Proline and its metabolism enzymes in cucumber cell cultures during acclimation to salinity

Abstract

Proline is an important osmolyte appearing as the result of salt stress response of plants. In the present study, we measured the proline concentration, activities of pyrroline-5-carboxylate synthetase (P5CS), pyrroline-5-carboxylate reductase (P5CR), and proline dehydrogenase (PDH) key regulatory enzymes in the biosynthesis and degradation of proline in the acclimated (AC20) and the non-acclimated (NAC) cucumber cell suspension cultures subjected to moderate (150 mM NaCl; AC20-150, NAC-150, respectively) and severe (200 mM NaCl; AC20-200, NAC-200, respectively) salt stress. The data showed that salt stress brought about a linear increase in proline content in both types of cultures. However, in the acclimated culture proline accumulation was observed earlier, in third hour after stress. Only in the acclimated culture moderate and severe stresses up-regulated P5CS activity throughout the experiment, whereas the activity of P5CR grew in response to both NaCl concentrations only in 24th and 48th hour. The severe salt stress resulted in decrease in P5CR in NAC-200 cultures. In response to salt stress, both types of cell suspension cultures reacted with decline in PDH activity below the spectrophotometrically detected level. Cell cultures vigor correlated with salt concentration and time of exposure to the stress factor. Both NaCl concentrations caused linear decline in vigor of the non-acclimated culture up to 80-90 % at the end of the experiment, whereas in the acclimated culture significant decrease by about 30-40 % was reached in 24th hour after stress. The presented data suggest that acclimation to salt stress up-regulated proline synthesis enzyme activity and caused intensive accumulations of proline by inhibiting its oxidation.

Growth and physiological adaptation of whole plants and cultured cells from a halophyte turf grass under salt stress

“…Proline accumulation is one of the most frequently reported modifications induced by salt and drought stress in plants, and is often considered to be involved in stress-tolerance mechanisms (Delauney and Verma 1993; Hare et al 1999), recovery from stress and stress signalling (Szabados and Savouré 2010). Proline might interact with enzymes to protect protein structure and activity against the consequences of dehydration-induced thermodynamic perturbation (Naliwajski and Skłodowska 2014). The proline concentrations in shoots of the Japanese genotype were higher than those in South African and Hawaiian genotypes in seawater salinity levels (Fig.…”

The Effects of Combined Abiotic and Pathogen Stress in Plants: Insights From Salinity and Pseudomonas syringae pv lachrymans Interaction in Cucumber

“…Salinity, affecting many agricultural areas of the globe, and plant pathogens represent an excellent example of abiotic and biotic stresses which co-occur in the field and their interaction may severely influence food quality and safety ( Munns and Gilliham, 2015 ). Salinity ( Naliwajski and Skłodowska, 2014 ; Forieri et al, 2016 ) and pathogenic bacteria ( Gao et al, 2013 ; Yang et al, 2015 ) were extensively studied as individual stresses, but their combined impact on crops is not well recognized, although evidence confirming their co-occurrence is still growing ( Dileo et al, 2010 ; Nostar et al, 2013 ; Nejat and Mantri, 2017 ; Zhang and Sonnewald, 2017 ). As to cucumber, the fourth most important vegetable crop worldwide ( Lv et al, 2012 ), 17% of the plants grown in salinated soils in Uzbekistan showed symptoms of Fusarium solani -induced diseases ( Egamberdieva et al, 2011 ), and increasing salinity of irrigation water from 0.01 to 5 dS m -1 increased the incidence of pythium damping-off of cucumber from 40 to 93% ( Al-Sadi et al, 2010 ).…”

Carbon Fluxes between Primary Metabolism and Phenolic Pathway in Plant Tissues under Stress

“…This evidence confirms the theoretical predictions that a trade-off exists between growth rate and defensive secondary metabolite investment when plant cells are in low-resource habitats [ 78 , 167 ]. Again, in order to understand the biochemical levels of regulatory mechanisms that control carbon fluxes between the primary and secondary metabolism, the role of proline, which figures prominently in most stress-mediated responses [ 115 , 168 , 169 ], has been also considered. The analysis of free proline content in cultivated artichoke cells shows an increase in proline level (by 38%–50% compared to the control) in response to nutritional stress.…”