Document Type : Original Article

Authors

1 MSc of Plant Physiology, Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran

2 Professor, Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran

3 Assistant Professor, Department of Biology, Faculty of Science, Payame Noor University, Tehran, Iran

Abstract

Introduction
The growth and production of crop plants are strongly affected by various environmental stress. Salinity stress affects all stages of plant development including germination, bud growth, vegetative growth, flowering, and fruiting. During the past few years, several genes that encoding various structural and regulatory proteins have been used to produce tolerant plants of abiotic stress. Tolerant plants have been selected by improving our knowledge about molecular mechanism of stress tolerance in plants. Plants increase organic osmolytes such as proline, glycine betaine, polyols, alcoholic sugars, and soluble sugars to modulate osmotic stress. The P5CS gene (proline-5-carboxylate-synthase) is a key enzyme in the pathway for proline synthesis and this amino acid increases resistance of plants to salinity. Although there are many reports about the key role of accumulation proline in mechanism of salinity tolerance, a little information is available about physiological and non-enzymatic antioxidant response of transgenic plants by P5Cs overexpression in salt stress. Therefore, the aim of this study was to evaluate physiological and non-enzymatic antioxidant responses of transgenic and non-transgenic tobacco to salinity under in vitro culture.
Materials and methods
In order to achieve this goal, transgenic and non-transgenic plants were selected by PCR experiment with NPTII: P5CS proprietary primers. Consequently, the expression of the P5CS gene in transgenic plants was significantly higher than non-transgenic plants. To investigate the mechanism of salt tolerance in tobacco, transgenic and non-transgenic tobacco plants were grown on MS medium containing 0, 100, 150, 200 mM NaCl. After 4 weeks of treatments, fresh and dry weight, photosynthetic pigments, sodium and potassium, proline, phenol, anthocyanin, flavonoid, ascorbate, and hydrogen peroxide were measured.
Results and discussion
Based on the results, dry and fresh weight as well as chlorophyll content in transgenic plants decreased less than non-transgenic plant under salt stress. For example, the fresh weight of non-transgenic plants in the medium with 100 and 200 mM NaCl decreased by 47% and 33% and their dry weight decreased by 23 and 33%, respectively compared with transgenic plants. Total chlorophyll content of transgenic plants in the medium with 100, 150 and 200 mM salt was improved by 25%, 22%, and 41% compared with non-transgenic plants, respectively. Also, the leaves of transgenic plants accumulated less sodium than non-transgenic plants in response to salinity stress. By adding 100, 150 and 200 mM salt to medium, the level of sodium in transgenic plants decreased by 50%, 17%, and 18% compared with non-transgenic plants respectively. Moreover, the level of phenolic, anthocyanin and flavonoid compounds in the transgenic plants were less than non-transgenic plants by adding salt to medium. The proline content of both transgenic and non-transgenic plants increased in response to salinity. In addition, there was a significant increase in proline content of transgenic plants compared to non-transgenic plant under salt stress. The ascorbate content in transgenic and non-transgenic plants did not change significantly in response to salinity. However, the hydrogen peroxide decreased significantly in transgenic plants as compared with non-transgenic plants in salt stress. The results showed that the accumulation of hydrogen peroxide in transgenic plants in the medium with 100, 150 and 200 mM salt was 83%, 41%, and 23% lower than non-transgenic plants, respectively. So, it seems that transgenic and non-transgenic tobacco plants were salt tolerant and salt sensitive respectively. It has been suggested that high proline content may lead to salt tolerance in plants. According to our experiment, overexpression of P5CS gene increased proline content in other plants and improved salinity resistance in transgenic plants.

Keywords

Abdel-Hameed, E.-S.S., 2009. Total phenolic contents and free radical scavenging activity of certain Egyptian Ficus species leaf samples. Food Chemistry. 114, 1271-1277.
Ahmad, P., Azooz, M., Prasad, M.N.V., 2013. Salt Stress in Plants: Signalling, Omics and Adaptations. Springer Science & Business Media.
Akhavan, Z., 2011, Study of P5CS gene expression and carbohydrate content changes in roots and leaves of transgenic tobacco plants (Nicotiana tabacum L.cv. Wisconsin) under in vitro salt stress condition. MSc dissertation, Faculty of Science Department of Biology, University of Isfahan, Iran.  [In Persian].
Armengaud, P., Thiery, L., Buhot, N., Grenier‐de March, G., Savouré, A., 2004. Transcriptional regulation of proline biosynthesis in Medicago truncatula reveals developmental and environmental specific features. Physiologia Plantarum. 120, 442-450.
Arnon, D.I., 1949. Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta vulgaris. Plant Physiology. 24, 1.
Ashraf, M.A., Ashraf, M., Ali, Q., 2010. Response of two genetically diverse wheat cultivars to salt stress at different growth stages: leaf lipid peroxidation and phenolic contents. Pakistan Journal of Botany. 42, 559-565.
Bates, L., Waldren, R., Teare, I., 1973. Rapid determination of free proline for water-stress studies. Plant and Soil. 39, 205- 207.
Bor, J.-Y., Chen, H.-Y., Yen, G.-C., 2006. Evaluation of antioxidant activity and inhibitory effect on nitric oxide production of some common vegetables. Journal Of Agricultural and Food Chemistry. 54, 1680-1686.
Chinnusamy, V., Jagendorf, A., Zhu, J.K., 2005. Understanding and improving salt tolerance in plants. Crop Science. 45, 437-448.
Chinnusamy, V., Zhu, J., Zhu, J.K., 2006. Salt Stress Signaling and Mechanisms of Plant Salt Tolerance, Genetic Engineering. Springer, pp. 141-177.
Chutipaijit, S., Cha-Um, S., Sompornpailin, K., 2009. Differential accumulations of proline and flavonoids in indica rice varieties against salinity. Pakistan Journal of Botany. 41, 2497-2506.
Delauney, A.J., Verma, D.P.S., 1993. Proline biosynthesis and osmoregulation in plants. The Plant Journal. 4, 215-223.
Dar, M.I., Naikoo, M.I., Rehman, F., Naushin, F., Khan, F.A., 2016. Proline accumulation in plants: roles in stress tolerance and plant development, in: Iqbal, N., Nazar, R.A., Khan, N. (eds.), Osmolytes and Plants Acclimation to Changing Environment: Emerging Omics Technologies. Springer India, New Delhi, pp. 155-166.
Ehsanpour, A., Fatahian, N., 2003. Effects of salt and proline on Medicago sativa callus. Plant Cell, Tissue and Organ Culture. 73, 53-56.
Ehsanpour, A., Twell, D., 2005. Analysis of SFL1 and SFL2 Promoter Regionin Arabidopsis thaliana using gateway cloning system. Journal of Science. 16, 303-309.
Ehsanpour, A.A., Zarei, S., Abbaspour, J., 2012. The role of over expression of P5CS gene on proline, catalase, ascorbate peroxidase activity and lipid peroxidation of transgenic tobacco (Nicotiana tabacum L.) plant under in vitro drought stress. Journal of Cell and Molecular Research. 4, 43-49.
Eryılmaz, F., 2006. The relationships between salt stress and anthocyanin content in higher plants. Biotechnology and Biotechnological Equipment. 20, 47-52.
Forghani, A.H., Almodares, A., Ehsanpour, A.A., 2018. Potential objectives for gibberellic acid and paclobutrazol under salt stress in sweet sorghum (Sorghum bicolor [L.] Moench cv. Sofra). Applied Biological Chemistry. 61, 113-124.
Forghani, A.H., Almodaress, A., Ehsanpour, A.A., 2017. Comparative effects of gibberellin and paclobutrazol on Na and k content, phenolic compounds and the activity of some enzymesin its biosynthesis pathway in sweet sorghum (sorghum bicolor) under salt stress. Journal of Crop Production and Processing. 7, 133-149. [In Persian with English summary].
Garratt, L.C., Janagoudar, B.S., Lowe, K.C., Anthony, P., Power, J.B., Davey, M.R., 2002. Salinity tolerance and antioxidant status in cotton cultures. Free Radical Biology and Medicine. 33, 502-511.
Gill, S.S., Tuteja, N., 2010. Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants. Plant Physiology and Biochemistry. 48, 909-930.
Hare, P., Cress, W., Van Staden, J., 1999. Proline synthesis and degradation: a model system for elucidating stress-related signal transduction. Journal of Experimental Botany. 50, 413-434.
Hasanuzzaman, M., Hossain, M.A., da Silva, J.A.T., Fujita, M., 2012. Plant response and tolerance to abiotic oxidative stress: antioxidant defense is a key factor.In: Venkateswarlu, B., Shanker, A., Shanker, C., Maheswari, M. (eds.),Crop Stress and its Management: Perspectives and Strategies. Springer, pp. 261-315.
Hasanuzzaman M., Nahar K., Fujita M., 2013. Plant response to salt stress and role of exogenous protectants to mitigate salt-induced damages. In: Ahmad, P., Azooz, M., Prasad, M. (eds.), Ecophysiology and Responses of Plants under Salt Stress. Springer, New York, NY. pp. 25-87.
Hernández, J.A., Ferrer, M.A., Jiménez, A., Barceló, A.R., Sevilla, F., 2001. Antioxidant systems and O2./H2O2 production in the apoplast of pea leaves. Its relation with salt-induced necrotic lesions in minor veins. Plant Physiology. 127, 817-831.
Hichem, H., Mounir, D., 2009. Differential responses of two maize (Zea mays L.) varieties to salt stress: changes on polyphenols composition of foliage and oxidative damages. Industrial Crops and Products. 30, 144-151.
Hu, C., Delauney, A.J., Verma, D., 1992. A bifunctional enzyme (delta 1-pyrroline-5-carboxylate synthetase) catalyzes the first two steps in proline biosynthesis in plants. Proceedings of the National Academy of Sciences. 89, 9354-9358.
Iqbal, N., Umar, S., Khan, N.A., Khan, M.I.R., 2014. A new perspective of phytohormones in salinity tolerance: regulation of proline metabolism. Environmental and Experimental Botany. 100, 34-42.
Iyer, S., Caplan, A., 1998. Products of proline catabolism can induce osmotically regulated genes in rice. Plant Physiology. 116, 203-211.
Khalid, K.A., da Silva, J.A.T., 2010. Yield, essential oil and pigment content of Calendula officinalis L. flower heads cultivated under salt stress conditions. Scientia Horticulturae. 126, 297-305.
Khan, N.A., Nazar, R., Iqbal, N., Anjum, N.A., 2012. Phytohormones and Abiotic Stress Tolerance in Plants. Springer-Verlag Berlin Heidelberg, Germany.
Kishor, P.K., Sangam, S., Amrutha, R., Laxmi, P.S., Naidu, K., Rao, K., Rao, S., Reddy, K., Theriappan, P., Sreenivasulu, N., 2005. Regulation of proline biosynthesis, degradation, uptake and transport in higher plants: its implications in plant growth and abiotic stress tolerance. Current Science. 424-438.
Lutts, S., Kinet, J., Bouharmont, J., 1996. Effects of various salts and of mannitol on ion and proline accumulation in relation to osmotic adjustment in rice (Oryza sativa L.) callus cultures. Journal of Plant Physiology. 149, 186-195.
Maggio, A., Miyazaki, S., Veronese, P., Fujita, T., Ibeas, J.I., Damsz, B., Narasimhan, M.L., Hasegawa, P.M., Joly, R.J., Bressan, R.A., 2002. Does proline accumulation play an active role in stress‐induced growth reduction? The Plant Journal. 31, 699-712.
Makkar, H.P., Siddhuraju, P., Becker, K., 2007. Plant Secondary Metabolites. Humana Press.
Mani, S., Van de Cotte, B., Van Montagu, M., Verbruggen, N., 2002. Altered levels of proline dehydrogenase cause hypersensitivity to proline and its analogs in Arabidopsis. Plant Physiology. 128, 73-83.
Mittova, V., Tal, M., Volokita, M., Guy, M., 2002. Salt stress induces up‐regulation of an efficient chloroplast antioxidant system in the salt‐tolerant wild tomato species Lycopersicon pennellii but not in the cultivated species. Physiologia Plantarum. 115, 393-400.
Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bio assays with tobacco tissue cultures. Physiologia Plantarum. 15, 473-497.
Nanjo, T., Kobayashi, M., Yoshiba, Y., Kakubari, Y., Yamaguchi-Shinozaki, K., Shinozaki, K., 1999. Antisense suppression of proline degradation improves tolerance to freezing and salinity in Arabidopsis thaliana. Febs Letters. 461, 205-210.
Nap, J.-P., Bijvoet, J., Stiekema, W.J., 1992. Biosafety of kanamycin-resistant transgenic plants. Transgenic Research. 1, 239-249.
Peng, Z., Lu, Q., Verma, D., 1996. Reciprocal regulation of Δ 1-pyrroline-5-carboxylate synthetase and proline dehydrogenase genes controls proline levels during and after osmotic stress in plants. Molecular and General Genetics, MGG. 253, 334-341.
Per, T.S., Khan, N.A., Reddy, P.S., Masood, A., Hasanuzzaman, M., Khan, M.I.R., Anjum, N.A., 2017. Approaches in modulating proline metabolism in plants for salt and drought stress tolerance: Phytohormones, mineral nutrients and transgenics. Plant Physiology and Biochemistry. 115,126-140.
Poljakoff‐Mayber, A., Somers, G., Werker, E., Gallagher, J., 1994. Seeds of Kosteletzkya virginica (Malvaceae): their structure, germination, and salt tolerance. II. Germination and salt tolerance. American Journal of Botany. 81, 54-59.
Razavizadeh, R., Ehsanpour, A., 2009. Effects of salt stress on proline content, expression of delta-1-pyrroline-5-carboxylate synthetase, and activities of catalase and ascorbate peroxidase in transgenic tobacco plants. Biological Letters. 46, 63-75.
Razavizadeh, R., 2010, Evaluation of P5CS gene over expression on some physiological parameters and proteomics of transgenic tobacco plants under in vitro salt stress. PhD dissertation, Faculty of Science Department of Biology, University of Isfahan, Iran.  [In Persian].
Riahi, M., Ehsanpour, A.A., 2013. Responses of transgenic tobacco (Nicotiana plambaginifolia) over-expressing P5CS gene underin vitrosalt stress. Progress in Biological Sciences. 2, 76-84.
Sairam, R., Tyagi, A., 2004. Physiological and molecular biology of salinity stress tolerance in deficient and cultivated genotypes of chickpea. Plant Growth Regulation. 57, 109-114.
Santos, C.V., 2004. Regulation of chlorophyll biosynthesis and degradation by salt stress in sunflower leaves. Scientia Horticulturae. 103, 93-99.
Santos, M., Camara, T., Rodriguez, P., Claparols, I., Torne, J., 1996. Influence of exogenous proline on embryogenic and organogenic maize callus subjected to salt stress. Plant Cell, Tissue and Organ Culture.59-65,47.
Shi, G., Liu, C., Cui, M., Ma, Y., Cai, Q., 2012. Cadmium tolerance and bioaccumulation of 18 hemp accessions. Applied Biochemistry and Biotechnology. 168, 163-173.
Soussi, M., Ocana, A., Lluch, C., 1998. Effects of salt stress on growth, photosynthesis and nitrogen fixation in chick-pea (Cicer arietinum L.). Journal of Experimental Botany. 49, 1329-1337.
Steward, G.R., Larher F.,1980. Accumulation of amino acids and related compounds in relation to environmental stress. Amino acids and derivatives. In: Paul, K.S., Eric, E.C. (eds.), Biochemistry of Plants. 1sted. Volume 5. Academic Press; New York, NY, USA. pp. 609–635
Stewart, G., Lee, J., 1974. The role of proline accumulation in halophytes. Planta. 120, 279-289.
Thompson, J.F., 1980. Arginine synthesis, proline synthesis, and related processes, Amino acids and derivatives. Elsevier, pp. 375-402.
Thompson, M.R., Douglas, T.J., Obata‐Sasamoto, H., Thorpe, T.A., 1986. Mannitol metabolism in cultured plant cells. Physiologia Plantarum. 67, 365-369.
Tiwari, J.K., Munshi, A.D., Kumar, R., Pandey, R.N., Arora, A., Bhat, J.S., Sureja, A.K., 2010. Effect of salt stress on cucumber: Na+/K+ ratio, osmolyte concentration, phenols and chlorophyll content. Acta Physiologiae Plantarum. 32, 103-114.
Trotel‐Aziz, P., Niogret, M.F., Larher, F., 2000. Proline level is partly under the control of abscisic acid incanola leaf discs during recovery from hyper‐osmotic stress. Physiologia Plantarum. 110, 376-383.
Van Rensburg, L., Krüger, G., Krüger, H., 1993. Proline accumulation as drought-tolerance selection criterion: its relationship to membrane integrity and chloroplast ultrastructure in Nicotiana tabacum L. Journal of Plant Physiology. 141, 188-194.
Velikova, V., Yordanov, I., Edreva, A., 2000. Oxidative stress and some antioxidant systems in acid rain-treated bean plants: protective role of exogenous polyamines. Plant Science. 151, 59-66.
Venekamp, J., 1989. Regulation of cytosol acidity in plants under conditions of drought. Physiologia Plantarum. 76, 112-117.
Verma, S., Mishra, S.N., 2005. Putrescine alleviation of growth in salt stressed Brassica juncea by inducing antioxidative defense system. Journal of Plant Physiology. 162, 669-677.
Wagner, G.J., 1979. Content and vacuole/extravacuole distribution of neutral sugars, free amino acids, and anthocyanin in protoplasts. Plant Physiology. 64, 88-93.
Wahid, A., Ghazanfar, A., 2006. Possible involvement of some secondary metabolites in salt tolerance of sugarcane. Journal of Plant Physiology.163, 723-730.
Yancey, P.H., 2001. Water stress, osmolytes and proteins. American Zoologist 41, 699-709.
Yoshiba, Y., Kiyosue, T., Nakashima, K., Yamaguchi-Shinozaki, K., Shinozaki, K., 1997. Regulation of levels of proline as an osmolyte in plants under water stress. Plant and Cell Physiology. 38, 1095-1102.
Zhu, J.-K., 2000. Genetic analysis of plant salt tolerance using Arabidopsis. Plant Physiology. 124, 941-948.