Enhancing rice growth and yield with weed endophytic bacteria Alcaligenes faecalis and Metabacillus indicus under reduced chemical fertilization.

Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting effects of endophytic bacteria have been extensively studied, the impact of weed endophytes remains less explored. In this study, we aimed to isolate endophytic bacteria from native weeds and assess their plant growth-promoting abilities in rice under varying chemical fertilization. The evaluation encompassed measurements of mineral phosphate and potash solubilization, as well as indole-3-acetic acid (IAA) production activity by the selected isolates. Two promising strains, tentatively identified as Alcaligenes faecalis (BTCP01) from Eleusine indica (Goose grass) and Metabacillus indicus (BTDR03) from Cynodon dactylon (Bermuda grass) based on 16S rRNA gene phylogeny, exhibited noteworthy phosphate and potassium solubilization activity, respectively. BTCP01 demonstrated superior phosphate solubilizing activity, while BTDR03 exhibited the highest potassium (K) solubilizing activity. Both isolates synthesized IAA in the presence of L-tryptophan, with the detection of nifH and ipdC genes in their genomes. Application of isolates BTCP01 and BTDR03 through root dipping and spraying at the flowering stage significantly enhanced the agronomic performance of rice variety CV. BRRI dhan29. Notably, combining both strains with 50% of recommended N, P, and K fertilizer doses led to a substantial increase in rice grain yields compared to control plants receiving 100% of recommended doses. Taken together, our results indicate that weed endophytic bacterial strains BTCP01 and BTDR03 hold promise as biofertilizers, potentially reducing the dependency on chemical fertilizers by up to 50%, thereby fostering sustainable rice production.

Genetic control of root architectural traits under drought stress in spring barley (Hordeum vulgare L.).

Root architectural traits play pivotal roles in plant adaptation to drought stress, and hence they are considered promising targets in breeding programs. Here, we phenotyped eight root architecture traits in response to well-watered and drought stress conditions in 200 spring barley (Hordeum vulgare L.) inbred lines over two consecutive field seasons. Root architecture traits were less developed under drought in both seasons when compared with control treatments. Genetic variation in root architectural traits was dissected employing a genome-wide association study (GWAS) coupled with linkage disequilibrium mapping. GWAS uncovered a total of 186 significant single nucleotide polymorphism-trait associations for eight root traits under control, drought, and drought-related indices. Of these, a few loci for root traits were detected on chromosomes 3 and 5, which co-located with QTL identified in previous studies. Interestingly, 13 loci showed simultaneou associations with multiple root traits under drought and drought-related indices. These loci harbored candidate genes, which included a wide range of drought-responsive components such as transcription factors, binding proteins, protein kinases, nutrient and ion transporters, and stress signaling factors. For instance, two candidate genes, HORVU7Hr3G0713160 and HORVU6H r3G0626550, are orthologous to AtACX3 and AtVAMPs, which have reported functions in root length-mediated drought tolerance and as a key protein in abiotic stress tolerance, respectively. Interestingly, one of these loci underlying a high-confidence candidate gene NEW ENHANCER OF ROOT DWARFISM1 (NERD1) showed involvement with root development. An allelic variation of this locus in non-coding region was significantly associated with increased root length under drought. Collectively, these results offer promising multi-trait affecting loci and candidate genes underlying root phenotypic responses to drought stress, which may provide valuable resources for genetic improvement of drought tolerance in barley.

Genome-wide dissection and haplotype analysis identified candidate loci for nitrogen use efficiency under drought conditions in winter wheat.

Climate change causes extreme conditions like prolonged drought, which results in yield reductions due to its effects on nutrient balances such as nitrogen uptake and utilization by plants. Nitrogen (N) is a crucial nutrient element for plant growth and productivity. Understanding the mechanistic basis of nitrogen use efficiency (NUE) under drought conditions is essential to improve wheat (Triticum aestivum L.) yield. Here, we evaluated the genetic variation of NUE-related traits and photosynthesis response in a diversity panel of 200 wheat genotypes under drought and nitrogen stress conditions to uncover the inherent genetic variation and identify quantitative trait loci (QTLs) underlying these traits. The results revealed significant genetic variations among the genotypes in response to drought stress and nitrogen deprivation. Drought impacted plant performance more than N deprivation due to its effect on water and nutrient uptake. GWAS identified a total of 27 QTLs with a significant main effect on the drought-related traits, while 10 QTLs were strongly associated with the NUE traits. Haplotype analysis revealed two different haplotype blocks within the associated region on chromosomes 1B and 5A. The two haplotypes showed contrasting effects on N uptake and use efficiency traits. The in silico and transcript analyses implicated candidate gene coding for cold shock protein. This gene was the most highly expressed gene under several stress conditions, including drought stress. Upon validation, these QTLs on 1B and 5A could be used as a diagnostic marker for NUE and drought tolerance screening in wheat.

Exploring the Phenotypic and Genetic Variabilities in Yield and Yield-Related Traits of the Diallel-Crossed F5 Population of Aus Rice.

Rice (Oryza sativa) is a major crop and a main food for a major part of the global population. Rice species have derived from divergent agro-climatic regions, and thus, the local germplasm has a large genetic diversity. This study investigated the relationship between phenotypic and genetic variabilities of yield and yield-associated traits in Aus rice to identify short-duration, high-yielding genotypes. Targeting this issue, a field experiment was carried out to evaluate the performance of 51 Aus rice genotypes, including 50 accessions in F5 generation and one short-duration check variety BINAdhan-19. The genotypes exhibited a large and significant variation in yield and its associated traits, as evidenced by a wide range of their coefficient of variance. The investigated traits, including days to maturity (DM), plant height (PH), panicle length (PL) and 1000-grain weight (TW) exhibited a greater genotypic coefficient of variation than the environmental coefficient of variation. In addition, the high broad-sense heritability of DM, PH, PL and TW traits suggests that the genetic factors significantly influence the observed variations in these traits among the F5 Aus rice accessions. This study also revealed that the grain yield per hill (GY) displayed a significant positive correlation with PL, number of filled grains per panicle (FG) and TW at both genotype and phenotype levels. According to the hierarchical and K-means cluster analyses, the accessions BU-R-ACC-02, BU-R-ACC-08 and R2-36-3-1-1 have shorter DM and relatively higher GY than other Aus rice accessions. These three accessions could be employed in the ongoing and future breeding programs for the improvement of short-duration and high-yielding rice cultivars.

Convergently selected NPF2.12 coordinates root growth and nitrogen use efficiency in wheat and barley.

Understanding the genetic and molecular function of nitrate sensing and acquisition across crop species will accelerate breeding of cultivars with improved nitrogen use efficiency (NUE). Here, we performed a genome-wide scan using wheat and barley accessions characterized under low and high N inputs that uncovered the NPF2.12 gene, encoding a homolog of the Arabidopsis nitrate transceptor NRT1.6 and other low-affinity nitrate transporters that belong to the MAJOR FACILITATOR SUPERFAMILY. Next, it is shown that variations in the NPF2.12 promoter correlated with altered NPF2.12 transcript levels where decreased gene expression was measured under low nitrate availability. Multiple field trials revealed a significantly enhanced N content in leaves and grains and NUE in the presence of the elite allele TaNPF2.12TT grown under low N conditions. Furthermore, the nitrate reductase encoding gene NIA1 was up-regulated in npf2.12 mutant upon low nitrate concentrations, thereby resulting in elevated levels of nitric oxide (NO) production. This increase in NO correlated with the higher root growth, nitrate uptake, and N translocation observed in the mutant when compared to wild-type. The presented data indicate that the elite haplotype alleles of NPF2.12 are convergently selected in wheat and barley that by inactivation indirectly contribute to root growth and NUE by activating NO signaling under low nitrate conditions.

Pinpointing genomic loci for drought-induced proline and hydrogen peroxide accumulation in bread wheat under field conditions.

BACKGROUND: Proline (Pro) and hydrogen peroxide (H2O2) play a critical role in plants during drought adaptation. Genetic mapping for drought-induced Pro and H2O2 production under field conditions is very limited in crop plants since their phenotyping with large populations is labor-intensive. A genome-wide association study (GWAS) of a diversity panel comprised of 184 bread wheat cultivars grown in natural field (control) and rain-out shelter (drought) environments was performed to identify candidate loci and genes regulating Pro and H2O2 accumulation induced by drought. RESULTS: The GWAS identified top significant marker-trait associations (MTAs) on 1A and 2A chromosomes, respectively for Pro and H2O2 in response to drought. Similarly, MTAs for stress tolerance index (STI) of Pro and H2O2 were identified on 5B and 1B chromosomes, respectively. Total 143 significant MTAs were identified including 36 and 71 were linked to drought and 2 and 34 were linked to STI for Pro and H2O2, respectively. Next, linkage disequilibrium analysis revealed minor alleles of significant single-markers and haplotypes were associated with higher Pro and H2O2 accumulation under drought. Several putative candidate genes for Pro and H2O2 content encode proteins with kinase, transporter or protein-binding activities. CONCLUSIONS: The identified genetic factors associated with Pro and H2O2 biosynthesis underlying drought adaptation lay a fundamental basis for functional studies and future marker-assisted breeding programs.

Validation of a QTL on Chromosome 1DS Showing a Major Effect on Salt Tolerance in Winter Wheat.

Salt stress is one the most destructive abiotic stressors, causing yield losses in wheat worldwide. A prerequisite for improving salt tolerance is the identification of traits for screening genotypes and uncovering causative genes. Two populations of F3 lines developed from crosses between sensitive and tolerant parents were tested for salt tolerance at the seedling stage. Based on their response, the offspring were classified as salt sensitive and tolerant. Under saline conditions, tolerant genotypes showed lower Na+ and proline content but higher K+, higher chlorophyll content, higher K+/Na+ ratio, higher PSII activity levels, and higher photochemical efficiency, and were selected for further molecular analysis. Five stress responsive QTL identified in a previous study were validated in the populations. A QTL on the short arm of chromosome 1D showed large allelic effects in several salt tolerant related traits. An expression analysis of associated candidate genes showed that TraesCS1D02G052200 and TraesCS5B02G368800 had the highest expression in most tissues. Furthermore, qRT-PCR expression analysis revealed that ZIP-7 had higher differential expressions under saline conditions compared to KefC, AtABC8 and 6-SFT. This study provides information on the genetic and molecular basis of salt tolerance that could be useful in development of salt-tolerant wheat varieties.

Natural selection under conventional and organic cropping systems affect root architecture in spring barley.

A beneficial root system is crucial for efficient nutrient uptake and stress tolerance. Therefore, evaluating the root system variation for breeding crop plants towards stress adaptation is critically important. Here, we phenotyped root architectural traits of naturally adapted populations from organic and conventional cropping systems under hydroponic and field trails. Long-term natural selection under these two cropping systems resulted in a microevolution of root morphological and anatomical traits. Barley lines developed under an organic system possessed longer roots with narrow root angle, larger surface area, increased root mass density, and a thinner root diameter with an increased number of metaxylem vessels. In contrast, lines adapted to the conventional system tend to have a shorter and wider root system with a larger root volume with a thicker diameter but fewer metaxylem vessels. Allometry analysis established a relationship between root traits and plant size among barley genotypes, which specifies that root angle could be a good candidate among studied root traits to determine root-borne shoot architecture. Further, multivariate analyses showed a strong tendency towards increased variability of the organically adapted population's root morphological and anatomical traits. The genotyping of ancestor populations validated the observations made in these experiments. Collectively, this results indicate significant differences in root phenotypes between conventional and organic populations, which could be useful in comparative genomics and breeding.

Functional dairy products as a source of bioactive peptides and probiotics: current trends and future prospectives.

Milk is an incredibly healthy food world-wide. However, the 'lactase deficient' individuals cannot digest milk's carbohydrate lactose. A large part of the world population is depriving of highly beneficial milk proteins like casein, lactoalbumin, lactoglobulin, etc. due to lactose intolerance. Production of functional foods and bioactive peptides from milk with natural antioxidants and the addition of probiotics could be the best alternative to extend the use of milk functionalities. Among different probiotics, the lactic acid bacteria (LAB) like Lactobacillus delbrueckii sub sp. bulgaricus, Streptococcus thermophilus and some species of Bifidobacteria and their metabolites (paraprobiotics and postbiotics) have been given more preference to add in milk-derived functional foods. These species are generally considered as heat-tolerant, highly proteolytic, and peptidolytic towards milk proteins and they liberate smaller molecules of bioactive peptides during fermentation and other processes that stimulate the enzyme lactase to help people in digestion of milk carbohydrate lactose. Moreover, the incorporation of natural antioxidants in yoghurt and other dairy products prevents the rancidity of milk fat. The level of bioactive peptides produced in milk-derived functional foods can be determined by capillary zone electrophoresis, mass spectrometry, fractionation, and other modern assessment techniques. Commercial production of functional probiotic products with bioactive peptides could significantly contribute to reduce milk spoilage, enhance health benefits as well as the growth of the agro-processing industry.

Adaptive Mechanisms of Halophytes and Their Potential in Improving Salinity Tolerance in Plants.

Soil salinization, which is aggravated by climate change and inappropriate anthropogenic activities, has emerged as a serious environmental problem, threatening sustainable agriculture and future food security. Although there has been considerable progress in developing crop varieties by introducing salt tolerance-associated traits, most crop cultivars grown in saline soils still exhibit a decline in yield, necessitating the search for alternatives. Halophytes, with their intrinsic salt tolerance characteristics, are known to have great potential in rehabilitating salt-contaminated soils to support plant growth in saline soils by employing various strategies, including phytoremediation. In addition, the recent identification and characterization of salt tolerance-related genes encoding signaling components from halophytes, which are naturally grown under high salinity, have paved the way for the development of transgenic crops with improved salt tolerance. In this review, we aim to provide a comprehensive update on salinity-induced negative effects on soils and plants, including alterations of physicochemical properties in soils, and changes in physiological and biochemical processes and ion disparities in plants. We also review the physiological and biochemical adaptation strategies that help halophytes grow and survive in salinity-affected areas. Furthermore, we illustrate the halophyte-mediated phytoremediation process in salinity-affected areas, as well as their potential impacts on soil properties. Importantly, based on the recent findings on salt tolerance mechanisms in halophytes, we also comprehensively discuss the potential of improving salt tolerance in crop plants by introducing candidate genes related to antiporters, ion transporters, antioxidants, and defense proteins from halophytes for conserving sustainable agriculture in salinity-prone areas.

New drought-adaptive loci underlying candidate genes on wheat chromosome 4B with improved photosynthesis and yield responses.

Flag leaf serves as an essential source of assimilates during grain filling, thereby contributing to grain yield up to 48%. Thus, high-throughput phenotyping of flag leaves is crucial to determine their physiological and genetic basis of yield formation and drought adaptation. Here, we utilized 200 wheat cultivars to identify drought-adaptive loci underlying candidate genes associated with flag leaf biomass and photosynthesis-related traits using a genome-wide association study (GWAS). GWAS revealed 21 significant marker-trait associations for key photosynthetic traits in response to drought stress. Analysis of linkage disequilibrium (LD) in these SNPs intervals discovered 103 significant SNPs that established distinct LD blocks containing a total of 382 candidate genes putatively involved in physiological processes, including photosynthesis and water responses. Further, in silico transcript analysis identified two candidate genes in locus AX-580365925 on chromosome 4B, those were found to be highly expressed under drought and associated with proton-transporting ATP synthase activity and stress response pathways. Accordingly, we identified significant allelic haplotype differences on this same locus. The tolerant haplotype (higher chlorophyll content under drought) representing major allele was more abundant and stably increased photosynthetic efficiency and yield under drought scenarios. Collectively, this study offers new adaptive loci and beneficial alleles to reshape the flag leaf physiological and associated photosynthetic components for better yield and sustainability to water-deficit stress.

Understanding the roles of osmolytes for acclimatizing plants to changing environment: a review of potential mechanism.

Abiotic stresses are significant environmental issues that restrict plant growth, productivity, and survival while also posing a threat to global food production and security. Plants produce compatible solutes known as osmolytes to adapt themselves in such changing environment. Osmolytes contribute to homeostasis maintenance, provide the driving gradient for water uptake, maintain cell turgor by osmotic adjustment, and redox metabolism to remove excess level of reactive oxygen species (ROS) and reestablish the cellular redox balance as well as protect cellular machinery from osmotic stress and oxidative damage. Perceiving the mechanisms how plants interpret environmental signals and transmit them to cellular machinery to activate adaptive responses is important for crop improvement programs to get stress-tolerant varieties. A large number of studies conducted in the last few decades have shown that osmolytes accumulate in plants and have strong associations with abiotic stress tolerance. Production of abundant osmolytes is needed for tolerance in many plant species. In addition, transgenic plants overexpressing genes for different osmolytes showed enhanced tolerance to various abiotic stresses. Many important aspects of their mechanisms of action are yet to be largely identified, especially regarding the relevance and relative contribution of specific osmolytes to the stress tolerance of a given species. Therefore, more efforts and resources should be invested in the study of the abiotic stress responses of plants in their natural habitats. The present review focuses on the possible roles and mechanisms of osmolytes and their association toward abiotic stress tolerance in plants. This review would help the readers in learning more about osmolytes and how they behave in changing environments as well as getting an idea of how this knowledge could be applied to develop stress tolerance in plants.

Physiological and Biochemical Dissection Reveals a Trade-off Between Antioxidant Capacity and Heat Tolerance in Bread Wheat (Triticum aestivum L.).

Heat stress alters photosynthetic components and the antioxidant scavenging system, negatively affecting plant growth and development. Plants overcome heat stress damage through an integrated network involving enzymatic and non-enzymatic antioxidants. This study aimed to assess physiological and biochemical responses in contrasting thermo-tolerant wheat varieties exposed to 25 °C (control) and 35 °C (heat stress), during the seedling stage. Our results revealed a substantial decrease in the photosynthetic pigments, carotenoids, anthocyanin content, and increased membrane injury index, malondialdehyde, methylglyoxal (MG), H2O2 contents and lipoxygenase activity compared to non-stress wheat seedlings. The heat-tolerant variety BARI Gom 26 ("BG26") maintained higher cellular homeostasis compared to the heat susceptible variety Pavon 76 ("Pavon"), perpetuated by higher accumulation of proline, glycine betaine, ascorbate-glutathione cycle associated enzymes, reduced glutathione and ascorbate concentration in plant cells. Significantly lower levels of MG detoxification and antioxidant activities and ascorbate-glutathione cycle-related enzymatic activities lead to increased susceptibility in variety "Pavon". Hierarchical clustering and principal component analysis revealed that variety "BG26" possess a combination of biochemical responses tailoring antioxidant activities that induced a higher level of tolerance. Taken together, our results provide a pipeline for establishing a trade-off between antioxidant capacity and heat tolerance to facilitate functional genomics and translational research to unravel underlying mechanisms to better adapt wheat to heat stress.

Glutathione improves rice tolerance to submergence: insights into its physiological and biochemical mechanisms.

Complete submergence (Sub) imposes detrimental effects on growth and survival of crop plants, including rice. Here, we investigated the beneficial effects of reduced glutathione (GSH) in mitigating Sub-induced adverse effects in two high-yielding rice cultivars BRRI dhan29 and dhan52. Both cultivars experienced growth defects, severe yellowing, necrosis and chlorosis, when they were completely immersed in water for 14 days. The poor growth performance of these cultivars was linked to biomass reduction, decreased levels of photosynthetic pigments and proline, increased levels of H2O2 and malondialdehyde, and declined activities of enzymatic antioxidants like superoxide dismutase, ascorbate peroxidase, peroxidase, catalase, glutathione peroxidase and glutathione S-transferase. Pretreatment with exogenous GSH led to significant growth restoration in both cultivars exposed to Sub. The elevated Sub-tolerance promoted by GSH could partly be attributed to increased levels of chlorophylls, carotenoids, soluble proteins and proline. Exogenous GSH also mitigated Sub-induced oxidative damage, as evidenced from reduced levels of H2O2 and malondialdehyde in accordance with the increased activities of antioxidant enzymes. Results revealed that dhan52 was more tolerant to Sub-stress than dhan29, and GSH successfully rescued both cultivars from the damage of Sub-stress. Collectively, our findings provided an insight into the GSH-mediated active recovery of rice from Sub-stress, thereby suggesting that external supply of GSH may be an effective strategy to mitigate the adverse effects of Sub in rice.

Genetics and genomics of root system variation in adaptation to drought stress in cereal crops.

Cereals are important crops worldwide that help meet food demands and nutritional needs. In recent years, cereal production has been challenged globally by frequent droughts and hot spells. A plant's root is the most relevant organ for the plant adaptation to stress conditions, playing pivotal roles in anchorage and the acquisition of soil-based resources. Thus, dissecting root system variations and trait selection for enhancing yield and sustainability under drought stress conditions should aid in future global food security. This review highlights the variations in root system attributes and their interplay with shoot architecture features to face water scarcity and maintain thus yield of major cereal crops. Further, we compile the root-related drought responsive quantitative trait loci/genes in cereal crops including their interspecies relationships using microsynteny to facilitate comparative genomic analyses. We then discuss the potential of an integrated strategy combining genomics and phenomics at genetic and epigenetic levels to explore natural genetic diversity as a basis for knowledge-based genome editing. Finally, we present an outline to establish innovative breeding leads for the rapid and optimized selection of root traits necessary to develop resilient crop varieties.

Tackling the COVID-19 pandemic: The Bangladesh perspective.

An outbreak of a COVID-19 pandemic disease, caused by a novel coronavirus SARS-CoV-2, has posed a serious threat to global human health. Bangladesh has also come under the attack of this viral disease. Here, we aimed to describe the responses of Bangladesh to tackle the COVID-19, particularly on how Bangladesh is dealing with this novel viral disease with its limited resources. The first case of a COVID-19 patient was detected in Bangladesh on March 8, 2020. Since then, a total of 263,503 peoples are officially reported as COVID-19 infected with 3,471 deaths until August 11, 2020. To combat the COVID-19, the government has taken various steps viz. diagnosis of the suspected cases, quarantine of doubted people and isolation of infected patients, local or regional lockdown, closure of all government and private offices, increase public awareness and enforce social distancing, etc. Moreover, to address the socio-economic situations, the government announced several financial stimulus packages of about USD 11.90 billion. However, the government got 3 months since the disease was first reported in China, but the country failed in making proper strategies including contact tracing, introducing antibody/antigen-based rapid detection kit, and also failed to make multi-disciplinary team to combat this disease. Further, limited testing facilities and inadequate treatment service along with public unawareness are the major challenges for Bangladesh to tackle this situation effectively. Along with the government, personal awareness and assistance of non-government organizations, private organizations, researchers, doctors, industrialists, and international organizations are firmly required to mitigate this highly contagious disease.

Salicylic acid antagonizes selenium phytotoxicity in rice: selenium homeostasis, oxidative stress metabolism and methylglyoxal detoxification.

We investigated the mechanistic consequences of selenium (Se)-toxicity, and its possible mitigation using salicylic acid (SA) in rice. In comparison with control, sodium selenate-exposed 'Se1' (0.5 mM) and 'Se2' (1.0 mM) plants showed accumulation of Se by 190.63 and 288.00 % in roots, 2359.42 and 2054.35 % in leaf sheaths, and 7869.91 and 9063.72 % in leaves, respectively, resulting in severe toxicity symptoms, such as growth inhibition, chlorosis, burning of leaves, and oxidative stress. In contrast, SA addition to Se-stressed plants significantly alleviated the Se-toxicity symptoms, and radically improved shoot height (28.88 %), dry biomass (34.00 %), total chlorophyll (37.51 %), soluble sugar (17.31 %) and leaf water contents (22.31 %) in 'SA + Se2' plants over 'Se2' plants. Notably, SA maintained Se-homeostasis, and decreased 'Se2'-induced oxidative stress by enhancing ascorbate level (67.75 %) and the activities of antioxidant enzymes like superoxide dismutase (20.99 %), catalase (40.97 %), glutathione peroxidase (12.26 %), and glutathione reductase (32.58 %) relative to that in 'Se2' plants. Additionally, SA protected rice plants from the deleterious effects of methylglyoxal by stimulating the activities of glyoxalase enzymes. Furthermore, SA upregulated several genes associated with reactive oxygen species (e.g. OsCuZnSOD1, OsCATB, OsGPX1 and OsAPX2) and methylglyoxal (e.g. OsGLYI-1) detoxifications. These findings unravel a decisive role of SA in alleviating Se-phytotoxicity in rice.

Methylglyoxal - a signaling molecule in plant abiotic stress responses.

Abiotic stresses are the most common harmful factors, adversely affecting all aspects of plants' life. Plants have to elicit appropriate responses against multifaceted effects of abiotic stresses by reprogramming various cellular processes. Signaling molecules play vital roles in sensing environmental stimuli to modulate gene expression, metabolism and physiological processes in plants to cope with the adverse effects. Methylglyoxal (MG), a dicarbonyl compound, is known to accumulate in cells as a byproduct of various metabolic pathways, including glycolysis. Several works in recent years have demonstrated that MG could play signaling roles via Ca2+, reactive oxygen species (ROS), K+ and abscisic acid. Recently, global gene expression profiling has shown that MG could induce signaling cascades, and an overlap between MG-responsive and stress-responsive signaling events might exist in plants. Once overaccumulated in cells, MG can provoke detrimental effects by generating ROS, forming advanced glycation end products and inactivating antioxidant systems. Plants are also equipped with MG-detoxifying glyoxalase system to save cellular organelles from MG toxicity. Since MG has regulatory functions in plant growth and development, and glyoxalase system is an integral component of abiotic stress adaptation, an in-depth understanding on MG metabolism and glyoxalase system will help decipher mechanisms underlying plant responses to abiotic stresses. Here, we provide a comprehensive update on the current knowledge of MG production and detoxification in plants, and highlight the putative functions of glyoxalase system in mediating plant defense against abiotic stresses. We particularly emphasize on the dual roles of MG and its connection with glutathione-related redox regulation, which is crucial for plant defense and adaptive responses under changing environmental conditions.

Impact of salt-induced toxicity on growth and yield-potential of local wheat cultivars: oxidative stress and ion toxicity are among the major determinants of salt-tolerant capacity.

High salinity is a major constraint for wheat productivity in many countries, including Bangladesh. Here, we examined the effects of salt-induced toxicity on growth and production of 10 local wheat cultivars by analyzing physiological, biochemical and agronomical responses to identify the salt-tolerant attributes among the contrasting genotypes. Results of cluster analyses based on salt tolerance indices of plant growth-related and yield-contributing parameters, ionic balance (Na+, K+ and Na+/K+ ratio), and stress indicators (SPAD values and proline) revealed Gourab and Shatabdi as salt-sensitive, BARI Gom 27 and 28 as salt-tolerant and the other six examined varieties as moderately salt-tolerant cultivars. Hierarchical clustering and principle component analyses also demonstrated BARI Gom 27 and 28 as the highest salt-tolerant cultivars, especially in terms of Na+/K+ ratio and proline level. Additionally, lower accumulations of hydrogen peroxide and malondialdehyde, and higher activities of antioxidant enzymes catalase, peroxidase and ascorbate peroxidase in the salt-tolerant BARI Gom 28 than in the salt-sensitive Gourab indicated reduced oxidative damage in BARI Gom 28 relative to that in Gourab. Collectively, our findings suggest that the optimum growth and yield of salt-tolerant cultivars are associated with decreased Na+/K+ ratio, increased proline level and reduced oxidative stress. Furthermore, BARI Gom 27 and 28 could be suggested as suitable cultivars for cultivation in salt-affected areas, and the contrasting salt-responsive genotypes can be used as valuable genetic resources in breeding and dissection of molecular mechanisms underlying wheat adaptation to high salinity.

Phenotypical, physiological and biochemical analyses provide insight into selenium-induced phytotoxicity in rice plants.

The present study investigated the phenotypical, physiological and biochemical changes of rice plants exposed to high selenium (Se) concentrations to gain an insight into Se-induced phytotoxicity. Results showed that exposure of rice plants to excessive Se resulted in growth retardation and biomass reduction in connection with the decreased levels of chlorophyll, carotenoids and soluble proteins. The reduced water status and an associated increase in sugar and proline levels indicated Se-induced osmotic stress in rice plants. Measurements of Se contents in roots, leaf sheaths and leaves revealed that Se was highly accumulated in leaves followed by leaf sheaths and roots. Se also potentiated its toxicity by impairing oxidative metabolism, as evidenced by enhanced accumulation of hydrogen peroxide, superoxide and lipid peroxidation product. Se toxicity also displayed a desynchronized antioxidant system by elevating the level of glutathione and the activities of superoxide dismutase, glutathione-S-transferase and glutathione peroxidase, whereas decreasing the level of ascorbic acid and the activities of catalase, glutathione reductase and dehydroascorbate reductase. Furthermore, Se triggered methylglyoxal toxicity by inhibiting the activities of glyoxalases I and II, particularly at higher concentrations of Se. Collectively, our results suggest that excessive Se caused phytotoxic effects on rice plants by inducing chlorosis, reducing sugar, protein and antioxidant contents, and exacerbating oxidative stress and methylglyoxal toxicity. Accumulation levels of Se, proline and glutathione could be considered as efficient biomarkers to indicate degrees of Se-induced phytotoxicity in rice, and perhaps in other crops.