Volume 3 • Issue 6 • 1000e170 Biochem Pharmacol ISSN:2167-0501 BCPC, an open access journal Editorial Open Access Biochemistry & Pharmacology: Open Access Singh et al., Biochem Pharmacol 2014, 3:6 http://dx.doi.org/10.4172/2167-0501.1000e170 Proline and Salinity Tolerance in Plants Madhulika Singh 1 , Jitendra Kumar 1 , Vijay Pratap Singh 2* and Sheo Mohan Prasad 1* 1 Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Allahabad-211 002, India 2 Govt. Ramanuj Pratap Singhdev Post Gradute College, Baikunthpur, Koriya-497335, Chhattisgarh, India *Corresponding author: Sheo Mohan Prasad, Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Allahabad-211 002, India, Tel: +919450609911; E-mail: profsmprasad@gmail.com Vijay Pratap Singh, Govt. Ramanuj Pratap Singhdev Post Graduate College, Baikunthpur, Korea-497335, Chhattisgarh, India, Tel: +919451373143; E-mail: vijaypratap.au@gmail.com Received: September 29, 2014; Accepted: September 06, 2014; Published September 08, 2014 Citation: Singh M, Kumar J, Singh VP, Prasad SM (2014) Proline and Salinity Tolerance in Plants. Biochem Pharmacol 3: e170. doi:10.4172/2167-0501.1000e170 Copyright: © 2014 Singh M et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. he ever-increasing populations in developing countries like India adversely afecting the agro-ecosystem, due to unsustainable agricultural practices. he problem of salinity is of global concern but it is more conspicuous in arid and semi-arid regions of the world, which are characterized by limited rainfall, high transpiration, and high temperature [1]. Salinity afects almost every aspect of the physiology and biochemistry of plants and signiicantly reduces their yield [2]. Salt stress causes an imbalance of cellular ions resulting in ion toxicity (primary efect), and osmotic stress (secondary efect) while high salinity induces the production of severe toxic oxygen derivatives (ROS) such as superoxide radicals (O 2 ˙ˉ), singlet oxygen ( 1 O 2 ), hydrogen peroxide (H 2 O 2 ) and consequently formation of the most toxic hydroxyl radicals ( • OH) through fenton reaction in plants, and may interact with many essential macromolecules and metabolites causing cellular damage [3,4]. In order to protect cells and tissue from oxidative damage, plants must produce low molecular weight non-enzymatic antioxidants such as proline, glutathione and ascorbate as well as enzymatic antioxidants including peroxidase, superoxide dismutase, ascorbate peroxidase and catalase to defend against oxidative stress [3,4]. One of the eicient protection mechanisms of plant against hyperosmotic stress is the increasing endogenous level of compatible solutes such as proline, ectoine, glycine betaine and sorbitol [3]. In many plants, free proline accumulates in response to the imposition of a wide range of biotic and abiotic stresses. Most attempts have been taken into consideration on the ability of proline to mediate osmotic adjustment, stabilise subcellular structures and scavenge toxic oxygen derivatives. High levels of proline synthesized during stress conditions and also maintain the NAD(P)+/NAD(P)H ratio [5]. Proline is multifunctional amino acids and also a signalling molecule acting as a plant growth regulator by triggering cascade signalling processes [6]. Proline preferred as a common osmolyte in plants and get up-regulated against diferent stresses [4,7]. Its accumulation in plants provides protection against salinity and drought stress. Exogenous application of proline improves the crop tolerance against various abiotic stresses particularly salinity by protecting them from the severe efects of ROS [7]. Plants tend to enhance its endogenous level with continuously increasing levels of salinity [8]. his editorial focused on adverse impact of NaCl stress on plants, and how plants survive under salt afected land by increasing their endogenous level of proline. he biosynthesis and degradation of proline, and its accumulation in plants is regulated by diferent abiotic stresses and salinity has the great concern [6]. Proline synthesis in plants consists two diferent cycles. First of them is glutamate cycle, in which, glutamate is phosphorylated to ϒ-glutamyl phosphate and reduced to glutamate-ϒ- semialdehyde (GSA), which is spontaneously cyclized to ∆ 1 -pyrroline- 5-carboxylate (P5C). he second is the ornithine cycle, in which ornithine is transaminated to GSA by ornithine ϒ-aminotransferase (OAT) [6]. Proline biosynthesis from glutamate consist two enzyme reactions involving ∆ 1 -pyrroline-5-carboxylate synthetase (P5CS) and glutamate dehydrogenase (GDH). On the other hand, the proline accumulation depends on its degradation rate, which is catalysed by the mitochondrial enzyme proline dehydrogenase (PDH) [6]. In plants, both PDH and ∆ 1 -pyrroline-5-carboxylate dehydrogenase (P5CDH) are attached to the matrix side of the inner mitochondrial membrane [5]. Proline synthesis initiates the generation of NADP + , which acts as the backbone for ribose 5-phosphate required for the purines synthesis, and proline oxidation yields the reduced electron carriers, which provide energy for the numbers of biochemical reaction such as nitrogen ixation [9]. Exogenous application of proline may be a good approach to decrease the undesirable efects of salinity stress on plants [6,10] and metal stress [11]. It was also reported that, the exogenous application of proline alleviates the adverse efects of salt by reducing the accumulation of Na + and Cl − in plants [10]. Proline provides tolerance against diferent abiotic stresses by increasing their endogenous level and their intermediate enzymes in plants. It was also reported that, the exogenous application of proline increases the endogenous level of proline in bean (Phaseolus vulgaris L.) [11]. Proline regulates expression of number of genes related to antioxidant enzymes under salt stress. Among diferent genes, one of the gene ∆ 1 -pyrroline-5-carboxylate synthetase is responsible for up-regulating the stress-induced proline accumulation under salinity stress [9]. Finally, salt stress imposed the severe efects on plant growth and productivity by interrupting the normal metabolic processes and the proline may alleviate the negative impact of salt by decreasing osmotic stress that consequently maintain the membrane integrity and its function. he exogenous application of proline could ofer a simple and an economical approach for farmers to reduce the crop loss risk in salt contaminated land. However, further studies are needed at physiological and molecular levels to gain deeper insight in understanding interaction of NaCl induced oxidative stress and alleviation mechanism of exogenous proline in crops. Acknowledgement Authors are thankful University Grants Commission, New Delhi for inancial assistance. One of the authors Jitendra Kumar is also thankful to University Grants Commission, New Delhi for providing inancial support as JRF under Rajiv Gandhi National Fellowship.