Induced Proline Accumulation Research Articles

The Effects of Seed Pretreatment with Endophytic Bacteria Bacillus subtilis on the Water Balance of Spring and Winter Wheat Seedlings under Short-Time Water Deficit.

We investigated the effect of pre-sowing seed treatment with endophytic Bacillus subtilis 10-4 (B. subtilis) on spring and winter wheat (Triticum aestivum L.; cultivars Ekada-70 (Ek) and Scepter (Sc), respectively) growth and tolerance under 1-24 h of drought stress, modulated by 12% polyethylene glycol 6000 (PEG). The results showed that drought decreased transpiration intensity (TI), root relative water content (RWC), osmotic potential (Ψπ) of cell sap, and induced proline accumulation and electrolyte leakage (EL) in both wheat cultivars. It was revealed that Sc was more responsive to PEG and B. subtilis treatments than Ek. Under drought, Ek did not significantly change root length, shoot height, or dry biomass. The pretreatment of wheat plants with B. subtilis performed significantly better under drought conditions through the enhanced TI, RWC, and Ψπ of the cell sap in comparison with the plants treated with 12% PEG alone. B. subtilis also reduced stress-caused EL, especially in the Sc cultivar. Under water deficit wheat seedlings, pretreated with B. subtilis, have a higher proline accumulation in comparison to untreated stressed plants. Taken together, our results demonstrate the crucial role of endophytic B. subtilis in ameliorating the adverse effects of water stress on the water balance of both winter and spring wheat cultivars.

Arbuscular mycorrhizal fungi and endophytic fungi differentially modulate polyamines or proline of peach in response to soil flooding

Symbiotic fungi are involved in plant flooding tolerance, while the underlying mechanism is not yet known. Since polyamines and proline are also associated with stress tolerance, it is hypothesized that the enhancement of stress resistance by symbiotic fungi is associated with changes in polyamines (PAs) and/or proline. The aim of this study was to analyze the effect of inoculation with Funneliformis mosseae and Serendipita indica on growth, polyamine and its metabolism, and proline and its metabolism in peach (Prunus persica) under flooded conditions. Two-week flooding did not affect root colonization frequence of F. mosseae, while it promoted root colonization frequence of S. indica. Inoculated plants with F. mosseae and S. indica maintained relatively higher growth rates of peach under flooding than those of uninoculated plants. F. mosseae promoted root ornithine levels and arginine decarboxylase and ornithine decarboxylase activities under flooding, which promoted putrescine (Put), cadaverine (Cad) and spermidine (Spd) levels. Conversely, S. indica inhibited levels of arginine, ornithine, and agmatine and arginine decarboxylase activities, thus decreasing PAs under flooding. PAs were negatively correlated with expressions of polyamine uptake transporter 1 (PUT1) and PUT4 in peach. Transporters of polyamine (TPO) of F. mosseae and S. indica were regulated by flooding, of which FmTPO1 was positively correlated with Put, Cad, and Spd, along with a positive correlation of Spd with SiTPO1, SiTPO2, and SiTPO4. Under flooding, F. mosseae inhibited proline, while S. indica increased proline, correlated with Δ1-pyrroline-5-carboxylate synthetase 2 expressions. It thus was concluded that F. mosseae modulated polyamine accumulation while S. indica induced proline accumulation to tolerate flooding.

Abscisic acid and hydrogen peroxide regulate proline homeostasis in melon seedlings under cold stress by forming a bidirectional closed loop

Low temperatures severely limit melon cultivation and production in winter and spring. Cold stress can induce proline accumulation in melon seedlings. However, the accumulation mechanism is unclear and the way by which abscisic acid (ABA) and hydrogen peroxide (H 2 O 2 ) act as signaling molecules in the process remains unknown. We first identified key enzyme genes in the proline metabolism pathway, and identified six genes, namely, two CmP5CSs and one each of CmP5CR , CmOAT , ProDH , and CmP5CDH . Low temperature induced proline accumulation by up-regulating three synthase genes, CmP5CS1 , CmP5CR , and CmOAT , while suppressing the expressions of two catabolic genes, namely, CmProDH and CmP5CDH . Cold stress triggered ABA and H 2 O 2 synthase genes to activate their accumulation. Both H 2 O 2 and ABA pretreatments enhanced melon seedling’s cold tolerance, but the two behaved divergently in proline metabolism. Exogenous H 2 O 2 enhanced or maintained the aforementioned induction efficiency of low temperature. In contrast, ABA only induced CmP5CR and CmOAT expression, with no effect on CmP5CS1 , and synchronously induced CmProDH and CmP5CDH expressions, leading to a slight reduction in proline content. Alternatively, ABA controlled proline homeostasis under cold stress, at least in part, by inhibiting H 2 O 2 generation. Overall, the results suggest that ABA and H 2 O 2 formed a fine bidirectional closed loop to regulate proline homeostasis in melon seedlings. • Proline metabolism genes in melon were identified for the first time. • Cold induced proline accumulation by promoting CmP5CS1 , CmP5CR , CmOAT expression, and inhibiting CmProDH , CmP5CDH expression. • Exogenous H 2 O 2 induced proline and ABA accumulation for cold tolerance improvement. • ABA inhibited H 2 O 2 generation to keep proline homeostasis under cold stress.

Toxicity assessment of metribuzin and its amelioration through plant growth regulators in Vigna radiata (L.) R. Wilczek.

The present experiment was conducted to evaluate the metribuzin-induced stress response in Vigna radiata and to explore the ameliorative role of exogenous application of plant growth regulators (PGRs) against metribuzin toxicity by assessing important biochemical and yield parameters. Prior to the field experiment, dose standardization experiments were performed, and EC50 was calculated for metribuzin. On day 21, field grown V. radiata plants were treated with graded concentrations of metribuzin (0-1000mg [Formula: see text]). Plants treated with 600mg [Formula: see text] (EC50) and 1000mg [Formula: see text] (highest dose) of metribuzin were co-treated individually and simultaneously with gibberellic acid-3 (GA), indole-3 acetic acid (IAA), and salicylic acid (SA). After 7days of treatment, leaf tissues were analyzed for biochemical parameters, whereas those related to yield were recorded during harvest. The result of this study indicated that metribuzin treatment to V. radiata resulted in increase in lipid peroxidation and reduce chlorophyll and carotenoid contents as well as yield parameters. However, metribuzin-treated plants induced proline accumulation and activity of antioxidant enzymes. Exogenous application of GA, IAA, and SA significantly reduced lipid peroxidation and increased contents of photosynthetic pigments, proline, and antioxidant enzymes thereby increasing yield parameters. It was observed that during metribuzin stress, SA exhibited a better ameliorative response out of the three exogenously applied PGRs, while the combined use of all PGRs exhibited much improved ameliorative response on biochemical and yield parameters of plants.

Foliar Application of Salicylic Acid Improves Salt Tolerance of Sorghum (Sorghum bicolor (L.) Moench).

It has been reported that around the world, approximately 19.5% of all irrigated land and 2.1% of dry land is affected by salt stress, and these percentages continue to increase. Sorghum is the fifth most important cereal in the world and therefore research on its salt tolerance is of global importance. In our research, we focused on foliar application of salicylic acid (SA) on salt-stressed sorghum. We performed a pot experiment with two salt levels (0 and 100 mM sodium chloride NaCl) and five SA concentrations (0, 50, 100, 150 and 200 mg/L). Our results suggest that in saline conditions foliar application of SA induced an adaptive response to salinity by inducing proline accumulation as well as antioxidant enzymes activities and enhanced the protection of the photosynthetic machinery, maintained photosynthesis activities, and improved the growth of sorghum plants. These alleviation effects were depended on applied SA concentration. Under saline condition 150 mg/L, SA was the most effective for relieving the adverse effect of salt stress. Under non-saline conditions 100 mg/L SA was the best for improving sorghum growth and dry matter production. Our results demonstrated that foliar SA application is effective in improving sorghum growth under salinity.

PHYSIOLOGICAL RESPONSES AND TOLERANCE EFFICIENCY OF Spinacea oleracea L. UNDER HYDROPONIC Ni2+ STRESS CONDITION

An indoor EDTA and HNO3 enriched environment was created by an injection system with timing and varying concentration control. Spinacea oleracea was selected hydroponic plant exposed to various doses of Ni2+ (0, 1000, 2000 and 4000 mg/L) as Na2EDTA at (0, 500 and 3000 mg/L) and (0,500 and 3000 mg/L) HNO3 in different combinations for 6 days with 10-hour-treatment each day. This study used modified Hoagland nutrient culture in a screen house to provide an ideal environment for comparing the efficiency of chelate-assisted and unchelated phytoextraction of Ni2+ by S. oleracea. Changes in morphological characteristics including leaf damage rate to evaluate morphological resistance to Ni2+ uptake and proline contents was observed. Changes in fresh biomass were significant (p < 0.05) with respect to addition of EDTA and HNO3 at different concentration to different concentrations of Ni2+ compared to unchelated treatments of same concentrations of Ni2+. The Ni2+ induced proline accumulation in shoots increased significantly (P < 0.05) with increasing Ni2+ concentrations.

The immediate effect of riboflavin and lumichrome on the mitigation of saline stress in the microalga Chlorella sorokiniana by the plant-growth-promoting bacterium Azospirillum brasilense

This study assessed the early effects of riboflavin and lumichrome produced by the bacterium Azospirillum brasilense on mitigating the stress of salinity on the growth and metabolic status of Chlorella sorokiniana. C. sorokiniana was grown in a synthetic growth medium (SGM) at three salt levels (0%, 1.5%, and 3% NaCl) and under four treatments: (1) C. sorokiniana growing alone; (2) C. sorokiniana co-cultured with A. brasilense; (3) C. sorokiniana supplemented with synthetic riboflavin; and (4) C. sorokiniana supplemented with lumichrome, mimicking the riboflavin and lumichrome concentrations naturally produced by A. brasilense. Cell density, total carbohydrates, total and neutral lipids, chlorophyll a and b, and carotenoids contents, proline accumulation, and activity of superoxide dismutase (SOD) were analyzed. Increasing salinity affected the growth rate, cell size, and cell density of C. sorokiniana, induced proline accumulation, and made the total-lipid concentration higher than the carbohydrate concentration. The neutral lipids, chlorophylls, and SOD showed higher values at 1.5% NaCl. Riboflavin and lumichrome showed significant effects on the analyzed variables. Lumichrome at 1.5% salinity induced an early but transient growth response, making carbohydrate production higher than the total lipid production. By contrast, riboflavin enhanced SOD activity and reduced proline accumulation at all the salinity levels. Longer incubation times resulted in effects similar to those of lumichrome in the analyzed metabolites, thus suggesting the conversion of riboflavin into lumichrome. The microalga−bacteria co-cultures at all salinity levels exhibited growth promotion, with consistent effects at the different incubation times and superior magnitude to that presented by lumichrome or riboflavin alone, showing an alleviating effect of the saline stress through osmoregulation with increased carbohydrate concentration and antioxidant activity, but not with increased proline or total lipid concentration. These findings suggest that Azospirillum brasilense can be used as an alternative to mitigate saline stress effects in microalgae cultured in low-salinity waters.

A Wild Allele of Pyrroline-5-Carboxylate Synthase1 Leads to Proline Accumulation in Spikes and Leaves of Barley Contributing to Improved Performance Under Reduced Water Availability.

Water stress (WS) during spike development strongly affects final grain yield and grain quality in cereals. Proline, an osmoprotectant amino-acid, may contribute to alleviating the effects of cell and tissue dehydration. We studied five spring barley genotypes contrasting in their drought response, including two introgression lines, S42IL-143 and S42IL-141, harboring a Pyrroline-5-carboxylate synthase1- P5cs1 allele originating from the wild barley accession ISR42-8. We tested the hypothesis that barley genotypes harboring a wild allele at P5cs1 locus are comparatively more drought-tolerant at the reproductive stage by inducing proline accumulation in their immature spikes. At the booting stage, we subjected plants to well-watered and WS treatments until physiological maturity. Several morpho-physiological traits had significant genotype by treatment interaction and reduction under WS. Varying levels of genotypic proline accumulation and differences in WS tolerance were observed. Spike proline accumulation was higher than leaf proline accumulation for all genotypes under WS. Also, introgression lines carrying a wild allele at P5cs1 locus had a markedly higher spike and leaf proline content compared with the other genotypes. These introgression lines showed milder drought symptoms compared with elite genotypes, remained photosynthetically active under WS, and maintained their intrinsic water use efficiency. These combined responses contributed to the achievement of higher final seed productivity. Magnetic resonance imaging (MRI) of whole spikes at the soft dough stage showed an increase in seed abortion among the elite genotypes compared with the introgression lines 15 days after WS treatment. Our results suggest that proline accumulation at the reproductive stage contributes to the maintenance of grain formation under water shortage.

Screening of ‘King’ mandarin (Citrus nobilis Lour) × Poncirus trifoliata ((L.) Raf.) hybrids as salt stress-tolerant citrus rootstocks

This work evaluates new citrus hybrid tolerance to salt stress compared to Carrizo citrange. Growth parameters, ion concentration, photosynthetic parameters, leaf water relation, plant damage and proline concentration were assessed in plants irrigated with 0 (control) or 60 mM of NaCl for 60 days. Some hybrids presented marked salt-stress symptomatology like sharp decreases in plant biomass and RGR parameter, and high leaf burn and abscission percentages. While Cl− accumulation in most salinised genotypes was recorded in all the plant fractions, accumulation occurred in some hybrids only in their aerial organs. Stomatal conductance also lowered under salt conditions in all the hybrids, whereas the internal CO2 concentration (Ci) tended to increase. Salt stress lowered the leaf water potentials in all the 0501 hybrids. As a response, the salinised plants induced proline accumulation. The main trait that improved salt tolerance in some genotypes is apparently linked with the imbalance among Cl−, Na+ and K+ ions, especially enhanced K+ uptake and transport rates which delay plant damage.

Mycorrhizal fungi enhance flooding tolerance of peach through inducing proline accumulation and improving root architecture

This study aimed to evaluate the effect of an arbuscular mycorrhizal fungus (AMF) Glomus mosseae on plant growth, root architecture, and proline metabolism in roots of peach (Prunes persica L.) under non-flooding and flooding conditions. The 12-day flooding dramatically inhibited root colonisation of G. mosseae, but induced a large number of extraradical mycelia. Although the flooding treatment also relatively inhibited growth and root architecture of peach, the mycorrhizal fungal inoculation dramatically increased shoot and root biomass, plant height, stem diameter, number of 1<sup>st</sup>- and 2<sup>nd</sup>-order lateral roots, root total length (mainly 0–1 cm and > 3 cm long), root surface area, and root volume under flooding. The study also revealed distinctly higher proline accumulation in the roots of mycorrhizal plants than non-mycorrhizal plants under both non-flooding and flooding conditions, accompanied by higher Δ<sup>1</sup>-pyrroline-5-carboxylate synthase (P5CS) activity and lower δ-ornithine transaminase and proline dehydrogenase activities. In addition, the PpP5CS1 gene expression was up-regulated by flooding and mycorrhization. This study concluded that mycorrhizal fungi enhanced flooding tolerance of peach through inducing proline accumulation and improving root architecture.

Seed priming with sodium nitroprusside attenuates the effects of water deficit on soybean seedlings

Considering that water deficit is one of the main environmental factors responsible for low soybean yield and that nitric oxide (NO) has been shown to be a fundamental part of plant defense signaling during stress, the aim of the present study was to evaluate the effect of seed priming with nitric oxide on the induction of water deficit tolerance during the initial development of soybean. Thus, seeds were treated with 0 (water only), 50, 100 or 250 μmol.L-1 sodium nitroprusside for 6 hours. Additionally, untreated seeds were used. After drying, the seeds were placed in containers filled with a commercial substrate mixture and vermiculite and irrigated to 100% and 50% field capacity. Biometric and biochemical evaluations (pigment and proline contents) were performed after 14 days. It was concluded that pretreatment of soybean seeds with 50 to 250 μmol.L-1 SNP attenuated the effects of water deficit on stem growth, leaf area, and shoot dry matter and induced carotenoid biosynthesis. The accumulation of proline in the leaves was pronounced in the treatments with 100 and 250 μmol.L-1 SNP, while 100 μmol.L-1 SNP induced proline accumulation in the roots.

Stress Adaptive Plasticity: Aegilops tauschii and Triticum dicoccoides as Potential Donors of Drought Associated Morpho-Physiological Traits in Wheat.

The inconsistent prevalence of abiotic stress in most of the agroecosystems can be addressed through deployment of plant material with stress adaptive plasticity. The present study explores water stress induced plasticity for early root-shoot development, proline induction and cell membrane injury in 57 accessions of Aegilops tauschii (DD-genome) and 26 accessions of Triticum dicoccoides (AABB-genome) along with durum and bread wheat cultivars. Thirty three Ae. tauschii accessions and 18 T. dicoccoides accessions showed an increase in root dry weight (ranging from 1.8 to 294.75%) under water stress. Shoot parameters- length and biomass, by and large were suppressed by water stress, but genotypes with stress adaptive plasticity leading to improvement of shoot traits (e.g., Ae tauschii accession 14191 and T. dicoccoides accession 7130) could be identified. Water stress induced active responses, rather than passive repartitioning of biomass was indicated by better shoot growth in seedlings of genotypes with enhanced root growth under stress. Membrane injury seemed to work as a trigger to activate water stress adaptive cellular machinery and was found positively correlated with several root-shoot based adaptive responses in seedlings. Stress induced proline accumulation in leaf tissue showed marked inter- and intra-specific genetic variation but hardly any association with stress adaptive plasticity. Genotypic variation for early stage plasticity traits viz., change in root dry weight, shoot length, shoot fresh weight, shoot dry weight and membrane injury positively correlated with grain weight based stress tolerance index (r = 0.267, r = 0.404, r = 0.299, r = 0.526, and r = 0.359, respectively). In another such trend, adaptive seedling plasticity correlated positively with resistance to early flowering under stress (r = 0.372 with membrane injury, r = 0.286 with change in root length, r = 0.352 with change in shoot length, r = 0.268 with change in shoot dry weight). Overall, Ae. tauschii accessions 9816, 14109, 14128, and T. dicoccoides accessions 5259 and 7130 were identified as potential donors of stress adaptive plasticity. The prospect of the study for molecular marker tagging, cloning of plasticity genes and creation of elite synthetic hexaploid donors is discussed.

Water stress induced proline accumulation and antioxidative enzymes in groundnut (Arachis hypogaea L.)

Thirty days grown seedlings of eight genotypes of groundnut viz. RHRG-6083, TAG-24, TG-60(LC), Karad-4-11, SB-XI, RHRG-6097, RHRG-6021, and RHRG-6055 were subjected to moisture stress by withholding irrigation for 15 days in pot culture experiment in order to evaluate its effect of on RWC , proline accumulation, soluble proteins, chlorophyll content and activities of superoxide dismutase (SOD), peroxidase (POX), glutathione reductase (GR) and lipid peroxidation (MDA).The levels of proline, soluble protein and the activity of all four antioxidative enzymes were found to be increased with MDA content in all genotypes of groundnut during water stress, however the chlorophyll and RWC content were found to be decreased. This study revealed that under water stress condition SB-XI, TAG-24 and RHRG-6021 showed higher increase of proline content and activities of antioxidative enzymes with lower reduction in RWC and chlorophyll. These three genotypes are stable during stress and seems to be promising for drought tolerance.

Effect of salinity on some physiological and biochemical responses in the cyanobacterium Synechococcus elongatus

In this study, some physiological and biochemical responses of Synechococcus elongatus to salt stress were investigated. The cyanobactrium was grown in BG-11 medium under different concentrations of NaCl (0, 0.5, 1 M). The results indicated that the growth of S. elongatus was significantly inhibited under salt stress on days 5, 9 and 12. Protein content increased in S. elongatus on day 12 in presence of salt. Salinity induced proline accumulation at 1 M NaCl on day 12 and caused a significant enhance in hydrogen peroxide content on day 5. Catalase (CAT) activity continuously increased on day 5. An increasing trend in polyphenol oxidase (PPO) activity was indicated on days 5 and 9. Superoxide dismutase (SOD) activity gradually induced with increasing NaCl concentrations on day 5. Salt stress decreased chlorophyll content compared to that of control in three stages of growth, and carotenoid content declined on days 9 and 12. The contents of phycobiliprotein (PBP), phycoerythrin (PE) and phycocyanin (PC) enhanced significantly under different NaCl concentrations on days 5 and 9. These results show that S. elongatus has limited adaptative potential to salinity, and the optimum medium for its culture should not bear NaCl even at a moderate level, if production of carotenoids is aimed.

Effects of Calcium and Calmodulin Antagonists on Chilling Stress-Induced Proline Accumulation in Jatropha curcas L.

Regulation of proline accumulation in plants under chilling stress remains unclear. In this paper, we treated Jatropha curcas seedlings under chilling stress with exogenous calcium chloride (CaCl2), the plasma membrane Ca2+-channel blocker lanthanum chloride (LaCl3), calmodulin antagonists, chlorpromazine (CPZ), and trifluoperazine (TFP) and investigated the effects of calcium and calmodulin (CaM) on proline accumulation and chilling tolerance. The results showed that CaCl2 treatment significantly enhanced chilling stress-induced proline accumulation. CaCl2 also induced an almost immediate and rapid increase of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and glutamate dehydrogenase activities, the key enzymes in the glutamate pathway of proline biosynthesis, and up-regulated P5CS expression, but it decreased the activity of proline dehydrogenase (ProDH), a key enzyme of proline degradation, and inhibited ProDH expression. Treatment with LaCl3, CPZ, and TFP exhibited the opposite effects to those by CaCl2 treatment. Moreover, CaCl2, LaCl3, CPZ, and TFP had little effect on the activities of ornithine aminotransferase and arginase, the key enzymes in the ornithine pathway of proline biosynthesis. These results indicated that Ca2+-CaM might be involved in signal transduction events, leading to proline accumulation in J. curcas seedlings under chilling stress, and that Ca2+-induced proline accumulation is a combined result of the activation of the glutamate pathways of proline biosynthesis and the simultaneous inhibition of the proline degradation pathway. In addition, CaCl2 treatment increased tissue vitality, decreased the content of the lipid peroxidation product malondialdehyde (MDA), and alleviated electrolyte leakage in J. curcas seedlings under chilling stress, indicating that exogenous Ca2+ can enhance chilling tolerance, and proline might be a key factor in this increased chilling tolerance.

Effects of Ascorbic Acid and Reduced Glutathione on the Alleviation of Salinity Stress in Olive Plants

ABSTRACTThe aim of this study was to evaluate the effects of low molecular mass antioxidants and NaCl salinity on growth, ionic balance, proline, and water contents of ‘Zard’ olive trees under controlled greenhouse conditions. The experiment was carried out by spraying 2 mM of ascorbic acid (Asc) and 3 mM of reduced glutathione (GSH) on the plants that were treated with two salinity levels (0 and 100 mM NaCl) on their root medium. Plant growth parameters (leaf fresh weight, leaf dry weight, leaf number, total fresh weight, and total dry weight) were significantly improved by Asc compared with growth parameters in GSH and control plants. Higher concentrations of Na+ and Cl– were observed in salt-stressed plants, while Na+ and Cl– concentrations were decreased in the olive leaves that were sprayed with Asc. Salinity in the root zone caused a considerable decline in both K+ concentration and K/Na ratio. K+ concentration and K/Na ratio were significantly increased by application of Asc on plant leaves. Salinity caused an increase in electrolyte leakage (EL) compared with the control plants. Lowest EL and tissue water content (TWC) was obtained in Asc-sprayed plants, whereas TWC was increased in salt-stressed plants. Plants were subjected to salt stress and showed a higher relative water content (RWC) than the control plants. Salt stress induced proline accumulation in olive leaves. In conclusion, exogenous application of Asc is recommended to improve tolerance of olive plants under saline conditions.

Overexpression of D-amino acid oxidase from Bradyrhizobium japonicum, enhances resistance to glyphosate in Arabidopsis thaliana.

The glyphosate resistance in Escherichia coli and Arabidopsis was due to D-amino acid oxidase expression. Transgenic glyphosate-resistant crops have a high percentage in the total area devoted to transgenic crops worldwide. D-amino acid oxidase (DAAO) can metabolize glyphosate by oxidative cleavage of the carbon-nitrogen bond on the carboxyl side and yield aminomethyl phosphonic acid and glyoxylate, which are less toxic to plants than glyphosate. To date, reports on the use of DAAO to enhance glyphosate resistance in plants are lacking. In this paper, we report synthesis, and codon usage optimization for plant expression, of the DAAO gene by successive polymerase chain reaction from Bradyrhizobium japonicum. To confirm the glyphosate resistance of the DAAO gene, the recombinant plasmid pYPX251 (GenBank Accession No: AY178046) harboring the wild-type DAAO gene was transformed into DH5α. The positive transformants grew well both on solid and in liquid M9 medium containing 200 mM glyphosate. The optimized DAAO gene was transformed into Arabidopsis and 9 days after application of 10 mM glyphosate, the 4-week-old wild-type plants all died; by contrast, transgenic plants could grow normally. The proline content and peroxidase activity showed that glyphosate could induce proline accumulation and produce reactive oxygen species.

Estresse térmico no acúmulo de prolina livre de plântulas de guandu oriundas de sementes tratadas com poliaminas

It was studied the effects of seed treatment with polyamines of pigeonpea for proline content of seedling in order to verify that the application of these polyamines attenuates temperature stress on germination and early seedling growth, and see if exogenous putrescine and spermidine induce the accumulation of proline, this amino acid may be biochemical and physiological indicator in seedlings that are under suboptimal temperatures and supraoptmail. The seeds of pigeonpea cv. BRS Mandarin and cv. Caqui, treated with a solution of 0.5 mM of putrescine and spermidine, were subjected to suboptimal temperature (20oC, 18oC, 16oC and 14oC) and supraoptimal (36oC, 38oC, 40oC and 44oC) for 24 hours and 48 hours. After these periods, were subjected to 25°C until day 10, when the percentage of seed germination were observed, the proline content of vegetative parts and the dry mass of the seedlings. A completely randomized design in a factorial arrangement was used 3x4x2+3 (solutions with polyamines, temperature stress by cooling/heating, time of exposure to stress, plus additional factors em25oC with 0.0 mM and 0.5mM of Put and Spd), with four replicates of 25 seeds. The results were submitted to analysis of variance and means were compared by Tukey test at 5% probability, separately for each cultivar. Both exogenous polyamines attenuate the effects of cooling and heating, contributing to the growth of germinated seeds. Also, putrescine and spermidine exogenous mitigated the adverse effects by inducing proline accumulation, which leads to osmotic adjustment temperatures, although this physiological response has not minimized the negative effects of temperature stress on seedling growth of pigeonpea. Proline can be considered biochemical and physiological indicator in seedlings of both cultivars of pigeonpea treated with polyamines under temperature stress.

Influence of Diazotrophic Bacteria on Antioxidant Enzymes and Some Biochemical Characteristics of Soybean Subjected to Water Stress

Drought stress is an abiotic stress that imposes serious constraints on plants. The present investigation was carried out to determine the inter-relationship between some physiological attributes of soybeans affected by drought stress and pure isolates of Azotobacter and Azospirillum. Drought stress and bacterial application increased catalase and glutathione peroxidase activity, whereas drought stress increased superoxide dismutase activity during the pod-filling stage. Abscisic acid and proline levels increased due to drought stress and bacterial application during the flowering stage, whereas total plant nitrogen was enhanced under well-watered conditions when plants were inoculated with bacteria. The close relationship between enzyme activity and drought stress with bacteria indicated that antioxidant enzymes play an important role in alleviating the detrimental effects of water stress. In addition, the enhancement of abscisic acid and proline could be positively linked with drought stress, and drought-induced abscisic acid could induce proline accumulation and the expression of antioxidant enzyme genes.

Exogenous ornithine is an effective precursor and the δ-ornithine amino transferase pathway contributes to proline accumulation under high N recycling in salt-stressed cashew leaves

The role of the δ-ornithine amino transferase (OAT) pathway in proline synthesis is still controversial and was assessed in leaves of cashew plants subjected to salinity. The activities of enzymes and the concentrations of metabolites involved in proline synthesis were examined in parallel with the capacity of exogenous ornithine and glutamate to induce proline accumulation. Proline accumulation was best correlated with OAT activity, which increased 4-fold and was paralleled by NADH oxidation coupled to the activities of OAT and Δ 1-pyrroline-5-carboxylate reductase (P5CR), demonstrating the potential of proline synthesis via OAT/P5C. Overall, the activities of GS, GOGAT and aminating GDH remained practically unchanged under salinity. The activity of P5CR did not respond to NaCl whereas Δ 1-pyrroline-5-carboxylate dehydrogenase was sharply repressed by salinity. We suggest that if the export of P5C from the mitochondria to the cytosol is possible, its subsequent conversion to proline by P5CR may be important. In a time-course experiment, proline accumulation was associated with disturbances in amino acid metabolism as indicated by large increases in the concentrations of ammonia, free amino acids, glutamine, arginine and ornithine. Conversely, glutamate concentrations increased moderately and only within the first 24 h. Exogenous feeding of ornithine as a precursor was very effective in inducing proline accumulation in intact plants and leaf discs, in which proline concentrations were several times higher than glutamate-fed or salt-treated plants. Our data suggest that proline accumulation might be a consequence of salt-induced increase in N recycling, resulting in increased levels of ornithine and other metabolites involved with proline synthesis and OAT activity. Under these metabolic circumstances the OAT pathway might contribute significantly to proline accumulation in salt-stressed cashew leaves.