Stress Conditions In Plants Research Articles

Roka (Eruca sativa L.) Yetiştiriciliğinde Katı ve Sıvı Organik Gübre Uygulamalarının Spektral Yansıma Üzerine Etkisi

Bitkilerin spektral yansıma karakteristikleri bitki besin maddesi konsantrasyonları, stres ve diğer faktörlerin etkisi ile vejetasyon periyodu boyunca farklılık göstermektedir. Roka (Eruca sativa L.) gibi yaprağı yenen sebzelerde verimi arttırmak ve tüketicinin tercih ettiği koyu yeşil yaprak rengini kısa sürede sağlayabilmek için yoğun gübreleme yapılmaktadır. Bu çalışmada roka bitkisine artan dozlarda tabandan uygulanan katı ve sıvı organik gübre uygulamalarının, elektromanyetik spektrumun farklı dalga boyu aralığındaki enerji kullanımı üzerine etkileri araştırılmıştır. Çalışma kontrollü sera ortamında tesadüf parselleri deneme desenine göre yürütülmüştür. Denemede bitki yetişme periyodu süresince farklı dozlarda tabandan katı organik gübre (KOG) ve damlamadan sıvı organik gübre (SOG) uygulanmıştır. Bu süreçte elektromanyetik spektrumun 330-1075 nm dalga boyu aralığında el spektroradyometresi ile spektroradyometrik ölçümler gerçekleştirilmiştir. Araştırma sonucunda, her ölçümde uygulamalar ve dönemler arasında istatistiksel olarak farklılıkların olduğu tespit edilmiştir. Katı+sıvı organik gübre uygulamalarının spektral yansıma üzerinde oluşturduğu varyasyonun en fazla ve en az olduğu ölçümler sırasıyla mavi band bölgesinde; 4. ve 8. ölçümler, yeşil band bölgesinde; 5. ve 3. ölçümler, kırmızı band bölgesinde; 2. ve 8. ölçümler, yakın infrared band bölgesinde ise; 2. ve 7. ölçüm dönemlerinde tespit edilmiştir. Bu sonuçlar doğrultusunda varyasyonun en fazla ve en az olduğu ölçüm dönemlerinin bitki stres koşullarının tespit edilmesinde belirleyici olduğu sonucuna ulaşılmıştır.

Expression analysis and functional characterization of two PHT1 family phosphate transporters in ryegrass.

The phosphate transporters LpPHT1;1 and LpPHT1;4 have different roles in phosphate uptake and translocation in ryegrass under P stress condition. The phosphate transporter 1 (PHT1) family are integral membrane proteins that operate in phosphate uptake, distribution and remobilization within plants. In this study, we report on the functional characterization and expression of two PHT1 family members from ryegrass plants (Lolium perenne L.) and determine their roles in the specificity of Pi transport. The expression level of LpPHT1;4 was strongly influenced by phosphorus (P) status, being higher under P-starvation condition. In contrast, the expression level of LpPHT1;1 was not correlated with P supply. Yeast mutant complementation assays showed that LpPHT1;4 can complement the growth defect of the yeast mutant Δpho84 under Pi-deficient conditions, whereas the yeast mutant expressing LpPHT1;1 was not able to restore growth. Phylogenetic and molecular analyses indicated high sequence similarity to previously identified PHT1s from other species in the Poaceae. These results suggest that LpPHT1;1 may function as a low-affinity Pi transporter, whereas LpPHT1;4 could acts as a high-affinity Pi transporter to maintain Pi homeostasis under stress conditions in ryegrass plants. This study will form the basis for the long-term goal of improving the phosphate use efficiency of ryegrass plants.

The long non-coding RNA lncRNA973 is involved in cotton response to salt stress

BackgroundLong non-coding (lnc) RNAs are a class of functional RNA molecules greater than 200 nucleotides in length, and lncRNAs play important roles in various biological regulatory processes and response to the biotic and abiotic stresses. LncRNAs associated with salt stress in cotton have been identified through RNA sequencing, but the function of lncRNAs has not been reported. We previously identified salt stress-related lncRNAs in cotton (Gossypium spp.), and discovered the salt-related lncRNA-lncRNA973.ResultsIn this study, we identified the expression level, localization, function, and preliminary mechanism of action of lncRNA973. LncRNA973, which was localized in the nucleus, was expressed at a low level under nonstress conditions but can be significantly increased by salt treatments. Here lncRNA973 was transformed into Arabidopsis and overexpressed. Along with the increased expression compared with wild type under salt stress conditions in transgenic plants, the seed germination rate, fresh weights and root lengths of the transgenic plants increased. We also knocked down the expression of lncRNA973 using virus-induced gene silencing technology. The lncRNA973 knockdown plants wilted, and the leaves became yellowed and dropped under salt-stress conditions, indicating that the tolerance to salt stress had decreased compared with wild type. LncRNA973 may be involved in the regulation of reactive oxygen species-scavenging genes, transcription factors and genes involved in salt stress-related processes in response to cotton salt stress.ConclusionsLncRNA973 was localized in the nucleus and its expression was increased by salt treatment. The lncRNA973-overexpression lines had increased salt tolerance compared with the wild type, while the lncRNA973 knockdown plants had reduced salt tolerance. LncRNA973 regulated cotton responses to salt stress by modulating the expression of a series of salt stress-related genes. The data provides a basis for further studies on the mechanisms of lncRNA973-associated responses to salt stress in cotton.

Synergistic regulation of drought-responsive genes by transcription factor OsbZIP23 and histone modification in rice.

Thousands of differentially expressed genes (DEGs) have been identified in rice under drought stress conditions. However, the regulatory mechanism of these DEGs remains largely unclear. Here, we report an interplay between histone H3K4me3 modification and transcription factor OsbZIP23 in the regulation of a dehydrin gene cluster under drought stress conditions in rice. When the H3K4me3 modification level was increased, the dehydrin gene expression levels were increased, and the binding levels of OsbZIP23 to the promoter of the dehydrin genes were also enhanced. Conversely, the H3K4me3 modification and dehydrin gene expression levels were downregulated in the osbzip23 mutant under drought stress conditions. Our study uncovers a collaboration between transcription factor and H3K4me3 modification in the regulation of drought-responsive genes, which will help us to further understand the gene regulation mechanism under stress conditions in plants.

Histone Acetylation Dynamics Integrates Metabolic Activity to Regulate Plant Response to Stress.

Histone lysine acetylation is an essential chromatin modification for epigenetic regulation of gene expression during plant response to stress. On the other hand, enzymes involved in histone acetylation homeostasis require primary metabolites as substrates or cofactors whose levels are greatly influenced by stress and growth conditions in plants. In addition, histone lysine acylation that requires similar enzymes for deposition and removal as histone acetylation has been recently characterized in plant. Results on understanding the intrinsic relationship between histone acetylation/acylation, metabolism and stress response in plants are accumulating. In this review, we summarize recent advance in the field and propose a model of interplay between metabolism and epigenetic regulation of genes expression in plant adaptation to stress.

Abiotic and Biotic Limitations to Nodulation by Leguminous Cover Crops in South Texas

Many farms use leguminous cover crops as a nutrient management strategy to reduce their need for nitrogen fertilizer. When they are effective, leguminous cover crops are a valuable tool for sustainable nutrient management. However, the symbiotic partnership between legumes and nitrogen fixing rhizobia is vulnerable to several abiotic and biotic stressors that reduce nitrogen fixation efficiency in real world contexts. Sometimes, despite inoculation with rhizobial strains, this symbiosis fails to form. Such failure was observed in a 14-acre winter cover crop trial in the Rio Grande Valley (RGV) of Texas when three legume species produced no signs of nodulation or nitrogen fixation. This study examined the role of nitrogen, phosphorus, moisture, micronutrients, and native microbial communities in the nodulation of cowpea (Vigna unguiculata L. Walp) and assessed arbuscular mycorrhizal fungi as an intervention to improve nodulation. Results from two controlled studies confirm moisture and native microbial communities as major factors in nodulation success. Micronutrients showed mixed impacts on nodulation depending on plant stress conditions. Nitrogen and phosphorus deficiencies, however, were not likely causes, nor was mycorrhizal inoculation an effective intervention to improve nodulation. Inoculation method also had a major impact on nodulation rates. Continued research on improved inoculation practices and other ways to maximize nitrogen fixation efficiency will be required to increase successful on-farm implementation.

Combined Boron Toxicity and Salinity Stress-An Insight into Its Interaction in Plants.

The continuously changing environment has intensified the occurrence of abiotic stress conditions. Individually, boron (B) toxicity and salinity stress are well recognized as severe stress conditions for plants. However, their coexistence in arid and semi-arid agricultural regions has shown ambiguous effects on plant growth and development. Few studies have reported that combined boron toxicity and high salinity stress have more damaging effects on plant growth than individual B and salt stress, while other studies have highlighted less damaging effects of the combined stress. Hence, it is interesting to understand the positive interaction of this combined stress so that it can be effectively employed for the improvement of crops that generally show the negative effects of this combined stress. In this review, we discussed the possible processes that occur in plants in response to this combined stress condition. We highly suggest that the combined B and salinity stress condition should be considered as a novel stress condition by researchers; hence, we recommend the name “BorSal” for this combined boron toxicity and high salinity state in the soil. Membrane-bound activities, mobility of ions, water transport, pH changes, transpiration, photosynthesis, antioxidant activities, and different molecular transporters are involved in the effects of BorSal interaction in plants. The discussed mechanisms indicate that the BorSal stress state should be studied in light of the involved physiological and molecular processes that occur after B and salt interaction in plants.

Differential expression of recently duplicated PTOX genes in Glycine max during plant development and stress conditions.

Plastid terminal oxidase (PTOX) is a chloroplast enzyme that catalyzes oxidation of plastoquinol (PQH2) and reduction of molecular oxygen to water. Its function has been associated with carotenoid biosynthesis, chlororespiration and environmental stress responses in plants. In the majority of plant species, a single gene encodes the protein and little is known about events of PTOX gene duplication and their implication to plant metabolism. Previously, two putative PTOX (PTOX1 and 2) genes were identified in Glycine max, but the evolutionary origin and the specific function of each gene was not explored. Phylogenetic analyses revealed that this gene duplication occurred apparently during speciation involving the Glycine genus ancestor, an event absent in all other available plant leguminous genomes. Gene expression evaluated by RT-qPCR and RNA-seq data revealed that both PTOX genes are ubiquitously expressed in G. max tissues, but their mRNA levels varied during development and stress conditions. In development, PTOX1 was predominant in young tissues, while PTOX2 was more expressed in aged tissues. Under stress conditions, the PTOX transcripts varied according to stress severity, i.e., PTOX1 mRNA was prevalent under mild or moderate stresses while PTOX2 was predominant in drastic stresses. Despite the high identity between proteins (97%), molecular docking revealed that PTOX1 has higher affinity to substrate plastoquinol than PTOX2. Overall, our results indicate a functional relevance of this gene duplication in G. max metabolism, whereas PTOX1 could be associated with chloroplast effectiveness and PTOX2 to senescence and/or apoptosis.

Mechanisms of Silicon-Mediated Amelioration of Salt Stress in Plants.

Silicon (Si), the second most predominant element in the earth crust consists of numerous benefits to plant. Beneficial effect of Si has been apparently visible under both abiotic and biotic stress conditions in plants. Supplementation of Si improved physiology and yield on several important agricultural and horticultural crops. Salinity is one of the major abiotic stresses that affect growth and yield. The presence of high concentration of salt in growing medium causes oxidative, osmotic, and ionic stresses to plants. In extreme conditions salinity affects soil, ground water, and limits agricultural production. Si ameliorates salt stress in several plants. The Si mediated stress mitigation involves various regulatory mechanisms such as photosynthesis, detoxification of harmful reactive oxygen species using antioxidant and non-antioxidants, and proper nutrient management. In the present review, Si mediated alleviation of salinity stress in plants through the regulation of photosynthesis, root developmental changes, redox homeostasis equilibrium, and regulation of nutrients have been dealt in detail.

Genome-wide mining of respiratory burst homologs and its expression in response to biotic and abiotic stresses in Triticum aestivum.

Membrane-bound NADPH oxidases (Nicotinamide adenine ainucleotide phosphate oxidase) also called respiratory burst oxidase homologs (Rboh) play an essential role in ROS production under normal as well as environmental stress conditions in plants. To identify and study respiratory burst homologs (Rboh) from the wheat genome as well as characterize their role in various biological and molecular processes along with expression in response to biotic and abiotic stresses. The Rboh homologs in the wheat genome were predicted based on data processing, alignment of sequences and phylogenetic analysis of sequences in numerous plant species and wheat. The conserved motifs were known followed by domain design study. The 3-D structure prediction and similarity modeling were administered for NADPH enzyme domain. Gene ontology and a functional study were done in addition to expression analysis of Triticum aestivum respiratory burst oxidase (TaRboh) gene family in response to biotic as well as abiotic stress. Phylogenetic analysis of Rboh gene family members among seven plant species including wheat, classified the family into four subfamilies. Rboh genes are mainly involved in various biological processes such as Response to oxidative stress, Superoxide anion generation, Hydrogen peroxide biosynthetic process. Among the molecular functions, calcium ion binding, peroxidase activity, oxidoreductase activity, superoxide-generating NADPH oxidase activity are essential. Enzyme annotation of the family and superfamily revealed that it encodes to five structural clusters and coding to enzymes NAD(P)H oxidase (H2O2-forming) (EC:1.6.3.1), Ferric-chelate reductase (NADH) (EC: 1.16.1.7), Peroxidase (EC: 1.11.1.7), Ribose-phosphate diphosphokinase (EC: 2.7.6.1). The enzymes contain six membrane-spanning domains, two hemes, and conserved motifs associated with NADPH, EF-hand and FAD binding. The outcomes additionally reflect a distinct role of this enzyme in different molecular functions which are responsible for the stress signaling. Further, the transcripts of TaRboh found expressed in various plant parts such as stem, leaves, spike, seed, and roots. We also observed expression of these gene family members under drought/combination of drought + heat and important wheat pathogens such as Puccinia striformis, Blumeria graminis f.sp. tritici, Fusarium graminiarum, F. pseudograminiarum, and Zymoseptoria tritici. The investigation demonstrated that identified respiratory burst homologs (Rboh) in T. aestivum were involved in pathogen activated ROS production and have regulatory functions in cell death and defense responses.

Perspective on Alternative Splicing and Proteome Complexity in Plants.

Alternative splicing (AS) generates multiple transcripts from the same gene, however, AS contribution to proteome complexity remains elusive in plants. AS is prevalent under stress conditions in plants, but it is counterintuitive why plants would invest in protein synthesis under declining energy supply. We propose that plants employ AS not only to potentially increasing proteomic complexity, but also to buffer against the stress-responsive transcriptome to reduce the metabolic cost of translating all AS transcripts. To maximise efficiency under stress, plants may make fewer proteins with disordered domains via AS to diversify substrate specificity and maintain sufficient regulatory capacity. Furthermore, we suggest that chromatin state-dependent AS engenders short/long-term stress memory to mediate reproducible transcriptional response in the future.

Aromatic amino acids biosynthesis genes identification and expression analysis under salt and drought stresses in Solanum lycopersicum L.

Aromatic amino acids (AAA), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp), are essential molecules in the plant metabolism. In this study, three AAA biosynthesis genes, chorismate synthase (CS), chorismate mutase (CM) and anthranilate synthase (AS), were identified in genome-wide scale in tomato (Solanum lycopersicum) genome. Also, bioinformatics analyses including sequence and phylogenetic analyses, predicted microRNAs targeting, digital expression and co-expression analyses and seconder and tertiary structure analyses of AAA proteins were performed. The expressions of AAA genes under drought and salt stresses were evaluated using Real Time-quantitative PCR (RT-qPCR). The promotor sequence analyses of the genes showed the presence of diverse cis-regularity elements, including light responsive, hormone responsiveness, heat stress responsiveness and elicitor-responsive elements. Based on the digital expression data, CS1 is more consistently expressed over CM1 and ASA1 through developmental stages in tomato. Co-expression network analyses revealed complex interactions between AAA genes and genes in other metabolic pathways. The expressions of AAA genes fluctuated between 0.93–2.23 fold under drought and salt stresses. Over all, it can be proposed that data obtained from this study could contribute to identification and functions of AAA genes under abiotic stress conditions for plants, particularly tomato.

Actinobacteria for sustainable agriculture

Actinobacteria is a phylum and class of Gram-positive bacteria. The phylum Actinobacteria are classified into six classes namely Acidimicrobiia, Actinobacteria, Coriobacteriia, Nitriliruptoria, Rubrobacteria and Thermoleophilia. Members of phylum Actinobacteria are ubiquitous in nature. Actinobacteria can be utilized as biofertilizers for sustainable agriculture as they can enhance plant growth and soil health though different plant growth promoting attributes such as solubilization of phosphorus, potassium and zinc, production of Fe-chelating compounds, phytohormones hormones such indole acetic acids, cytokinin, and gibberellins as well as by biological nitrogen fixation. The Actinobacteria also plays an important role in mitigation of different abiotic stress conditions in plants. The members of phylum Actinobacteria such as Actinomyces, Arthrobacter, Bifidobacterium, Cellulomonas, Clavibacter, Corynebacterium, Frankia, Microbacterium, Micrococcus, Mycobacterium, Nocardia, Propionibacterium, Pseudonocardia, Rhodococcus, Sanguibacter and Streptomyces exhibited the multifarious plant growth promoting attributes and could be used as biofertilizers for crops growing under natural as well as under the abiotic stress conditions for plant growth and soil health for sustainable agriculture.

Overexpression of a maize SUMO conjugating enzyme gene (ZmSCE1e) increases Sumoylation levels and enhances salt and drought tolerance in transgenic tobacco

As an essential regulatory process of post-translational modifications, Sumoylation has been shown to play a central role in stress responses in higher plants. However, the mechanisms underlying the involvement of the Sumoylation in stress responses in crops are largely unknown. In this study, a putative SUMO conjugating enzyme ortholog from Zea mays (ZmSCE1e) was isolated. Sequence alignments and phylogenetic analysis showed that ZmSCE1e possesses a central active domain similar to known SCE1 proteins, but is the cereal-specific isoform.The transcript levels of ZmSCE1e were markedly up-regulated by salt or drought stress. Over-expression of ZmSCE1e in tobacco plants increased levels of SUMO conjugates and enhanced their tolerances to salt and drought stresses. ZmSCE1e-transgenic plants showed higher activities of key antioxidant enzymes but lower hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulations under salt or drought stress. Furthermore, expression of several stress defense genes was significantly elevated as revealed by qPCR in the ZmSCE1e-transgenic lines. Together, these data have demonstrated that ZmSCE1e improved salt and drought tolerance likely by modulating Sumoylation levels, antioxidant capability, and stress defense gene expression in transgenic plants. This study may facilitate our understanding of the biological roles of SCE-mediated Sumoylation under stress conditions in higher plants and accelerate genetic improvement of crop plants tolerant to environmental stresses.

Triterpenoid gene expression and phytochemical content in Iranian licorice under salinity stress.

Licorice is a well-known medicinal plant, containing various secondary metabolites of triterpenoid and phenolic families. The aim of this study is to evaluate the effect of salinity stress on the expression of key genes involved in the biosynthetic pathway of triterpenoids such as glycyrrhizin, betulinic acid, soyasaponins, and phytosterols in licorice root, as well as providing a phonemic platform to characterize antioxidant properties, glycyrrhizin, and total phenolic content. This study also includes measuring the gene expression level and glycyrrhizin content in leaves and roots of control plants. The studied genes included squalene synthase (SQS1 and SQS2), β-amyrin synthase (bAS), lupeol synthase (LUS), cycloartenol synthase (CAS), β-amyrin 11-oxidase (CYP88D6), and β-amyrin 24-hydroxylase (CYP93E6). Our results revealed that all of the mentioned genes were upregulated following the stress condition with different transcription rates. The highest increase (12-fold) was observed for the expression of the LUS gene, which is related to the betulinic acid pathway. Also, the highest content of glycyrrhizin was observed at 72h post-treatment, which was consistent with the upregulated transcription levels of the glycyrrhizin pathway genes especially SQS1 and CYP88D6 at the same time. Correlation and stepwise regression analysis proved the key role of SQS1 gene in the biosynthetic pathway of glycyrrhizin. Antioxidant activity and phenolic content also were increased following stress condition. A comparison between the expression levels of SQS1 and other genes involved in the production of glycyrrhizin, phytosterols, and soyasaponins revealed a similar transcription trend, which shows the gene expression in the roots was significantly higher than the leaves. In contrast, SQS2 and LUS genes displayed a higher expression in leaf tissues. The genes related to betulinic acid biosynthetic pathway exhibited an expression rate different from other triterpenoid pathway genes, which could be observed in the leaves and roots of control plants and the roots of salt-treated plants. Furthermore, results showed that these two SQS genes have different expression rates due to different plant tissues (roots and leaves) and stress conditions. Importantly, in contrast to previous reports, we detected the glycyrrhizin in leaf tissues. This result may indicate the presence of a different genetic background in native Iranian licorice germplasm.

Evaluating plant stress conditions in paprika by comparing internal electrical conductivity, photosynthetic response, and sap flow

A non-destructive analytical method to measure plant internal electrical conductivity (ECp) was developed to monitor plant responses to changes in environmental conditions. However, the relationship between ECp and plant physiological responses has not yet been established. The objective of the study was to evaluate the relationships among ECp, photosynthetic responses, and sap flow in paprika to monitor ECp in relation to changes in environmental conditions. High ECp levels were related to high photosynthetic rate, stomatal conductance, and transpiration rate. Sap flow in the plant was also associated with ECp with a correlation coefficient of 0.606. However, the sap flow reflected only water flux, while ECp was determined by both water and ion content in stems of paprika. The ECp was predicted using environmental factors including temperature, irradiation, and relative humidity. A comparison of measured and predicted ECps could be used to detect unusual cultivation conditions for paprika such as drought and high temperature. Plant responses to water shortage were reflected by lower ECp compared to the predicted value.

The Salt-Stress Response of the Transgenic Plum Line J8-1 and Its Interaction with the Salicylic Acid Biosynthetic Pathway from Mandelonitrile.

Salinity is considered as one of the most important abiotic challenges that affect crop productivity. Plant hormones, including salicylic acid (SA), are key factors in the defence signalling output triggered during plant responses against environmental stresses. We have previously reported in peach a new SA biosynthetic pathway from mandelonitrile (MD), the molecule at the hub of the cyanogenic glucoside turnover in Prunus sp. In this work, we have studied whether this new SA biosynthetic pathway is also present in plum and the possible role this pathway plays in plant plasticity under salinity, focusing on the transgenic plum line J8-1, which displays stress tolerance via an enhanced antioxidant capacity. The SA biosynthesis from MD in non-transgenic and J8-1 micropropagated plum shoots was studied by metabolomics. Then the response of J8-1 to salt stress in presence of MD or Phe (MD precursor) was assayed by measuring: chlorophyll content and fluorescence parameters, stress related hormones, levels of non-enzymatic antioxidants, the expression of two genes coding redox-related proteins, and the content of soluble nutrients. The results from in vitro assays suggest that the SA synthesis from the MD pathway demonstrated in peach is not clearly present in plum, at least under the tested conditions. Nevertheless, in J8-1 NaCl-stressed seedlings, an increase in SA was recorded as a result of the MD treatment, suggesting that MD could be involved in the SA biosynthesis under NaCl stress conditions in plum plants. We have also shown that the plum line J8-1 was tolerant to NaCl under greenhouse conditions, and this response was quite similar in MD-treated plants. Nevertheless, the MD treatment produced an increase in SA, jasmonic acid (JA) and reduced ascorbate (ASC) contents, as well as in the coefficient of non-photochemical quenching (qN) and the gene expression of Non-Expressor of Pathogenesis-Related 1 (NPR1) and thioredoxin H (TrxH) under salinity conditions. This response suggested a crosstalk between different signalling pathways (NPR1/Trx and SA/JA) leading to salinity tolerance in the transgenic plum line J8-1.

Selection of emission detection ranges for the laser method of plant stress revealing at a fluorescence excitation wavelength of 355 nm

The paper considers the development of a laser fluorescent method for the detection of plant stress conditions. The results of experimental studies of laser-induced fluorescence spectra of plants in normal and various stress conditions caused by various pollutants in the soil are presented for the laser wavelength of fluorescence excitation of 355 nm. A comparative analysis of various options has been carried out for choosing the spectral ranges of laser-induced fluorescent radiation plant registration. It is shown that for the task of monitoring the state of plants, the most effective (from the point of view of reliability of correct detection of stress conditions) ranges of fluorescent radiation registration are spectral ranges with central wavelengths of 685 and 740 nm.

Proline Accumulation and its Defensive Role Under Diverse Stress Condition in Plants: An Overview

Proline Accumulation and its Defensive Role Under Diverse Stress Condition in Plants: An Overview

Metabolic process of raffinose family oligosaccharides during cold stress and recovery in cucumber leaves

Raffinose family oligosaccharides (RFOs) accumulate under stress conditions in many plants and have been suggested to act as stress protectants. To elucidate the metabolic process of RFOs under cold stress, levels of RFOs, and related carbohydrates, the expression and activities of main metabolic enzymes and their subcellular compartments were investigated during low-temperature treatment and during the recovery period in cucumber leaves. Cold stress induced the accumulation of stachyose in vacuoles, galactinol in vacuoles and cytosol, and sucrose and raffinose in vacuoles, cytosol, and chloroplasts. After cold stress removal, levels of these sugars decreased gradually in the respective compartments. Among four galactinol synthase genes (CsGS), CsGS1 was not affected by cold stress, while the other three CsGSs were up-regulated by low temperature. RNA levels of acid-α-galactosidase (GAL) 3 and alkaline-α-galactosidase (AGA) 2 and 3, and the activities of GAL and AGA, were up-regulated after cold stress removal. GAL3 protein and GAL activity were exclusively located in vacuoles, whereas AGA2 and AGA 3 proteins were found in cytosol and chloroplasts, respectively. The results indicate that RFOs, which accumulated during cold stress in different subcellular compartments in cucumber leaves, could be catabolized in situ by different galactosidases after stress removal.