Changes In Proline Content Research Articles

Physiological response of diverse maize genotypes to heat stress and simple sequence repeats markers-based genotyping in Rawalpindi, Punjab Pakistan

The current study was designed to observe the response of maize genotypes under high-temperature stress conditions and to check their diversity using simple sequence repeats (SSR) markers in in-vitro conditions. Maize genotypes (n=10) were subjected to heat stress at ~45 °C for 72 h after growing into young seedlings. Their physiological responses were determined by measuring the changes in proline content (PC), chlorophyll content (CC), cell membrane stability (CMS), relative water content (RWC) and osmotic potential (Ψπ). The analysed data disclosed significant differences (P ≤ 0.01) among all the characters. Comparison between control and heat-treated genotypes depicted a notable increase in PC, Ψπ while a decrease in CC, RWC and CMS index in heat-treated plants. Maize genotypes viz. NCEV-1230, NARC-4, HN Gold and OPV-20 performed better under heat stress and also showed a strong genetic relationship for similarity index in dendrogram based on selected SSR markers related to abiotic stress tolerance. This study is beneficial for understanding the physiological behaviour of maize plants under heat stress and for further genetic studies on maize to select heat-tolerant lines for breeding programs

Assessment of ammonium fertilization as a stimulus for proline accumulation in Oryza sativa L. during cyanide assimilation

The interactions between ammonium fertilization, cyanide (KCN) assimilation and proline accumulation in rice seedlings (Oryza sativa L. cv. XZX 45) were investigated during the current investigation. Results indicated that rice seedlings possess effective assimilation potential for exogenous CN− after 2-d exposure, where increases in the assimilation rates of CN− were negatively correlated with ammonium fertilization. During ammonium starvation, negligible change in proline content was detected in both rice tissue samples subjected to CN− exposure, suggesting that the degradation products of CN− by rice seedlings might not serve as nitrogen donors for proline synthesis. In the absence of exogenous CN−, proline accumulation in shoots was evident with enhancing ammonium fertilization, whereas marginal changes of proline content were observed in roots. Results also indicated that the addition of exogenous CN− significantly decreased proline content in shoots of rice seedlings fed with ammonium at the concentrations of 19.75–59.25 mg N/L. In conclusion, both the supplied ammonium and CN− were quickly assimilated into other nitrogen-containing compounds in rice seedlings through a nitrogen nutrient pathway; the contribution of nitrogen from ammonium assimilation into proline synthesis was evident in shoots after 2-d exposure, but it was repressed by exogenous CN−.

Fatty Acid Profiling of Polyethylene Glycol Adapted and Un-Adapted Cell Lines of <i>Oryza sativa</i> L.cv. Swat-1 under Temperature Stress

Higher plants can adapt to abiotic stress to a certain degree. In this study, the impact of temperature stress on osmotic stress adapted and un-adapted cell lines of rice (Oryza sativa L.cv Swat-1) was observed. For the change in proline content, relative growth rate, saturated and unsaturated fatty acid were evaluated. The cell lines were incrementally adapted to 20% polyethylene glycol. The adapted lines showed significantly higher growth rate and proline content as compared to the un-adapted cell lines on temperature stress. Among saturated fatty acids palmitic acid (C16:0), stearic acid (C18:0) and myristic acid (C14:0) were the prominent fatty acids detected while among unsaturated fatty acid Oleic acid (C18:1c) and Linoleic acid (C18:2c) were the major fatty acids found. Under low temperature stress the percentage of saturated fatty acids was found to be lower (53%) in adapted cell line as compared to the un-adapted cell line (63%) while the percentage of saturation increased (83%) in adapted line under high temperature stress as compared to un-adapted line (70%). On the other hand at low temperature stress the percent level of unsaturated fatty acids in the adapted line was higher (48%) than the un-adapted cell line (37%). In conclusion, adaptation to one abiotic stress confers co-tolerance to the other abiotic stresses. Fatty acids saturation level could be a crucial factor in the plant ability to tolerate heat and cold stress.

Physiological, micro-morphological and metabolomic analysis of grapevine (Vitis vinifera L.) leaf of plants under water stress

Grapes are one of the most important fruits because of their economic and nutritional benefits, and grapevines are widely cultivated in arid and semi-arid areas. Therefore, it is critical to study the mechanism by which grapevines respond to water stress. In this research, micro-morphological and metabolomic analyses were conducted to evaluate the effects of water stress on stomatal morphology and volatile compounds extracted from the leaves of grapevine plants. There were two treatments: well-watered plants (watered daily) and drought-stressed plants (no irrigation). Plant weights were recorded, and the well-watered plants were irrigated daily to replace the water lost to evapotranspiration. The water status of the grapevines was determined according to their relative water content. The changes in proline content, hydrogen peroxide content, lipid peroxidation and antioxidant activities, as well as those of photosynthetic parameters and chlorophyll fluorescence, were monitored as markers of water stress. The microscopic changes in stomatal behavior were observed using a scanning electron microscope. A total of 12 secondary volatile compounds, including aldehydes, ketones and alcohols, were detected in the grapevine leaves. Among them, (E)-2-hexenal and 3-hexenal showed a significant increase after water stress. Multivariate statistical analysis revealed that the levels of 3-hexenal and (E)-2-hexenal were closely related to the changes in proline, hydrogen peroxide (H2O2), malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD). These results suggested that water stress could regulate the accumulation of green leaf volatiles, especially (E)-2-hexenal and 3-hexenal, in coordination with the reactive oxygen species (ROS) scavenging system. These compounds may act as signaling compounds in response to water stress in grapevines.

Biochemical differences underlie varying drought tolerance in four Festuca arundinacea Schreb. genotypes subjected to short water scarcity

Festuca arundinacea Schreb. (tall fescue) is a turfgrass desired for planting in transition-zones. To determine the major processes associated with drought tolerance in this crop, four cultivars were analyzed for enzymatic and non-enzymatic antioxidant activity as well as SGR transcript level under drought stress. These cultivars were selected from larger set of eleven tall fescue cultivars based on genetic relationships delineated via inter-simple sequence repeat (ISSR) analysis. This analysis divided the cultivars into 6 groups, according to Jaccard’s similarity coefficient (65 %), and identified Jaguar, h–d, Pixie, and Mini-mustang as representing diversity within the samples. These cultivars were thus subjected to drought stress treatment by withholding irrigation for up to 8 days. By the end of the treatment, two of the four cultivars had decreased chlorophyll content; Jaguar and h–d, moderately drought-tolerant cultivars did not display significant differences. Notably, the FaSGR transcript increased drastically over the course of the drought stress in Pixie and Mini-Mustang, in contrast to Jaguar and h–d, supporting the notion of SGR-mediated chlorophyll degradation in the less drought-tolerant cultivars. Biochemical adaptation to drought stress includes accumulation of solutes such as proline to maintain turgor, and detoxification of drought-associated reactive oxygen species. Pixie, Jaguar, and Mini-mustang exhibited drastic changes in proline content as compared to h–d, possibly due to their dependency on proline in order to maintain cellular homeostasis against drought stress. The drought-tolerant h–d may accumulate only slightly more proline due to other drought-tolerance adaptations. Water scarcity during drought stress significantly increased superoxide dismutase (SOD) and ascorbate peroxidase (APX) activity in all cultivars, though the extent of induction was correlated with drought susceptibility. This suggests that most of the superoxide that was produced as a result of drought stress was converted to H2O2 by SOD and subsequently detoxified by APX into H2O. Collectively, these data indicate that the cultivars Pixie and Mini-mustang protect critical cellular enzymes and structures during severe drought stress through drastically increased proline and SOD activity, while the more drought-tolerant h–d and jaguar do not require such extreme biochemical modifications.

Changes in Proline and Polyphenol oxidase enzyme activity in some Banana Cultivars and Hybrids under water stress

Plant growth and productivity is adversely affected by abiotic stresses induced changes in proline content and polyphenol oxidase enzyme activity. Field experiments were conducted at the National Research Centre for banana, Thiruchirapalli, during the growing season of 2011-2013 to compare the changes in proline content and PPO enzyme activity in twelve main crop and ratoon crop ofbanana cultivars and hybrids in 5 th and 7 th MAP (Month after Planting) under t wo levels of irrigation. The lowest reduction in the bunch yield of tolerant banana cultivars and hybrids viz., Karpuravalli, Karpuravalli x PisangJajee, Saba, and Sannachenkathali with the highest increase in proline and PPO enzyme activity was observed in 5 th and 7 th MAP stage due to 50 per cent depletion in available soil moisture (ASM) of the stress.

RENDIMIENTO Y ABSORCIÓN DE ALGUNOS NUTRIMENTOS EN PLANTAS DE CAMOTE CULTIVADAS CON ESTRÉS HÍDRICO Y SALINO

Sweet potato (Ipomoea batatas L.) is a low production cost crop that is grown during almost the whole year, mainly in developing countries. In arid and semiarid regions, the presence of salinity and water stress can generate yield reductions and losses in the quality of the tuber roots. To address these issues, an experiment was performed to determine yield, N, P, K, Ca, Mg and Na uptake and proline content in plants belonging to two sweet potato cultivars with a different degree of salt tolerance, grown under three (0, 8 and 14 mmol NaCl) salt and two watering regimes (watering after two and four days), during summer-fall conditions of 2009. Salinity and watering frequencies were controlled by using the soilless culture technique. Both water and salt stresses reduced tuber root yields. The yield reduction is explained by a reduction in the uptake of N, P, K, Ca and Mg with the water stress treatment, and an increased Na uptake in the high salinity treatment. The salt and water stress adjustments were reflected in an increment in proline content in leaves and tuber roots. The results confirm the tolerant cultivar as a hardy variety adaptable to abiotic stresses, whereas the non-tolerant variety had lower yield and nutrient uptake. The results did not support the hypothesis that changes in proline content might be used as fast screening tools to discriminate between tolerant and susceptible sweet potato cultivars.

Evaluation of Some Biochemical Responses in Resistance of Fifteen Bread Wheat (Triticum aestivum L.) Genotypes to Wheat streak mosaic virus

Two greenhouse experiments were conducted in 2008-2010 at College of Agriculture, Shiraz University, Iran to evaluate the effectiveness of changes in protein content, peroxidase activity, phenolic compounds, free amino acids content and proline in response to wheat streak mosaic virus (WSMV) infection, in screening resistant bread wheat ( Triticum aestivum L.) genotypes. Fifteen wheat genotypes consisting of WSMV tolerant, intermediate and susceptible genotypes were grown in two randomized complete designs with three replications. The experiments only differed with respect to their inoculation (either infected or non-infected). The results indicated that viral infection increased the total protein and peroxidase activity of leaves in tolerant genotypes but viral infection decreased them in susceptible genotypes. Phenolic compounds increased in all infected genotypes but these increases are the highest in tolerant genotypes as compared to intermediate and susceptible ones. Viral infection reduced free amino acids in genotypes in general. The changes in proline content did not show a typical trend in tolerant, intermediate or susceptible genotypes. The analysis of variance indicated that the linear regression of leaf damage rating on the changes in total protein, peroxidase activity and phenols in the leaf was significant but the linear regression of leaf damage rating on the changes in free amino acids and proline in the leaf was not significant. Our results demonstrate the changes in total protein, peroxidase activity and phenolic compounds in a genotype could be used as suitable biochemical markers for assessing the WSMV tolerant wheat plants when grown under infected condition.

Assessment of the influence of different sample processing and cold storage duration on plant free proline content analyses

A method which is widely accepted for the analysis of free proline content in plant tissues is based on the use of 3% sulfosalicylic acid as an extractant, followed by spectrophotometric quantification of a proline-ninhydrin complex in toluene. However, sample preparation and storage may influence the proline actually measured. This may give misleading or difficult to compare data. To evaluate free proline levels fresh and frozen strawberry (Fragaria × ananassa Duch.) leaves and soybean [Glycine max (L.) Merr.] hypocotyl tissues were used. These were ground with or without liquid nitrogen and proline extracted with sulfosalicylic acid. A particular focus was the influence of plant sample cold storage duration (1, 4 and 12 weeks at -20°C) on tissue proline levels measured. The free proline content analyses, carried out in leaves of Fragaria × ananassa Duch. as well as in hypocotyls of Glycine max (L.) Merr., showed a significant influence of the sample preparation method and cold storage period. Long-term storage of up to 12 weeks at -20°C led to a significant increase in the measured proline in all samples analysed. The observed changes in proline content in plant tissue samples stored at -20°C indicate the likelihood of the over-estimation of the proline content if the proline analyses are delayed. Plant sample processing and cold storage duration seem to have an important influence on results of proline analyses. Therefore it is recommended that samples should be ground fresh and analysed immediately.

Changes of Proline Content and Activity of Antioxidative Enzymes in Two Canola Genotype under Drought Stress

Changes of Proline Content and Activity of Antioxidative Enzymes in Two Canola Genotype under Drought Stress

Quantification of free and conjugated abscisic acid in five genotypes of barley ( Hordeum vulgare L.) under water stress conditions

The goal of the present study was to obtain new insights into the mechanisms underlying drought stress adaptations in barley plants. For this purpose we evaluated changes in endogenous abscisic acid (ABA) and its glucose ester conjugate (ABAGE), as well as changes in proline content, water relations and growth parameters of five barley genotypes with different drought resistance characteristics. Different responses among the five genotypes studied (Ardahoui, Pakistan, Rihane, Manel ad Roho) led to changes in their pattern of growth and development under drought conditions. Water stress induced a reduction in relative water content, as well as an increase in proline content and endogenous ABA concentrations in all tested genotypes. The lack of water led to a 2-fold increase in proline content for var. Rihane and to a 5-fold increase in endogenous ABA for cv. Ardhaoui. Also, increases in endogenous ABAGE in all genotypes except for cv. Ardhaoui were observed. Our results show that changes in ABA and ABAGE correlated with variations in proline content and growth parameters of these genotypes which present different mechanisms to cope with water stress. We also suggest that new regulatory mechanisms implying ABA mobilization can be of great importance in adaptation of barley to drought.

Changes of Proline Content, Activity, and Active Isoforms of Antioxidative Enzymes in Two Alfalfa Cultivars Under Salt Stress

The plants of two alfalfa ( Medicago sativa L.) cultivars differing in salt tolerance were subjected to three salt treatments, 70, 140, and 210 mM NaCl for 7 days. Root, shoot, and leaf growths were inhibited by increased salt treatments in both cultivars, and at 140 and 210 mM salt treatments, Zhongmu 1 had significantly higher root, shoot, and leaf dry weights per plant than Defi. The malondialdehyde (MDA) accumulation in Defi was considerably greater than in Zhongmu 1, indicating a higher degree of lipid peroxidation at 140 and 210 mM salt treatments. The changes in the activity and active isoforms of antioxidant enzymes such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), and ascorbate peroxidase (APOX, EC 1.11.1.11), accumulation of free proline, and rate of lipid peroxidation in leaves of two alfalfa cultivars were also investigated. After stress, the activity and active isoforms of antioxidative enzymes were altered and the extent of alteration varied between the cultivar Defi and Zhongmu 1. The proline accumulation in Defi was considerably greater than in Zhongmu 1 at 210 mM salt treatment. This indicated that proline accumulation may be the result, instead of the cause, of salt tolerance.

Photosynthetic, Physiological and Biochemical Responses of Tomato Plants to Polyethylene Glycol‐Induced Water Deficit

Abstract: Polyethylene glycol (PEG 6000)‐induced water deficit causes physiological as well as biochemical changes in plants. The present study reports on the results of such changes in hydroponically grown tomato plants (Ly coper sicon esculentum Mill. cv. Nikita). Plants were subjected to moderate and severe levels of water stress (i.e. water potentials in the nutrient solution of‐0.51 and‐1.22 MPa, respectively). Water stress markedly affected the parameters of gas exchange. Net photosynthetic rate (Pn) decreased with the induction of water stress. Accordingly, a decrease in the transpiration rate (E) was observed. The ratio of both (Pn/E) resulted in a decrease in water use efficiency. One of the possible reasons for the reduction in Pn is structural damage to the thylakoids, which affects the photosynthetic transport of electrons. This was indicated by an increase in non‐photochemical quenching and a reduction in the quantum yield of photosystem II. Furthermore, a decrease in both leaf water potential and leaf osmotic potential was observed, which resulted in a significant osmotic adjustment during stress conditions. Analysis of the physiological responses was complemented with a study on changes in proline content. In stressed plants, a 10‐fold increase in proline content was detected compared with control plants. It is clear that water stress tolerance is the result of a cumulative action of various physiological and biochemical processes, all of which were affected by PEG 6000‐induced water stress.(Managing editor: Ping HE)

Proline accumulation and glutamine synthetase activity are increased by salt-induced proteolysis in cashew leaves

In this study cashew (Anacardium occidentale) plants were exposed to a short- and long-term exposure to NaCl in order to establish the importance of the salt-induced proteolysis and the glutamine synthetase activity on the proline accumulation. The cashew leaf showed a prominent proline accumulation in response to salt stress. In contrast, the root tissue had no significant changes in proline content even after the drastic injury caused by salinity on the whole plant. The leaf proline accumulation was correlated to protease activity, accumulation of free amino acid and ammonia, and decrease of both total protein and chlorophyll contents. The leaf GS activity was increased by the salt stress whereas in the roots it was slightly lowered. Although the several amino acids in the soluble pool of leaf tissue have showed an intense increment in its concentrations in the salt-treated plants, proline was the unique to show a proportional increment from 50 to 100 mol m-3 NaCl exposure (16.37 to 34.35 mmol kg-1 DM, respectively). Although the leaf glutamate concentration increased in the leaves of the salt-stressed cashew plants, as compared to control, its relative contribution to the total amino acid decreased significantly in stressed leaves when compared to other amino acids. In addition, when the leaf discs were incubated with NaCl in the presence of exogenous precursors (Glu, Gln, Orn or Arg) involved in the proline synthesis pathways, the glutamate was unique in inducing a significant enhancement of the proline accumulation compared to those discs with precursor in the absence of NaCl. These results, together with the salt-induced increase in the GS activity, suggest an increase in the de novo synthesis of proline probably associated with the increase of the concentration of glutamate. Moreover, the prominent salt-induced proline accumulation in the leaves was associated with the higher salt-sensitivity in terms of proteolysis and salt-induced senescence as compared to the roots. In conclusion, the leaf-proline accumulation was due, at least in part, to the increase in the salt-induced proteolysis associated with the increments in the GS activity and hence the increase in the concentration of glutamate precursor in the soluble amino acid pool.

Hg and Cd Induced Changes in Proline Content and Activities of Proline Biosynthesizing Enzymes in Phaseolus Aureus and Triticum Aestivum

The effect of mercury and cadmium, in the form of HgCl2 and CdCl2 respectively, on proline accumulation and two key proline biosynthesizing enzymes, Δ1-pyrroline-5-carboxylate synthetase (P5CS) and Δ1-pyrroline-5-carboxylate reductase (P5CR), was investigated in Phaseolus aureus Roxb. and Triticum aestivum L. The 5-d-old seedlings were exposed to 0.05, 0.1, 0.2 or 0.4 mM concentrations of the metals in Hoagland solution for 12 and 36 h. T. aestivum exhibited considerably greater accumulation of proline than P. aureus in response to the metal treatment. Among the two metals, Hg induced greater accumulation of proline than Cd. The activity of P5CS increased significantly in response to the metal treatment, particularly in T. aestivum in which the activity of the enzyme in the control was much higher than that was in P. aureus. The activity of P5CR on the other hand mostly decreased in response to the metal treatment. The study indicated a strong dependence of the metal induced proline accumulation on the constitutive P5CS content of the plants.

Light-Dark Changes in Proline Content of Barley Leaves under Salt Stress

Proline accumulation in leaves of barley (Hordeum vulgare L. cv. Alfa) seedlings treated with 150 mM NaCl was promoted in the light and suppressed in the dark. The light/dark changes of proline content was enhanced with each 12 h light/12 h dark cycle and the proline content increased steadily. Root and shoot concentrations of Na+ and Cl- in salt treated plants increased about 10 to 25 times as compared to the control. The content of these ions and the content of malondialdehyde were higher in the shoot of seedlings exposed to salt stress for 4 d in the light in comparison with the seedlings exposed to NaCl for 4 d in darkness. Light stimulated both ions and proline accumulation in the leaves and has no effect in the roots. Oxygen uptake was higher in the seedlings kept 4 d in the light which have higher endogenous free proline content. Chlorophyll fluorescence measurements showed that the photochemical activity of PS 2 slightly decreased as a result of salt stress and was not influenced by light regimes during plant growth.

Changes in Proline Content Accompanying the Uptake of Zinc and Copper by Lemna minor

Lemna minor L. grown in Hoagland solution containing zinc (10 ppm) or copper (5 ppm) for 4 d accumulated high levels of these metals. Zinc and Cu accumulation in the test plants was accompanied by a specific pattern of change in proline content. The latter showed a steep rise during early stages (peak at 12-24 h) followed by a gradual decline until 96 h of treatment. In a dose-response study, lower metal concentrations induced a sharp rise in proline level with a maximum value at 5 ppm, which declined when the concentration was further enhanced. There was a correspondence between the level of proline and total free amino acids in metal treated plants. The possibility of proline involvement in tolerance mechanisms to heavy metals has been discussed.

Amino acid pools and protein synthesis in germinating maize embryos

Amino acid pools were analyzed in maize (Zea mays L.) axes germinated for 0, 6 and 24 h. Proteins synthesized at early (0-6 h) and late (18-24 h) stages were characterized by gel electrophoresis and fluorography after either (14)C-leucine or (14)C-lysine pulses. An increase of amino acid incorporation after 18-24 h was observed, as well as changes in the protein patterns of the corresponding fluorographs. Analysis of the endogenous amino acid pools showed major changes in contents of proline, alanine, isoleucine, valine, leucine and lysine. A selective increase of lysine incorporation into proteins during the late stage was detected.

Occurrence and changes of proline content in plants in the southern Namib Desert in relations to increasing and decreasing drought

Over a period of seven years (1977-1983) the proline content and its responses to climatic changes were investigated in plants - especially Mesembryanthemaceae - in the southern Namib Desert (South Africa). Among 95 species in 26 families, 61 had detectable amounts of proline. In several of these species the proline content increased considerably in years with insufficient rainfall but decreased when the rainfall was abundant again. When individuals of the same species were grown at different sites, water availability in the soil determined their proline content. Many of the investigated species showed a clear diurnal fluctuation in their proline content with a remarkable proline accumulation during times of highest evaporative demand. In general, the higher the proline content the more pronounced were the changes, indicating that in these species-predominantly annual plants - proline was most probably involved in drought tolerance. The observation that proline accumulation and degradation reacted sensitively to changing climatic conditions over many years confirmed the correlation of proline synthesis to increasing water stress as postulated by the results of laboratory experiments with Mesembryanthemaceae.

Root Temperature Stress and Proline Content in Leaves and Roots of Two Ecologically Different Plant Species

Summary Using different root temperatures the changes in proline content in leaves and in roots of Zea mays and Avena sativa were measured. Taking the proline content as an indicator for stress the results would mean that for Avena the highest (30°C), and for Zea the lowest (10°C) applied temperature would be stress-inducing. The effects are much more pronounced in the roots than in the shoots, and proline is more prevalent in roots than tops.