Genotypic variation for water and salt stress induced proline dynamics in wheat
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Date
2016
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Punjab Agricultural University, Ludhiana
Abstract
The present study was conducted to evaluate the proline metabolism and its cross talk with various biochemical parameters in nineteen wheat genotypes viz. C 306, C 273, C 591, C 518, Type 11, Excalibar, Krichauff, Babax, Gladius, Drysdale, Kharchia, Krl 1-4, Krl 19, PBW 175, HD 2967, PBW 621, WH 1105, HD 3086 and PBW 660 raised under water deficit (8% PEG – 6000), water withholding and salt stress (300 mM NaCl) conditions. Enzymes involved in proline synthesis [glutamate dehydrogenase (GDH), pyrroline-5-carboxylate synthetase (P5CS) and δ-pyrroline-5-carboxylate reductase (P5CR)] and degradation [proline dehydrogenase (PDH)] were studied in the roots and shoots of seven day old seedlings. Based on various biochemical parameters, these genotypes were categorized into four groups i.e tolerant towards water stress (Excalibar, Krichauff, Babax, Drysdale, Gladius and C 306), tolerant towards salinity stress (Kharchia, Type 11, Krl 1-4 and Krl 19), intermediate tolerant (C 273, C 518 and C 591) and susceptible towards water and salinity stress (HD 2967, PBW 621, WH 1105, HD 3086, PBW 660 and PBW 175). Genotypes tolerant to water and salt stress revealed increased proline content and 1,1 diphenyl-picryl hydrazyl radical scavenging activity alongwith reduced content of thiobarbituric acid reactive species in parallel with decreased H2O2 content. Correspondingly, higher activities of GDH, P5CS and P5CR were also observed in these genotypes. However, the declining trend of PDH activity and low contents of TBARS and H2O2 were recorded in all studied genotypes except for HD 2967, PBW 621, HD 3086, PBW 175 and WH 1105. Results were further strengthened by studying the effect of ABA and its cross talk with various parameters under different stresses in selected five genotypes viz. Gladius, Drysdale, Kharchia, PBW 660 and PBW 175. Exogenous ABA application triggered the upregulation of proline synthesis in tolerant genotypes (Kharchia, Gladius and Drysdale) which indicated a predominant role of this osmolyte in maintaining root/shoot elongation and thereby, ameliorating the deleterious effect of ROS on membrane stability both under water and salt stress conditions. Overall, results indicated that increased proline content might have contributed in upregulating proline synthesizing enzymes and thereby overcoming oxidative stress more in tolerant genotypes than susceptible ones. In crux, results indicated that GDH activity was particularly responsible in proline synthesis pathway via enhancing P5CS activity and would trigger abiotic stress tolerance. Proline metabolizing enzymes particularly P5CS and GDH could be used as a marker for enhancing tolerance to these stresses by breeders and plant biotechnologists.
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Keywords
ABA, DPPH, H2O2, proline metabolism, water deficit, wheat seedlings, salt stress