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Regulation of Osmolytes Syntheses and Improvement of Abiotic Stress Tolerance in Plants
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Ambuj Bhushan Jha, Pallavi Sharma
Proline accumulation and its osmoprotective role under abiotic stresses have been reported in detail; however, not much has been discussed on the effect of regulatory molecules and signals on the expression of genes involved in proline’s biosynthetic pathway. In plants, the plastid and cytosol are the sites for proline biosynthesis, whereas degradation occurs in mitochondria (Ashraf and Foolad, 2007). Higher proline accumulation could be due to either activation of the biosynthetic pathway or inactivation of the degradation. In the proline biosynthetic process, pyrroline-5-carboxylate synthetase (P5CS) catalyzes the conversion of glutamate to glutamate semialdehyde (GSA), and GSA gets converted to pyrroline 5-carboxylate (P5C) by spontaneous cyclization (Kavi Kishor et al., 2005). P5C is reduced to proline by enzyme pyrroline-5-carboxylate reductase (P5CR). Alternatively, in plants, proline is also synthesized from arginine/ornithine (Adams and Frank, 1980; Bryan, 1990). The enzyme arginase converts arginine to ornithine. Ornithine is transaminated to P5C by orinithine-δ-aminotransferase (OAT) (Armengaud et al., 2004; Verbruggen and Hermans, 2008). Degradation of proline in mitochondria is catalyzed by the enzyme proline dehydrogenase or proline oxidase (PDH/PRODH), which converts proline to P5C, and then P5C dehydrogenase (P5CDH) produces glutamate from P5C (Joshi et al., 2010; Szabados and Savouré, 2010; Servet et al., 2012). P5CS is the rate-limiting enzyme for the biosynthesis, whereas PDH is the rate-limiting enzyme for the catabolism of proline (Ashraf and Foolad, 2007; Slama et al., 2015).
Regulatory role of folic acid in biomass production and physiological activities of Coriandrum sativum L. under irrigation regimes
Published in International Journal of Phytoremediation, 2022
Muhammad Tajammal Khan, Shakil Ahmed, Anis Ali Shah
Commonly, FA application nullifies the injuries of drought stress on plant development (Ibrahim et al. 2021). FA enhanced the proline production under water stress, which helps the plant to gain strength against turgor loss (Burguieres et al. 2007). Moreover, proline is an amino acid that could act as an osmolyte as well as molecular chaperons produced under the influence of the glutamate pathway during water deficit conditions. Whereas, FA (pteroylglutamic acid) naturally exhibits glutamic acid directly involved in the formation of glutamate. This reaction was catalyzed by two enzymes P5CS (pyrroline-5-carboxylate synthetase) and P5CR (pyrroline-5-carboxylate reductase) in plants for the synthesis of proline. The production of proline in cytosol diluted the cell and prevent plant tissue from dehydration (Sekhar et al. 2007; Shamsul et al. 2012). So, this connection demonstrated a significant role of FA in biochemical and physiological processes and the development of plants (Esfandiari et al. 2012).
Cadmium stress in plants: A critical review of the effects, mechanisms, and tolerance strategies
Published in Critical Reviews in Environmental Science and Technology, 2022
Taoufik El Rasafi, Abdallah Oukarroum, Abdelmajid Haddioui, Hocheol Song, Eilhann E. Kwon, Nanthi Bolan, Filip M. G. Tack, Abin Sebastian, M. N. V. Prasad, Jörg Rinklebe
Proline is a non-essential amino acid (Kumar et al., 2017) biosynthesized in chloroplasts and plant-cell cytoplasm (Szepesi & Szollosi, 2018; Verbruggen & Hermans, 2008) from an ornithine precursor and glutamate with the involvement of various genes such as ornithine-δ-aminotransferase, pyrroline-5-carboxylate reductase, and pyrroline-5-carboxylate synthetase (Kishor et al., 2015; Lehmann et al., 2010). It plays various roles during plant development, flowering, and seed development (Lehmann et al., 2010). Plants may synthetize proline in either the absence or presence of abiotic stress (e.g., metal exposure) (Kishor et al., 2015). It has been reported that in Cd exposure, proline content increases in different plant species, including Solanum nigrum (Sun et al., 2007), Arachis hypogaea (Dinakar et al., 2008), cucumber (Semida et al., 2018), bean (Rady et al., 2019), and hackberry (Celtis australis) (Hatamian et al., 2020). Proline is an important metabolite for plant adaptation, protection, and tolerance to Cd stress. Accumulation of proline in plants is recognized as a strategy to counteract Cd stress by adjusting osmotic potential, stabilization of membrane structures (Amari et al., 2017; Semida et al., 2018; Zouari et al., 2016), and reduction of oxidative stress (Rady et al., 2019; Singh, Pratap Singh et al., 2015). Olive plants (Olea europaea) exposed to Cd stress demonstrated an increase of proline content in both roots and leaves and increased Cd content in Cd-treated plants (Zouari et al., 2016). The latter authors demonstrated that application of exogenous proline leads to the increase of proline content, a notable decrease of Cd content in olive roots and leaves, and a decrease of oxidative stress indicators (H2O2, TBARS, and EL); however, an increase of gas exchange parameters, photosynthetic pigment content, and micronutrients (Ca, Mg, and K) was observed. Moreover, the protective role of proline includes formation of a nontoxic Cd-proline complex (Rehman et al., 2017; Sun et al., 2007), acting as a source of C and N, and activating the antioxidant system (Dinakar et al., 2008; Zouari et al., 2016).