Oxygen Species In Plants Research Articles

The Drought Tolerance Function and Tanscriptional Regulation of GhAPX7 in Gossypium hirsutum.

Drought stress significantly affects the growth, development, and yield of cotton, triggering the response of multiple genes. Among them, ascorbate peroxidase (APX) is one of the important antioxidant enzymes in the metabolism of reactive oxygen species in plants, and APX enhances the ability of plants to resist oxidation, thus increasing plant stress tolerance. Therefore, enhancing the activity of APX in cells is crucial to improving plant stress resistance. Previous studies have isolated differentially expressed proteins under drought stress (GhAPX7) in drought-resistant (KK1543) and drought-sensitive (XLZ26) plants. Thus, this study analyzed the expression patterns of GhAPX7 in different cotton tissues to verify the drought resistance function of GhAPX7 and explore its regulatory pathways. GhAPX7 had the highest expression in cotton leaves, which significantly increased under drought stress, suggesting that GhAPX7 is essential for improving antioxidant capacity and enzyme activities in cotton. GhAPX7 silencing indirectly affects pronounced leaf yellowing and wilting in drought-resistant and drought-sensitive plants under drought stress. Malondialdehyde (MDA) content was significantly increased and chlorophyll and proline content and APX enzyme activity were generally decreased in silenced plants compared to the control. This result indicates that GhAPX7 may improve drought resistance by influencing the contents of MDA, chlorophyll, proline, and APX enzyme activity through increased expression levels. Transcriptome analysis revealed that the drought-related differentially expressed genes between the control and treated groups enriched plant hormone signal transduction, MAPK signaling, and plant-pathogen interaction pathways. Therefore, the decreased expression of GhAPX7 significantly affects the expression levels of genes in these three pathways, reducing drought resistance in plants. This study provides insights into the molecular mechanisms of GhAPX7 and its role in drought resistance and lays a foundation for further research on the molecular mechanisms of response to drought stress in cotton.

The Metabolism, Detrimental Effects, and Signal Transduction Mechanism of Reactive Oxygen Species in Plants under Abiotic Stress

Plants are a major source of bio based materials, and their productivity is significantly impacted by environmental adversities with the continuous deterioration of the environment. The disruption of reactive oxygen species (ROS) production and scavenging balance is a common consequence of various abiotic stresses in plants, resulting in the excessive accumulation of ROS. However, it is crucial to acknowledging the dual role of ROS, acting both as harmful substances and signaling molecules. ROS can interact with membrane proteins, initiating a chain reaction of membrane lipid peroxidation. This process leads to a decrease in membrane lipid unsaturation and fluidity, as well as an increase in membrane permeability. Inhibited enzyme activity even lead to loss of protein function, caused DNA damage and mutations, blocked DNA replication and transcription, eventually leading to cell death. This can result in significant reductions in crop yield and biomass in bio based agricultural production. ROS also played vital role in signal molecule transduction in the process of plant resistance to stress, and worked in concert with other signal molecules to induce the stress resistance genes’ expression and enhance plant resistance. Hereto, scavenging mechanism for ROS in plants is of the essence to regulate the concentration of ROS, thus determining which role ROS play. The thermal dissipation of excess light energy effectively avoids ROS production, and the enzymatic and non-enzymatic antioxidant defense systems in plants work cooperatively to clear excessive ROS. This review provides a comprehensive summary of the production pathway, detrimental effects, scavenging mechanism and signal transduction of ROS in plants under abiotic stress.

Reducing pesticide use: Synthesis and application of ROS-SPC as an efficient nanocarrier and scavenger of reactive oxygen species in plants

There is an increasing need to reduce the use of pesticides to reduce their potential threat to food/environmental safety. At the same time, an increase in reactive oxygen species (ROS) induced by abiotic stresses in plants can lead to an increase in ROS in the plant and affect yield. In this paper, ROS-SPC was synthesised by two reactions and used as an efficient pesticide nanocarrier/adjuvant and scavenger of reactive oxygen species (ROS) in plants. By hydrophobic interaction, ROS-SPC spontaneously conjugated to fluazinam with a pesticide loading capacity (PLC) of 15.1 %. After fluazinam was conjugated to ROS-SPC, the particle size of fluazinam was reduced from 64.70 nm reduced to 19.82 nm, and the contact angle of pesticide droplets on plant leaves was significantly reduced from 59.44° to 26.76°. ROS-SPC as a carrier was tested to inhibit phytopathogenic fungi by 200 % more than conventional delivery methods. In addition, we also learned that ROS-SPC with endocytosis capability can indeed remove reactive oxygen species from plants. Tests using HUVEC cells showed that ROS-SPC has low cytotoxicity within a reasonable range of applications, and ROS-SPC was tested to have low toxicity to pollinating bees.

Perfluorobutanoic acid triggers metabolic and transcriptional reprogramming in wheat seedlings

The environmental risks of fluorinated alternatives are of great concern with the phasing out of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate. Here, multi-omics (i.e., metabolomics and transcriptomics) coupled with physiological and biochemical analyses were employed to investigate the stress responses of wheat seedings (Triticum aestivum L.) to perfluorobutanoic acid (PFBA), one of the short-chain per- and polyfluoroalkyl substances (PFAS) and PFOA alternatives, at environmentally relevant concentrations (0.1–100 ng/g). After 28 days of soil exposure, PFBA boosted the generation of OH and O2− in wheat seedlings, resulting in lipid peroxidation, protein perturbation and impaired photosynthesis. Non-enzymatic antioxidant defense systems (e.g., glutathione, phenolics, and vitamin C) and enzymatic antioxidant copper/zinc superoxide dismutase were strikingly activated (p < 0.05). PFBA-triggered oxidative stress induced metabolic and transcriptional reprogramming, including carbon and nitrogen metabolisms, lipid metabolisms, immune responses, signal transduction processes, and antioxidant defense-related pathways. Down-regulation of genes related to plant-pathogen interaction suggested suppression of the immune-response, offering a novel understanding on the production of reactive oxygen species in plants under the exposure to PFAS. The identified MAPK signaling pathway illuminated a novel signal transduction mechanism in plant cells in response to PFAS. These findings provide comprehensive understandings on the phytotoxicity of PFBA to wheat seedlings and new insights into the impacts of PFAS on plants.

Exogenous treatment with N-acetylglutamic acid confers tolerance to heat stress in plants.

Heat stress, which occurs when temperatures exceed the optimal range for growth, challenges the maintenance of crop yield because it disrupts plant homeostasis at the cellular and developmental levels. Chemical priming, which can activate the response to environmental stress using chemical compounds, is a promising method of maintaining plant growth under stressful conditions. Recently, we found that the non-proteogenic amino acid N-acetylglutamic acid (NAG) confers tolerance to oxidative stress through the activation of genes related to scavenging reactive oxygen species in plants. However, it has been unknown whether NAG alleviates environmental stress except oxidative stress. Here, we revealed that the response to heat stress was enhanced by exogenous treatment with NAG in plants. NAG alleviated the reduction in chlorophyll content induced by heat stress in Arabidopsis thaliana. Gene expression analysis showed that NAG activates the transcription factor HSFA2, which is regarded as a master regulator of the transcriptional cascade in response to heat stress. NAG induces histone H4 acetylation, an active histone modification, at the HSFA2 locus, suggesting that NAG could activate the expression of HSFA2 based on epigenetic modifications such as histone acetylation. Additionally, we found that Oryza sativa treated with NAG showed tolerance to heat stress. These results suggest that NAG could be used for chemical priming in the maintenance of plant growth under heat-stress conditions.

Types of Membrane Transporters and the Mechanisms of Interaction between Them and Reactive Oxygen Species in Plants.

Membrane transporters are proteins that mediate the entry and exit of substances through the plasma membrane and organellar membranes and are capable of recognizing and binding to specific substances, thereby facilitating substance transport. Membrane transporters are divided into different types, e.g., ion transporters, sugar transporters, amino acid transporters, and aquaporins, based on the substances they transport. These membrane transporters inhibit reactive oxygen species (ROS) generation through ion regulation, sugar and amino acid transport, hormone induction, and other mechanisms. They can also promote enzymatic and nonenzymatic reactions in plants, activate antioxidant enzyme activity, and promote ROS scavenging. Moreover, membrane transporters can transport plant growth regulators, solute proteins, redox potential regulators, and other substances involved in ROS metabolism through corresponding metabolic pathways, ultimately achieving ROS homeostasis in plants. In turn, ROS, as signaling molecules, can affect the activity of membrane transporters under abiotic stress through collaboration with ions and involvement in hormone metabolic pathways. The research described in this review provides a theoretical basis for improving plant stress resistance, promoting plant growth and development, and breeding high-quality plant varieties.

The Influence of Salt Stress on the Content of Vitamin C in the Leaves of some Varieties and Lines of Bitter Cucumber (Momordica charantia)

Bitter cucumber is a tropical and subtropical plant with a long history of medicinal use. Soil salinity is a major abiotic stress that affects the morphology and physiology of plants leading to reduced growth, production yield or in some cases their death. Salt stress increases the accumulation of reactive oxygen species in plants. They developed adaptation mechanisms by increasing the level of antioxidants, including vitamin C. The aim was to estimate the amount of vitamin C in the studied plants to determine the ability to adapt to salinity and improve nutritional properties. To carry out the experiment, two varieties and three experimental lines of bitter cucumber subjected to saline stress through treatments with saline solutions of different concentrations were used. The estimation of vitamin C content was carried out by UV-Vis spectrophotometry using the calibration curve method with standard L-ascorbic acid and KMnO4. After performing the analysis of variance on the varieties and lines of bitter cucumber, subjected to salt stress by applying the two treatments, it was found that the accumulation of vitamin C was insignificantly influenced by the factor a-the number of the treatment, but it was significantly influenced by the factor b-the concentration saline solution.

Genome-wide identification of Glutathione peroxidase (GPX) family genes and silencing TaGPX3.2A reduced disease resistance in wheat

Glutathione peroxidase (GPX) is a crucial enzyme that scavenges reactive oxygen species in plants, playing a vital role in enhancing plant stress resistance. In this study, we identified 14 glutathione peroxidase genes (TaGPXs) from common hexaploid wheat (Triticum aestivum L.). These genes were subsequently categorized into three distinct groups based on their phylogenetic relationships. Simultaneously, a preliminarily analysis was conducted on the protein characteristics, chromosome localization, gene structure, cis-regulatory elements and transcriptome. Using reverse transcription quantitative PCR to analyze the expression patterns of five GPX genes that were investigated under various exogenous hormone treatments. According to the qRT-PCR analysis, it indicated that TaGPX genes have the distinct expression patterns. The enzyme activities in transiently overexpressed Nicotiana benthamiana (TaGPX3.2A and TaGPX3.4A) leaves were measured under salt and drought stresses, showed that peroxidase (POD) exhibited higher enzyme activity under stresses. Silencing TaGPX3.2A by virus-induced gene silencing (VIGS) led to reduced resistance of wheat to Fusarium graminearum, indicating that TaGPX3.2A plays a crucial role in enhancing wheat resistance against F. graminearum. This research provides a foundational basis for further investigations on the functional characterization of TaGPXs family members. And in the future it is provides valuable resources for genetic improvement of wheat resistance.

Chitosan Reduces Damages of Strawberry Seedlings under High-Temperature and High-Light Stress

High-temperature and high-light are the main adversity stresses faced by strawberry seedlings and open-field cultivation in summer. Chitosan (CTS) is widely used in agriculture as a soil amendment, plant growth regulator, and promoter of cold resistance. However, the effects of CTS on strawberry seedlings under the combined stress of high-temperature and high-light are unclear. This study aimed to determine the effect of CTS on strawberry seedlings under the combined stress of high-temperature and high-light. In this study, Xuelixiang strawberry was used as the experimental plant material. The leaves were sprayed with 100 mg/Kg CTS or deionized aqueous solution and placed under high-temperature and high-light (38 °C, 1800 μ mol·m−2·s−1, respectively) for 8 h. In addition, a suitable temperature and light (23 °C, 400 μ mol·m−2·s−1, respectively) was sprayed with deionized water as a control. The results showed that compared with non-CTS treatment, the chlorophyll (Chl) content in strawberry plants increased by 16.9% after CTS treatment; the net CO2 exchange (Pn) increased by 74.9%; and the maximum photochemical efficiency increased by 20.1%. In addition, CTS treatment increased the content of antioxidants; increased osmotic adjustment substances; improved the activity of reduced glutathione with reduced ascorbic acid (AsA-GSH) circulating antioxidant enzymes; removed reactive oxygen species in plants in time; and reduced the damage of reactive oxygen species to photosynthetic organs and cell membranes, thereby reducing high-temperature and high-light injury to strawberry seedlings. This study shows that CTS can improve the negative effects of high-temperature and high-light stress on strawberry seedlings.

Reactive oxygen species in plants: an invincible fulcrum for biotic stress mitigation.

Climate change-associated environmental vagaries have amplified the incidence of pests and pathogens on plants, thus imparting the increased quest for management strategies. Plants respond to stresses through intricate signaling networks that regulate diverse cellular mechanisms. Reactive oxygen species (ROS) are cardinal towards the maintenance of normal plant activities as well as improving stress management. Plants that exhibit a fine balance between ROS levels and its management apparently mitigate stresses better. There have been very many compendiums on signaling and management of ROS during several abiotic stresses. However, expansion of knowledge related to ROS induction and homeostasis during biotic stresses is pertinent. Hence, considering its importance, we provide insights in this review on how plants signal and manage ROS upon an oxidative burst during their interaction with pathogens and herbivores. Substantial degree of molecular changes and pivotal roles of ROS have been detected during phyto-pathogen/herbivore interactions, opening novel platforms to understand signaling/management of events under varied biotic stresses. It is interesting to know that, though plants react to biotic stresses through oxidative burst, receptors and elicitors involved in the signal transduction differ across stresses. The review provides explicit details about the specific signaling of ROS production in plants under pathogen and herbivore attack. Furthermore, we also provide an update about tackling the accumulated ROS under biotic stresses as another pivotal step. ROS signaling and homeostasis can be exploited as critical players and a fulcrum to tackle biotic stresses, thus paving the way for futuristic combinatorial stress management strategies. KEY POINTS: •The review is a comprehension of redox signaling and management in plants during herbivory and pathogen infection •Reactive oxygen species (ROS) is an important factor during normal plant activities as well as in their response to stresses. Diverse modes of ROS signaling and management have been observed during both biotic stresses independently •Exploration of plant biology in multi-stress resistant plants like the crop wild relatives could pave the way for combinatorial management of stress for a better tomorrow.

Plant Antioxidants Affect Human and Gut Health, and Their Biosynthesis Is Influenced by Environment and Reactive Oxygen Species

Many environmental stresses cause an increase in reactive oxygen species in plants and alter their nutritional value. Plants respond to many stresses by producing increased amounts of compounds with antioxidant properties including vitamins, phenylpropanoids and carotenoids. Such compounds have wide-ranging health-promoting effects in humans that are partly due to their antioxidant function because oxidative stress underlies many human diseases. Some of these compounds have complex interactions with the gut, promoting gut health and changing the gut microbiome, whereas the gut influences the bioavailability of the ingested compounds and may metabolize them into products with different effects on health than the original compound. Substantial efforts have been made to increase the nutritional value of crops through breeding or transgenic approaches, but comparatively little effort has been directed towards increasing nutritional value through crop management and environment, which may present another approach to enhance the nutritional quality.

Coupled effects of microplastics and heavy metals on plants: Uptake, bioaccumulation, and environmental health perspectives.

Microplastic pollution has severe ecological and environmental concerns because of its enormous production and discharge in natural ecosystems worldwide. Microplastics interact with heavy metals and metalloids like arsenic, chromium, copper, cadmium, and lead in soil and can cause detrimental effects on soil structure and microbial activities and subsequently impact the plants and human health. This article focuses on microplastic translocation from soil to plants together with heavy metals. Microplastic exposure impacts biomass, photosynthetic activity, chlorophyll content, root and shoot length in the plants through apoplastic and symplastic pathways. Microplastics can also indirectly affect the plant growth by changing soil nutrient content and microbial community structure. At the same time, microplastics can absorb heavy metals and increase phytotoxicity in plants. However, the current knowledge about the coupled effect of heavy metals and microplastics bioaccumulation in plants is limited. It is postulated that heavy metals and microplastics collectively impact the chlorophyll content, photosynthetic activity, and induction of reactive oxygen species in plants. This work also outlines the environmental health perspectives based on microplastic and heavy metals toxicity and provides a guideline for future research on the coupled effects of heavy metals and microplastics on plants and humans.

Endoplasmic Reticulum Stress and Reactive Oxygen Species in Plants.

The endoplasmic reticulum (ER) is a key compartment responsible for protein processing and folding, and it also participates in many signal transduction and metabolic processes. Reactive oxygen species (ROS) are important signaling messengers involved in the redox equilibrium and stress response. A number of abiotic and biotic stresses can trigger the accumulation of unfolded or misfolded proteins and lead to ER stress. In recent years, a number of studies have reported that redox metabolism and ROS are closely related to ER stress. ER stress can benefit ROS generation and even cause oxidative burden in plants, finally leading to oxidative stress depending on the degree of ER stress. Moreover, ER stress activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated ROS signaling, increases antioxidant defense mechanisms, and alters the glutathione (GSH) redox state. Meanwhile, the accumulation of ROS plays a special role in inducing the ER stress response. Given these factors, plants have evolved a series of complex regulatory mechanisms to interact with ROS in response to ER stress. In this review, we summarize the perceptions and responses of plant ER stress and oxidative protein folding in the ER. In addition, we analyze the production and signaling of ROS under ER stress in detail in order to provide a theoretical basis for reducing ER stress to improve the crop survival rate in agricultural applications.

Reactive Oxygen Species in Plants: From Source to Sink.

Reactive oxygen species (ROS, partial reduction or derivatives of free radicals) are highly reactive, dangerous and can cause oxidative cell death. In addition to their role as toxic by-products of aerobic metabolism, ROS play a role in the control and regulation of biological processes such as growth, the cell cycle, programmed cell death, hormone signaling, biotic and abiotic stress reactions and development. ROS always arise in plants as a by-product of several metabolic processes that are located in different cell compartments, or as a result of the inevitable escape of electrons to oxygen from the electron transport activities of chloroplasts, mitochondria and plasma membranes. These reactive species are formed in chloroplasts, mitochondria, plasma membranes, peroxisomes, apoplasts, the endoplasmic reticulum and cell walls. The action of many non-enzymatic and enzymatic antioxidants present in tissues is required for efficient scavenging of ROS generated during various environmental stressors. The current review provides an in-depth look at the fate of ROS in plants, a beneficial role in managing stress and other irregularities. The production sites are also explained with their negative effects. In addition, the biochemical properties and sources of ROS generation, capture systems, the influence of ROS on cell biochemistry and the crosstalk of ROS with other signaling molecules/pathways are discussed.

Initiation and Execution of Programmed Cell Death and Regulation of Reactive Oxygen Species in Plants.

Programmed cell death (PCD) plays crucial roles in plant development and defence response. Reactive oxygen species (ROS) are produced during normal plant growth, and high ROS concentrations can change the antioxidant status of cells, leading to spontaneous cell death. In addition, ROS function as signalling molecules to improve plant stress tolerance, and they induce PCD under different conditions. This review describes the mechanisms underlying plant PCD, the key functions of mitochondria and chloroplasts in PCD, and the relationship between mitochondria and chloroplasts during PCD. Additionally, the review discusses the factors that regulate PCD. Most importantly, in this review, we summarise the sites of production of ROS and discuss the roles of ROS that not only trigger multiple signalling pathways leading to PCD but also participate in the execution of PCD, highlighting the importance of ROS in PCD.

Microplastic residues in wetland ecosystems: Do they truly threaten the plant-microbe-soil system?

The ecological stress of microplastic contamination to ecosystem functioning and biota raises concerns worldwide, but the impacts of microplastics on wetland ecosystems (e.g., plants, microbes, and soil) have not been fully elucidated. In this study, we used a controlled pot experiment to determine the effects of different types (PS, PVC, PP and PE) of microplastics on the growth performance of wetland plants, soil chemical properties, enzyme systems and microbial communities. Microplastics can change the germination strategies of seeds, and there was also a reduction in fresh weight and plant height in Bacopa sp. Chlorophyllb synthesiswas significantly reduced in mixed microplastic treatments compared with controls. Microplastic addition in soil caused higher concentrations of reactive oxygen species in plants, which led to increased lipid peroxidation and activation of the antioxidant defence system. The organic matter, potassium, total nitrogen and phosphorus changed significantly in the presence of the four forms of microplastics, while soil pH was not substantially affected. Microplastics had a negative effect on soil enzyme activity, for example, PS MP particles significantly decreased sucrase activities in the soil after 40days. The results of this study showed that microplastic addition decreased the richness and diversity of bacterial. When soil was exposed to polystyrene microplastics, the richness and diversity of algae significantly increased on the soil surface. Thus, microplastics can alters the structure of soil microbial communities, resulting in the enrichment of some special soil microbial taxa involved in nitrogen cycling. These results indicate both the direct and indirect effects of plastic residues on the plant-microbe-soil system, which has implications for potential further impacts on wetland ecosystem functioning.

Transcriptomic and physiological analysis revealed the ammonium tolerance mechanisms of Myriophyllum aquaticum

The macrophyte Myriophyllum aquaticum was found to have strong resistance to the high ammonium (NH4+) in the aquatic environment and high effectiveness to treat swine wastewater. In order to understand the NH4+ tolerance and toxicity mechanisms, we conducted on the investigations of transcriptomic and physiological response of M. aquaticum to NH4+ stress. The plant was grown in Hoagland’s solutions with high (10 mM; N2) and extra-high (70 mM; N3) NH4+ concentrations, using 0.2 mM NH4+ as the control (N1) in a greenhouse, and then proceeded with Illumina next-generation sequencing and PacBio single-molecule real-time sequencing. The N3 plants appeared obvious NH4+ toxicity symptoms, while the N1 and N2 plants showed vigorous growth after two-weeks treatment. A total of 31,678 and 35,072 differentially expressed genes were identified in M. aquaticum under the N2 and N3 treatments, respectively. Transcriptional up-regulation of the light-harvesting chlorophyll a/b binding proteins genes in the leaves contributed to high NH4+ resistance in M. aquaticum. Transcriptional regulation of catalase genes likely balanced the reactive oxygen species in plants under high NH4+ conditions. Transcriptional down- or/and up- regulation of nitrogen metabolism genes, including NH4+ transporter, glutamine synthetase, glutamate synthetase, glutamate dehydrogenase, and asparagine synthetase genes were indispensable for NH4+ homeostasis through the NH4+ uptake, transport, and assimilation under high NH4+ concentrations. Our study provides insights into the molecular and physiological mechanisms of M. aquaticum response to NH4+ stress, and our multi-transcriptome database is beneficial to future investigations on this species. These results lay a theoretical foundation for the treatment of high-strength NH4+ in swine wastewater by M. aquaticum.

Bitkilerde Aktif Oksijen Türleri ve Oksidatif Stres

Aerobik organizmalar için oksijen vazgeçilmez bir moleküldür. Biyotik ve abiyotik stres faktörleri altında bitkilerde elektron taşınımı ile ilgili reaksiyonlar aktif oksijen türlerinin oluşum hızını artırır. Bu reaksiyonlarda elektronlar stres faktörlerinin etkisiyle asıl hedef molekül yerine oksijene verilir. Bu şekilde başlayan zincirleme reaksiyonlar bitki dokularında süperoksit radikali, hidrojen peroksit ve hidroksil radikali gibi aktif oksijen türlerinin birikim göstermeye başlamasına yol açar. Antioksidant sistemin yeterince aktive edilememesi durumunda oldukça reaktif olan aktif oksijen türleri hücresel bileşenlere zarar vermeye başlar. Bu olay oksidatif stres olarak bilinir. Aktif oksijen türleri bitki hücrelerindeki birçok organelde oluşabilir. Kloroplastlar bitki hücrelerinde aktif oksijen türlerini oluşturma kapasitesi bakımından en aktif organellerdir. Bunun dışında mitokondriler, peroksizomlar, endoplazmik retikulum gibi organellerle apoplastik bölgede de aktif oksijen oluşumu gözlenir. Stres koşulları altında sekonder bir stres olarak ortaya çıkan oksidatif stres tarımsal verimliliği tehdit eden en önemli faktör olarak kabul edilmektedir. Bu derlemede bitki hücrelerinde aktif oksijen türlerinin oluşumuna neden olan metabolik olaylar, bu bileşiklerin kimyasal özellikleri ve oksidatif hasar oluşturma mekanizmaları tartışılmıştır.

Genome-wide association studies using 50K rice genic SNP chip unveil genetic architecture for anaerobic germination of deep-water rice population of Assam, India.

North Eastern part of India such as Assam is inundated by flood every year where the farmers are forced to grow the traditional tall deep-water rice. Genetic improvement of this type of rice is slow because of insufficient knowledge about their genetic architecture and population structure. In the present investigation, the genetic diversity architecture of 94 deep-water rice genotypes of Assam and association mapping strategy was, for the first time, applied to determine the significant SNPs and genes for deep-water rice. These genotypes are known for their unique elongation ability under deep-water condition. The anaerobic germination (AG) related trait-associated genes identified here can provide affluent resources for rice breeding especially in flood-prone areas. We investigated the genome-wide association studies (GWAS) using 50K rice genic SNP chip across 94 deep-water rice genotypes collected from different flood-prone districts/villages of Assam. Population structure and diversity analysis revealed that these genotypes were stratified into four sub-populations. Using GWAS approach, 20 significant genes were identified and found to be associated with AG-related traits. Of them, two most relevant genes (OsXDH1and SSXT) have been identified which explain phenotypic variability (R2 > 20%) in the population. These genes were located in Chr 3 (LOC_Os03g31550) which encodes for enzyme xanthine dehydrogenase 1(OsXDH1) and in Chr 12 (LOC_Os12g31350) which encodes for SSXT family protein. Both of these genes were found to be associated with anaerobic response index (increase in the coleoptile length under water in anaerobic condition with respect to control), respectively. Interestingly, OsXDH1is involved in purine catabolism pathway and acts as a scavenger of reactive oxygen species in plants, whereas SSXT is GRF1-interacting factor 3. These two candidate genes associated with AG of deep-water rice have been found to be reported for the first time. Thus, this study provides a greater resource for breeders not only for improvement of deep-water rice, but also for AG tolerant variety useful for direct-seeded rice in flood-affected areas.

Nitrated Nucleotides: New Players in Signaling Pathways of Reactive Nitrogen and Oxygen Species in Plants.

Nitration of diverse biomolecules, including proteins, lipids and nucleic acid, by reactive nitrogen species represents one of the key mechanisms mediating nitric oxide (NO) biological activity across all types of organisms. 8-nitroguanosine 3′5′-cyclic monophosphate (8-nitro-cGMP) has been described as a unique electrophilic intermediate involved in intracellular redox signaling. In animal cells, 8-nitro-cGMP is formed from guanosine-5′-triphosphate by a combined action of reactive nitrogen (RNS) and oxygen species (ROS) and guanylate cyclase. As demonstrated originally in animal models, 8-nitro-cGMP shows certain biological activities closely resembling its analog cGMP; however, its regulatory functions are mediated mainly by its electrophilic properties and chemical interactions with protein thiols resulting in a novel protein post-translational modification termed S-guanylation. In Arabidopsis thaliana, 8-nitro-cGMP was reported to mediate NO-dependent signaling pathways controlling abscisic acid (ABA)-induced stomatal closure, however, its derivative 8-mercapto-cGMP (8-SH-cGMP) was later shown as the active component of hydrogen sulfide (H2S)-mediated guard cell signaling. Here we present a survey of current knowledge on biosynthesis, metabolism and biological activities of nitrated nucleotides with special attention to described and proposed functions of 8-nitro-cGMP and its metabolites in plant physiology and stress responses.