.D., Cress W.A., 1997. Metabolic implications of stress-induced proline accumulation in plants. Plant growth regulation 21, 79-10. Hoque M.A., Banu M.N., Okuma E., Amako K., Nakamura Y., Shimoishi Y., Murata Y., 2007. Exogenous proline and glycinebetaine increase NaClinduced ascorbate–glutathione cycle enzyme activities, and proline improve salt tolerance more than glycinebetaine in tobacco Bright Yellow-2 suspensioncultured cells. Journal of Plant, Physiology 164: 14571468.

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Islam M.M., Hoque M.A., Eiji O., Banu MNA., Yasuaki S., Yoshimasa N., Yoshiyuki M., 2009. Exogenous proline and glycinebetaine increase antioxidant enzyme activities and confer tolerance to cadmium stress in cultured tobacco cells. Journal of Plant Physiology 166: 1587-1597. Kishor P.B.K., Hong Z., Miao G.H., Hu CAA, Verma D.P.S., 1995. Overexpression of Δ1-pyrroline-5carboxylate synthetase increases proline production and confers osmotolerance in transgenic plants. Plant Physiology 108: 1387–1394. Matysik J., Alia Bhalu B., Mohanty P., 2002. Molecular mechanisms of quenching of reactive oxygen species by proline under stress in plants. Current Science 82, 5-10. Peng Z., Lu Q., Verma DPS., 1996. Reciprocal regulation of Δ1-pyrroline-5-carboxylate synthetase and proline dehydrogenase genes controls proline levels during and after osmotic stress in plants. Molecular and General Genetics 253, 334–341. Rajendrakumar C.S.V., Suryanarayana T., Reddy A.R., 1997. DNA helix destabilization by proline and betaine: possible role in the salinity tolerance process. FEBS Letters 410, 201–205. Rudolph A.S., Crowe J.H., 1985. Membrane stabilization during freezing: the role of two natural cryoprotectants, trehalose and proline. Cryobiology 22, 367–377. Srinivasan V., Balasubramaniam D., 1995. Proline is a proteicompatible hydrotope. Langmuir 11: 2830-2833. Takagi H., 2008. Proline as a stress protectant in yeast: physiological functions, metabolic regulations, and biotechnological applications. Applied Microbiology and Biotechnology 81, 211- 223. Van Swaaij C., Jacobsen E., Feensta W.J., 1985. Effect of cold hardening,wilting and exogenously applied proline on leaf proline content and frost tolerance of several genotypes of Solanum. Physiology Plantarum 64, 230–236. Yadeghari L.Z., Heidari R, Carapetian J., 2008. Influence of Cold Acclimation on Proline, Malondialdehyde (MDA), Total Proteins and Pigments Contents in Soybean (Glycine max) Seedlings. Research Journal of Biological Sciences 3: 74-79. Zhang CS, Liu Q, Verma DPS (1995) Removal of feedback inhibition of Δ1-pyrroline-5-carboxylate synthetase, a bifunctional enzymecatalyzing the first two steps of proline biosynthesis in plants. Journal of Biological Chemistry 270: 20491–20496.

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