Higher Proline Accumulation Research Articles

Proteome Analysis of the Gametophytes of a Western Himalayan Fern Diplazium maximum Reveals Their Adaptive Responses to Changes in Their Micro-Environment.

Ferns have survived changing habitats and environmental extremes of different eras, wherein, the exploratory haploid gametophytes are believed to have played a major role. Therefore, the proteome of in vitro grown gametophytes of a temperate Himalayan fern, Diplazium maximum in response to 0 (G0), 1 (G1), and 3% (G3) sucrose was studied. A total of 110 differentially abundant protein spots (DAPs) were obtained. Among these, only 67 could be functionally categorized as unique proteins involved in various metabolic processes. Calcium dependent proteins, receptor like kinases, G proteins, proteins related to hormonal signaling and their interaction with other pathways, and regulatory proteins were recorded indicating the involvement of five different signaling pathways. DAPs involved in the activation of genes and transcription factors of signaling and transduction pathways, transport and ion channels, cell-wall and structural proteins, defense, chaperons, energy metabolism, protein synthesis, modification, and turnover were identified. The gametophytes responded to changes in their micro-environment. There was also significant increase in prothallus biomass and conversion of two-dimensional prothalli into three-dimensional prothallus clumps at 3% sucrose. The three-D clumps had higher photosynthetic surface area and also closer proximity for sexual reproduction and sporophyte formation. Highest accumulation of proline, enhanced scavenging of reactive oxygen species (ROS) and DAPs of mostly, abiotic stress tolerance, secondary metabolite synthesis, and detoxification at 3% sucrose indicated an adaptive response of gametophytes. Protein Protein Interaction network and Principal Component analyses, and qRT-PCR validation of genes encoding 12 proteins of various metabolic processes indicated differential adjustment of gametophytes to different levels of sucrose in the culture medium. Therefore, a hypothetical mechanism was proposed to show that even slight changes in the micro-environment of D. maximum gametophytes triggered multiple mechanisms of adaptation. Many DAPs identified in the study have potential use in crop improvement and metabolic engineering programs, phytoremediation and environmental protection.

Melatonin Stimulates Activities and Expression Level of Antioxidant Enzymes and Preserves Functionality of Photosynthetic Apparatus in Hickory Plants (Carya cathayensis Sarg.) under PEG-Promoted Drought

Nowadays, drought is one of the major abiotic factors which negatively affects growth and development of several fruit tree species, including Chinese hickory plants (Carya cathayensis Sarg.). The present investigation was conducted to study the possible positive effects of melatonin in drought resistance of C. cathayensis plants along with associated mechanisms. It was observed that melatonin pre-treatment applied before limited water availability significantly contrasted drought-promoted negative effects in terms of plant growth and physiological responses. Significant improvement was observed in key biological parameters like relative water content, net photosynthetic rate, stomatal conductance, transpiration rate, maximum photosynthetic efficiency of photosystem II (PSII), and PSII electron transport rate. Antioxidant apparatus was also stimulated by melatonin and enhanced activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were noticed along with higher accumulation of proline. Gene expression studies herein revealed that melatonin promoted the up-regulation of the expression of SOD (70.7%), CAT (32.7%), and APX (66.5%) genes. As a consequence, accumulation of malondialdehyde by-products and leaf symptoms were reduced in melatonin-treated plants. All these observations offer the clear evidence that pre-treatment with melatonin ameliorate the performance of Chinese hickory plants against drought stress.

Effect of foliar seawater application on berry quality and ion distribution of ‘Kyoho’ grapevine yards

Extensive research has been conducted over the years to investigate the diverse effects of seawater on many crop plants either by irrigation or foliar spray in an attempt to enhance the yield and quality. The purpose of this study was to quantitatively determine the effects of foliar seawater application on berry quality and ion distribution of ‘Kyoho’ grape vineyards. A field experiment was conducted using diluted seawater starting at veraison followed by seven-day intervals between the treatments. While leaf contained K+ as much as Ca2+, which was at least eight times higher than Mg2+ and Na+, berry displayed different profiles as shown by significant decreases in K+ (22.4%) and Mg2+ (30.8%) with almost no changes in Ca2+ and Na+. Concentrations of cations were much higher than those of anions in control vineyard soil under this study. Foliar seawater treatment did not change the amounts of K+, Na+, HCO3−, and NO3− but significantly increased the amounts of Ca2+, Mg2+, and Cl− in vineyard soil. Declined ratios of K+/Na+ and Mg2+/Na+ were observed in both leaf and berry after foliar seawater application, but percentages in the declined ratios were significantly higher in leaf. In contrast to berry and leaf, vineyard soil had significantly increased ratios of Mg2+/Na+ and Ca2+/Na+ along with an unchanged ratio of K+/Na+ after foliar seawater application. Substantially decreased activities of antioxidant defensive enzymes (CAT, POD and APX) were observed in the post-seawater treatment leaves. Foliar seawater application resulted in high accumulation of proline, soluble proteins, and malondialdehyde (MDA), as well as an improved soluble solid content (SSC), redness, and color index for red grapes (CIRG) in berries without losing weight, firmness and yield. Leaf SPAD (chlorophyll value of leaf), soluble sugar and starch in branch were not affected despite the elevated level of Cl- in soil by foliar seawater treatment. Taken all the results together, foliar seawater treatment starting at veraison could be useful for improving ‘Kyoho’ grape berry quality without affecting the vegetative growth under the soil conditions used in this study.

Review on Role of Proline on Coffee Under Drought Conditions

Drought is one of the major constraints that limiting production of crop worldwide. Plants tolerate drought by many ways like morphological, physiological and biochemical tolerance mechanisms. Plants develop mechanisms to tolerant abiotic stress by osmotic adjustment that is usually accomplished by uptake of inorganic ions, as well as the accumulation of proline. Proline is a universal osmo-protectant and acts as an osmolyte and antioxidant, and it is one of the most important compatible solutes that play a vital role in osmotic adjustment in crops under drought stress. Accumulation of proline considered as adaptive mechanisms in drought-tolerant coffee genotypes. In general, more attention on biochemical traits for drought tolerant mechanisms on coffee should be given. Therefore, looking for high proline accumulation genotype under drought conditions is important for further coffee breeding program to release drought tolerant genotypes. Keywords: Coffee, Drought, Tolerant, Proline Accumulation DOI : 10.7176/JEES/9-10-01 Publication date :October 31 st 2019

Bacteria-assisted phytoremediation of fuel oil and lead co-contaminated soil in the salt-stressed condition by chromolaena odorata and Micrococcus luteus

Bioremediation of lead-petroleum co-contaminated soil under salt-stressed condition has been investigated. In this study, the co-contaminated soil (780 mg kg−1 Pb and 27,000 mg kg−1 TPHs) under the high salinity (EC 7.79 ds m−1) was used as a model soil to be remediated by Chromolaena odorata inoculated with Micrococcus luteus. The results showed that salt stress caused a marked reduction in dry biomass and stem height, and high accumulation of proline. The presence of salt did not affect the total amount of chlorophyll in plant tissues. No toxicity symptoms were evident from plant morphology after three months of exposure. Drastic differences in the accumulation patterns of Pb in C. odorata grown on saline and non-saline soils were observed and indicated that salinity negatively affected Pb uptake and accumulation. A high rate of degradation of TPHs was observed in non-saline soils with or without bacterial inoculation. Salinity stress showed no significant different in the proportion of TPH degradation with added or non-added M. luteus. The tolerance of C. odorata and M. luteus to moderate concentrations of Pb and fuel oil made them very good candidates for the use in bacteria-assisted phytoremediation of lead-fuel oil co-contaminated soils under the mild saline soils.

Effective use of zinc oxide nanoparticles through root dipping on the performance of growth, quality, photosynthesis and antioxidant system in tomato

The objective of the study was to explore the effect of zinc oxide nanoparticles (ZnO-NPs) through root treatment on growth biomarkers, photosynthetic traits, activities of carbonic anhydrase and various antioxidant enzymes as well as the yield of tomato plants. 20 days old seedlings of tomato (cv. PKM-1) were dipped in double distilled water (control), 10, 50, 100 or 200 ppm of ZnO-NPs for 15, 30 or 45 min, respectively. At the stage of 45 and 60 days after sowing (DAS), the plants developed from ZnO-NPs (10 ppm for 30 min) showed improved growth and photosynthetic attributes, enhanced activity of various antioxidant enzymes (e.g., catalase, peroxidase and superoxide dismutase) and higher accumulation of proline and protein content over the non-treated plant. The fruits number and yield in ZnO-NPs treated plants (10 ppm; 30 min) were higher whereas ascorbic acid was lower than the non-treated plant. These fruits possessed higher levels of β-carotene and lycopene content. The root dipping with 10 ppm for 30 min of ZnO-NPs was found to be best for most of the evaluated parameters.

Rootstock scion interaction effects on biochemical and gas exchange drought tolerant traits in arabica (Coffea arabica L.) coffee

Studies were conducted using four elite rootstock scion combinations of arabica coffee and respective pure line scion materials to understand drought tolerance ability by studying the changes in biochemical, chlorophyll fractions and photosynthetic parameters at different soil moisture regimes. The results indicated significant (p < 0.05) reduction in relative water content, nitrate reductase activity, carbohydrate and starch content besides increase in epicuticular wax, free proline, protein content at water stress conditions in rootstock scion combinations and counterpart pure line scion seedlings. At water stress conditions Sln.10 scion on Sln.11 rootstock and S.795 and S.4202 scions on Sln.9 rootstock maintained significantly (p < 0.05) higher relative water content, net photosynthesis, carboxylation efficiency, instantaneous water use efficiency, nitrate reductase enzyme activity, mesophyll efficiency along with high accumulation of epicuticular wax, free proline, total protein and Chlorophyll `b’ content. Maintenance of higher carbohydrate and starch content and recovery to normalcy after the alleviation of stress was observed in these rootstock scion combinations compared to pure line scion seedlings and other combinations indicating better drought endurance ability of these combinations. These combinations could be assessed in the field for yield components and further for commercial exploitation.

Identification of Factors Linked to Higher Water-Deficit Stress Tolerance in Amaranthus hypochondriacus Compared to Other Grain Amaranths and A. hybridus, Their Shared Ancestor.

Water deficit stress (WDS)-tolerance in grain amaranths (Amaranthus hypochondriacus, A. cruentus and A. caudatus), and A. hybridus, their presumed shared ancestor, was examined. A. hypochondriacus was the most WDS-tolerant species, a trait that correlated with an enhanced osmotic adjustment (OA), a stronger expression of abscisic acid (ABA) marker genes and a more robust sugar starvation response (SSR). Superior OA was supported by higher basal hexose (Hex) levels and high Hex/sucrose (Suc) ratios in A. hypochondriacus roots, which were further increased during WDS. This coincided with increased invertase, amylase and sucrose synthase activities and a strong depletion of the starch reserves in leaves and roots. The OA was complemented by the higher accumulation of proline, raffinose, and other probable raffinose-family oligosaccharides of unknown structure in leaves and/or roots. The latter coincided with a stronger expression of Galactinol synthase 1 and Raffinose synthase in leaves. Increased SnRK1 activity and expression levels of the class II AhTPS9 and AhTPS11 trehalose phosphate synthase genes, recognized as part of the SSR network in Arabidopsis, were induced in roots of stressed A. hypochondriacus. It is concluded that these physiological modifications improved WDS in A. hypochondriacus by raising its water use efficiency.

Physiological Responses of Contrasting Rice Genotypes to Salt Stress at Reproductive Stage

Salinity is a major abiotic stress affecting plant growth and productivity. Considerable genetic variation is present in rice in response to salt stress, with higher sensitivity during early seedling and reproductive stage. In this study, physiological changes in leaves and developing panicles of rice genotypes (IR686, Sadri, Rc222, CSR28, IR670 and Pokkali) contrasting in salt tolerance at the reproductive stage were evaluated in greenhouse experiment under salt stress. The results showed that IR670 and the tolerant-check Pokkali maintained lower Na+/K+ ratio, less reduction in chlorophyll concentration, lower malondialdehyde (MDA) production, higher concentrations of reduced ascorbate (reduced AsA), higher proline accumulation and lower percentage reduction in pollen viability than the salt-sensitive genotypes under salt stress. The higher concentration of reduced AsA suggests an efficient ROS-scavenging system. Physiological measurements and pollen viability analysis revealed that Sadri (moderately tolerant at the seedling stage) is sensitive to salt stress at the flowering stage. The findings will be useful in breeding salt tolerant varieties at both seedling and reproductive stages by selecting appropriate genotypes and phenotypes.

Evaluation of biochemical and physiological responses of salsola spp at their natural habitats

Halophytes are naturally salt-tolerant plants that are useful for soil remediation applications. Biochemical and physiological responses of Salsola species, namely; S. ruthenica, S. dendroides and S. crassa were evaluated at their natural habitats for their salt tolerance in which the biochemical responses such as peroxidase (POX, EC.1.11.1.7) and catalase (CAT, EC.1.11.1.6) enzymes, inorganic ion accumulation, proline (Pro), malondialdehyde (MDA), chlorophyll contents (Chl-a, Chl-b) were measured. The results showed that variation existed in Salsola spp. in their response to salinity. Although all Salsola spp. showed similar trends, S. ruthenica expressed higher activities of antioxidant enzymes along with the higher accumulation of proline, MDA contents than those of S. dendroides and S. crassa spp. Leaves of all three species exhibited high Na+ content while K+, Ca++ and Mg++ contents are low. S. ruthenica accumulated 94.5 g kg-1 DW of Na+ ions while S. dendroides and S. crassa accumulated 82.1 g kg-1 DW and 71.4 g kg-1 DW Na+ ions, respectively. The increase in enzymatic activities and higher metabolic contents and lower MDA levels in Salsola spp., especially in S. ruthenica, suggested that these species could well be used for phytoremediation purposes. With moderate height and root-length, these plants have high potentials to be used as companion plants with glycophytes to reduce salt stress in moderately saline conditions.

Traditional Varieties of Caupi Submitted to Water Deficit: Physiological and Biochemical Aspects

The cowpea (Vigna unguiculata (L.) Walp) it is a leguminous widely cultivated in Northeast of Brazil. In the state of Ceara, its cultivation is performed mainly by family farms who make use of traditional varieties of good adaptation to the growing region. Thus, characterizing traditional varieties with characteristics of adaptation to regions with water shortage is essential for the production of food in the world, especially in semi-arid regions. In this sense, the objective was to evaluate the physiological and biochemical responses in three genotypes of cowpea, being two traditional varieties grown in Ceara (Sempre-Verde and Cabe&amp;ccedil;a-de-Gato) and a genotype characterized as a standard of drought tolerance (Pingo-de-Ouro-1,2) under three water regimes: irrigated, moderate deficit and severe water deficit. The parameters evaluated were: gas exchange, chlorophyll a fluorescence, photosynthetic pigments, organic solutes (proline, total carbohydrates, reducing and non-reducing carbohydrates), starch and enzyme activity (APX, G-POD, CAT and SOD). The genotype Pingo-de-Ouro-1,2 confirmed its tolerance pattern in a water deficit condition, presenting greater water potential, higher photosynthetic rate, high levels of total carbohydrates and high accumulation of proline. Among the traditional varieties, the Cabe&amp;ccedil;a-de-Gato presented superior photosynthesis to Sempre-Verde higher Electron Transport Rate (ETR), reflecting in a greater photochemical quenching (qP) and a greater accumulation of proline, indicating that this variety presents more pronounced adaptive characteristics for water restriction conditions, which is a common condition to the Brazilian semiarid.

Discerning of Rice Landraces (Oryza sativa L.) for Morpho-physiological, Antioxidant Enzyme Activity, and Molecular Markers’ Responses to Induced Salt Stress at the Seedling Stage

Salinity has been identified as key abiotic stress factor limiting rice production in many countries around the globe, including Bangladesh. In the present study, we examined the effects of salt-induced toxicity on growth of rice landraces for screening salt-tolerant genotypes by assessing morpho-physiological, biochemical, and molecular responses. Screening of 28 rice genotypes at seedling stage was performed at 12 dS m−1 salinity level in hydroponic media. Most of the rice genotypes showed an apparent reduction in growth traits, while a fewer showed less reduction under salinity stress. Euclidean clustering and heatmap based on morpho-physiological parameters dissected rice genotypes into three major clusters, viz., susceptible, moderately tolerant, and tolerant. Results of cluster analysis revealed Nonabokra, Hogla, Ghunsi, Holdegotal, Nonabokra, and Kanchon as salt-tolerant rice genotypes. These genotypes also were grouped using three microsatellite markers, viz., RM493, RM3412b, and RM140 that were closely linked to saltol QTL showed Hogla, Ghunsi, Holdegotal, Nonabokra, Kanchon, BINA dhan-8, and BINA dhan-10 as salt-tolerant genotypes considering genetic similarity in dendrogram. The positive relationships of Na+/K+ ratio with hydrogen peroxide (H2O2) and malondialdehyde (MDA), and antioxidant enzymes’ activity in the tolerant rice genotypes indicated their importance for improving salinity tolerance. The salt-tolerant landraces showed lower Na+/K+ ratio, high proline accumulation, lower H2O2 accumulation and MDA content, and higher catalase and ascorbate peroxidase activities. Higher antioxidant enzymes’ activity and lower H2O2 accumulation in tolerant genotypes indicate their abilities to fight against oxidative stress. Based on all morpho-physiological clustering, biochemical response, and molecular dendrogram, Nonabokra, Hogla, Ghunsi, Holdegotal, and Kanchon were identified as the salt-tolerant landraces. Therefore, these identified salt-tolerant landraces could be useful to improve breeding program for the development of salt-tolerant high-yielding rice cultivars in future.

Physiological introspection into differential drought tolerance in rice cultivars of North East India

Drought is a vice to world crop production, exponentially enhanced by global climate change. Rice, a basic food crop for a major chunk of world populace, is largely affected by environmental challenges such as drought, salinity and heavy metal. This study brings to limelight differential drought tolerance capacity of rice varieties indigenous to North East India, a hot bed of indica rice diversity. Initial screening of rice varieties were performed through physiological dose-dependent studies under PEG (0%, 10%, and 20% which is equal to osmotic potential values of 0.001, 0.54 and 1.09 MPa, respectively), induced drought stress for three time intervals of 1, 3 and 5 days. Hierarchical clustering of the parameters on which the cultivars were analysed revealed Tampha and KMJ 1-12-3 to be relatively more tolerant whereas Chandan and Ketaki Joha as the sensitive ones. Biochemical studies for hydrogen peroxide (H2O2), proline, lipid peroxidation (MDA), lipoxygenase (LOX), superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) were then performed on two cultivars (Tampha and Chandan) to elucidate the differential tolerance to drought, focusing on anti-oxidative response mechanism. The biochemical fingerprint showed significantly lower accumulation of H2O2 and MDA; higher accumulation of proline; and higher activity of SOD, CAT, DHAR, MDHAR and GR in the tolerant variety Tampha when compared to Chandan. In addition, alteration of chlorophyll fluorescence due to stress was also monitored to ascertain the variation in photosynthetic efficiency between the tolerant and sensitive cultivars. Tampha showed better photosynthetic activity in comparison to Chandan as quantified by measuring chlorophyll fluorescence. This manuscript thus throws new light into the drought stress response of the varieties from North East India with global implications.

Cobalt+Salt-Stressed Salvia officinalis: ROS Scavenging Capacity and Antioxidant Potency

Salvia officinalis L. (Lamiaceae) is one of the most widespread herbal species used in the food processing industry and for culinary and medicinal purposes. This work aimed to investigate changes in plant growth, water content, lipid peroxidation, H2O2, proline, and enzymes related to reactive oxygen species (ROS) detoxification including superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). Phenolic contents and antioxidant capacity values such as ferric ion reducing antioxidant power (FRAP), cupric ion reducing antioxidant capacity (CUPRAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging were studied under stress conditions of salt, cobalt and a combination of the two. No significant differences were found in relative water content and chlorophyll fluorescence under salt, cobalt and their combination. However, the osmotic potential and relative growth rate were enhanced with salt+cobalt compared to salt-treated plants. Salt and cobalt individually stimulated high antioxidant activity. High APX and GR activities were associated with the high proline accumulation in the sage plants under the combined effect of salt+cobalt. The combination decreased lipid peroxidation (TBARS), while H2O2 content was increased. This increase with the combined salt+cobalt effect may be associated with the decrease in CAT activity. Moreover, a strong correlation was found between TPC and TF content and antioxidant capacity measured via FRAP, CUPRAC and DPPH. The TPC, TF and antioxidant capacity values also increased under the salt+cobalt combination, suggesting an increase in antioxidant content in the sage leaves. Therefore, the combination of salt and cobalt improved the stress tolerance of S. officinalis.

Proteomic and physiological assessment of stress sensitive and tolerant variety of tomato treated with brassinosteroids and hydrogen peroxide under low-temperature stress

The aim of current investigation was to perform proteomics and physio-chemical studies to dissect the changes in contrasting varieties (S-22 and PKM-1) of Lycopersicon esculentum under low-temperature stress. Plant grown under variable low-temperature stress were analysed for their growth biomarkers, antioxidant enzyme activities, and other physiological parameters, which headed toward the determination of protein species responding to low-temperature and 24-epibrassinolide (EBL) concentrations. The plants grown under temperatures, 20/14, 12/7, and 10/3 °C recorded significantly lower growth biomarkers, SPAD chlorophyll, net photosynthetic rate and carbonic anhydrase activity in S-22 and PKM-1. Moreover, the combined effect of EBL and hydrogen peroxide (H2O2) significantly improved the parameters mentioned above and consecutively upgraded the different antioxidant enzymes (CAT and SOD) with higher accumulation of proline under stress and stress-free environments. Furthermore, proteomics study revealed that the maximum number of differentially expressed proteins were detected in S-22 (EBL + H2O2); while treatment with EBL + H2O2 + low temperature lost expression of 20 proteins. Overall, three proteins (O80577, Q9FJQ8, and Q9SKL2) took a substantial part in the biosynthesis of citrate cycle pathway and enhanced the growth and photosynthetic efficiency of tomato plants under low-temperature stress.

Tolerant varieties and exogenous application of nutrients can effectively manage drought stress in rice

ABSTRACTCommon abiotic stresses in rain-fed rice areas like drought can occur at any phase of crop growth and may occur periodically. Variation in intensity and severity of drought requires the use of different rice varieties and different nutrient management strategies. This study evaluated the morphological and physiological response of contrasting rice cultivars (Rajalaxmi, IR64, and Sahbhagidhan) to various nutrient combinations under water sufficience and scarce conditions. Drought stress at vegetative stage significantly reduced tiller formation, dry matter remobilization, and photosynthesis, leading to around 41.6% yield reduction. The effect of drought stress was more evident in Rajalaxmi and IR64 by a yield reduction of 57.4% and 43.2% as against only 24.3% in Sahbhagidhan. The combined application of nutrients resulted in higher proline accumulation, chlorophyll and carbohydrate concentrations, and photosynthesis and antioxidant enzymes, ultimately better tolerance to drought. This is reflected in higher values of tolerance indices and low scores of leaf drying and leaf rolling, especially for Sahbhagidhan. The combined application of P, K, Ca, Zn, and Fe resulted in 52.9, 53.3, 48.9% higher yield over P or K application. Rice drought tolerance can be managed by combining breeding of drought-tolerant high yielding varieties with the proper application of fertilizer nutrients.

Role of a cotton endoreduplication-related gene, GaTOP6B, in response to drought stress.

Cotton GaTOP6B is involved in cellular endoreduplication and a positive response to drought stress via promoting plant leaf and root growth. Drought is deemed as one of adverse conditions that could cause substantial reductions in crop yields worldwide. Since cotton exhibits a moderate-tolerant phenotype under water-deficit conditions, the plant could therefore be used to characterize potential new genes regulating drought tolerance in crop plants. In this work, GaTOP6B, encoding DNA topoisomerase VI subunit B, was identified in Asian cotton (Gossypium arboreum). Virus-induced gene silencing (VIGS) and overexpression (OE) were used to investigate the biological function of GaTOP6B in G. arboreum and Arabidopsis thaliana under drought stress. The GaTOP6B-silencing plants showed a reduced ploidy level, and displayed a compromised tolerance phenotype including lowered relative water content (RWC), decreased proline content and antioxidative enzyme activity, and an increased malondialdehyde (MDA) content under drought stress. GaTOP6B-overexpressing Arabidopsis lines, however, had increased ploidy levels, and were more tolerant to drought treatment, associated with improved RWC maintenance, higher proline accumulation, and reduced stomatal aperture under drought stress. Transcriptome analysis showed that genes involved in the processes like cell cycle, transcription and signal transduction, were substantially up-regulated in GaTOP6B-overexpressing Arabidopsis, promoting plant growth and development. More specifically, under drought stress, the genes involved in the biosynthesis of secondary metabolites such as phenylpropanoid, starch and sucrose were selectively enhanced to improve tolerance in plants. Taken together, the results demonstrated that GaTOP6B could coordinately regulate plant leaf and root growth via cellular endoreduplication, and positively respond to drought stress. Thus, GaTOP6B could be a competent candidate gene for improvement of drought tolerance in crop species.

EFICIÊNCIA DO USO DE NITROGÊNIO EM PLANTAS TRANSGÊNICAS DE TABACO COM ALTO ACÚMULO DE PROLINA

Increasing the nitrogen use efficiencyofcrop plants is a result of the improvement in the mechanisms involved in nitrogen uptake, translocation, assimilation and remobilization. In this study, tobacco plants with high accumulation of proline caused by the insertion of the VaP5CSF129Amutant gene under control of the constitutive promoter CaMV35S was used as a model to investigate the effect of overexpression of the transgene in the uptake and utilization of N. For this, an experiment was carried out in a completely randomized design, in a 2x5 factorial arrangement, with two genotypes (transgenic eventand untransformed control) and five levels of nitrogen fertilization (25, 50, 100, 200 and 400 kg N ha-¹), cultivated under greenhouse conditions. Plants were evaluated for height, number of leaves, dry mass, free proline content, nitrogencontent, total protein content and use of the applied N (efficiency of absorption -EAbs, efficiency of leaf utilization –EUtiland efficiency of plant use -EUN). The transgenic plantswith high proline accumulation were less efficient than the control plants in terms of nitrogen absorption (with lowerN levelsin root, leaves and wholeplant), which resulted in lower EAbs. There was no difference between the transgenic and control genotypesfor EUtil. However, the transgenic plants presented lower EUN in comparison tothe control plants. Our data showed thattransgenictobacco plants withhigh proline accumulation do not have potential for direct use in agricultural systems, since the alteration of the biochemical balance between the metabolisms of nitrogen and carbon did not result in plants with higher EUN.

Role of Ca2+ as protectant under heat stress by regulation of photosynthesis and membrane saturation in Anabaena PCC 7120.

The present study was aimed at understanding the effects of heat stress on selected physiological and biochemical parameters of a model cyanobacterium, Anabaena PCC 7120 in addition to amelioration strategy using exogenous Ca2+. A comparison of the cells exposed to heat stress (0-24h) in the presence or absence of Ca2+ clearly showed reduction in colony-forming ability and increase in reactive oxygen species (ROS) leading to loss in the viability of cells of Ca2+-deficient cultures. There was higher level of saturation in membrane lipids of the cells supplemented with Ca2+ along with higher accumulation of proline. Similarly, higher quantum yield (7.8-fold) in Ca2+-supplemented cultures indicated role of Ca2+ in regulation of photosynthesis. Relative electron transport rate (rETR) decreased in both the sets with the difference in the rate of decrease (slow) in Ca2+-supplemented cultures. The Ca2+-supplemented sets also maintained high levels of open reaction centers of PS II in comparison to Ca2+-deprived cells. Increase in transcripts of both subunits ((rbcL and rbcS) of RubisCO from Ca2+-supplemented Anabaena cultures pointed out the role of Ca2+ in sustenance of photosynthesis of cells via CO2 fixation, thus, playing an important role in maintaining metabolic status of the heat-stressed cyanobacterium.

Effects of exogenous proline on the physiological characteristics of Triticum aestivum L. and Lens culinaris Medik. under drought stress

Proline, which is an indicator of stress, is often considered as a good parameter for the testing of plants with good drought tolerance capacity. Thus, exogenous application of proline is a possible technique to avoid the deleterious effects of the drought on plant growth. The objectives of this study are to investigate the impact exogenous proline on the physiological behavior of two plant species, bread wheat, a monocot, and lentil, a dicot, under drought stress conditions. After several preliminary tests, optimal concentrations of exogenous proline were determined (6 mM for bread wheat and 2 mM for lentil) and both species were treated in normal and drought conditions. The results showed that water deficit affected both species leading to a reduction in growth, chlorophyll content and relative water content. Likewise, 15 % PEG-6000, which is equivalent to osmotic potential of -0.31MPa, caused a high accumulation of proline. In almost of cases we also noted a remarkable decrease in catalase (Cat), ascorbate peroxidase (APX) and gaiacol peroxidase (GPX) activities which was probably due to the oxidative stress caused by drought stress. The application of proline in stressful conditions reduced the deleterious effects caused by the stress on both species, due, particularly, to the accumulation of free endogenous proline and the increase of Cat, APX and GPX activities.