Understanding the Impacts of Crude Oil and its Induced Abiotic Stresses on Agrifood Production: A Review

Nanoremediation strategies to address environmental problems

A rapid rise in population, extensive anthropogenic activities including agricultural practices, up-scaled industrialization, massive deforestation, etc. are the leading causes of environmental degradation. Such uncontrolled and unabated practices have affected the quality of environment (water, soil, and air) synergistically by accumulating huge quantities of organic and inorganic pollutants in it. Environmental contamination is posing a threat to the existing life on the Earth, therefore, demands the development of sustainable environmental remediation approaches. The conventional physiochemical remediation approaches are laborious, expensive, and time-consuming. In this regard, nanoremediation has emerged as an innovative, rapid, economical, sustainable, and reliable approach to remediate various environmental pollutants and minimize or attenuate the risks associated with them. Owing to their unique properties such as high surface area to volume ratio, enhanced reactivity, tunable physical parameters, versatility, etc. nanoscale objects have gained attention in environmental clean-up practices. The current review highlights the role of nanoscale objects in the remediation of environmental contaminants to minimize their impact on human, plant, and animal health; and air, water, and soil quality. The aim of the review is to provide information about the applications of nanoscale objects in dye degradation, wastewater management, heavy metal and crude oil remediation, and mitigation of gaseous pollutants including greenhouse gases.

Correlation of soil microbiome with crude oil contamination drives detection of hydrocarbon degrading genes which are independent to quantity and type of contaminants

The impacts of crude oil contamination on soil microbial populations were explored in seven different polluted areas near oil and gas drilling sites and refineries of Assam, India. Using high-throughput sequencing techniques, the functional genes and metabolic pathways involved in the bioconversion of crude oil contaminants by the indigenous microbial community were explored. Total petroleum hydrocarbon (TPH) concentrations in soil samples ranged from 1109.47 to 75,725.33 mg/kg, while total polyaromatic hydrocarbon (PAH) concentrations ranged from 0.780 to 560.05 mg/kg. Pyrene, benzo[a]anthracene, naphthalene, phenanthrene, and anthracene had greater quantities than the maximum permitted limits, suggesting a greater ecological risk, in comparison to other polyaromatic hydrocarbons. According to the metagenomic data analysis, the bacterial phyla Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroides were the most prevalent among all polluted areas. The most prominent hydrocarbon degraders in the contaminated sites included Burkholderia, Mycobacterium, Polaromonas, and Pseudomonas. However, the kinds of pollutants and their concentrations did not correlate with the abundances of respective degrading genes for all polluted locations, as some of the sites with little to low PAH contamination had significant abundances of corresponding functional genes for degradation. Thus, the findings of this study imply that the microbiome of hydrocarbon-contaminated areas, which are biologically involved in the degradation process, has various genes, operons and catabolic pathways that are independent of the presence of a specific kind of contaminant.

Eco-physiological response and genotoxicity induced by crude petroleum oil in the potential phytoremediator Vinca rosea L

Background

Phytoremediation is determined as an emerging green technology suitable for the safe remediation and restoration of polluted terrestrial and aquatic environments. In this study, the assessment of an ornamental plant, Vinca rosea L., as a phytoremediator of crude oil in polluted soils was conducted. In an open greenhouse experiment, plants were raised in sandy-clayey soils treated with 1, 3, 5, and 7% oil by weight. The experiment was conducted over 5 months.

Results

Total petroleum hydrocarbon (TPH) degradation percentage by V. rosea after a 5-month growth period ranged from 86.83 ± 0.44% to 59.05% ± 0.45% in soil treated with 1 and 7%, respectively. Plants raised in polluted soils demonstrated a dramatic reduction in germination rates, in addition to growth inhibition outcomes shown from decreased plant height. An increase in branching was observed with an increase in oil pollution percentages. Moreover, the phytomass allocated to the leaves was higher, while the phytomass witnessed lower values for fine roots, flowering and fruiting when compared to the controls. Apart from the apparent morphological changes, there was a decrease in chlorophyll a/b ratio, which was inversely proportional to the oil pollution level. The contents of carotenoids, tannins, phenolics, flavonoids, and antioxidant capacity were elevated directly with an increase in oil pollution level. The start codon-targeted (SCoT) polymorphisms and inter-simple sequence repeat (ISSR) primers showed the molecular variations between the control and plants raised in polluted soils. The genetic similarity and genomic DNA stability were negatively affected by increased levels of crude oil pollution.

Conclusions

The ability of V. rosea to degrade TPH and balance the increased or decreased plant functional traits at the macro and micro levels of plant structure in response to crude oil pollution supports the use of the species for phytoremediation of crude oil-polluted sites. The genotoxic effects of crude oil on V. rosea still require further investigation. Further studies are required to demonstrate the mechanism of phenolic, flavonoid, and antioxidant compounds in the protection of plants against crude oil pollution stress. Testing different molecular markers and studying the differentially expressed genes will help understand the behavior of genetic polymorphism and stress-resistant genes in response to crude oil pollution.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00412-6.

Ecological risk assessment of priority PAHs pollutants in crude oil contaminated soil and its impacts on soil biological properties

Polycyclic aromatic hydrocarbons (PAHs) are one of the major toxic constituents of crude oil and therefore, an understanding on PAHs associated risks and their relationship with soil biological parameters are necessary for adopting effective risk-based and site specific remediation strategies in the contaminated soil. Here, risks evaluation of eight detected PAHs in terms of toxic equivalent concentration (TEQ_C), benzo(a)pyrene equivalent (BaPeq), contamination factor (CF), pollution load index (PLI), hazard quotient (HQ), hazard index (HI), toxic unit for individual PAHs (TU) and PAHs mixture (TU_m) have been evaluated. Besides, the effect of PAHs contamination on soil biological properties has also been investigated and correlated with PAHs concentrations. The TEQc of eight PAHs was recorded in the range of 0.06-5.0 mg kg^-1 soil_, whereas the BaPeq value was 25.3 mg kg^-1 soil which exceed the permissible limit. Similarly, CF (85.5-1668.2), PLI (322.8), HQ (311.7-8340.9), HI (26,443.8), TU (227.9-3821.6) and TU_m(7916.2) also exceed the permissible values for non-toxic conditions indicating carcinogenic risk for humans. Besides, activities of soil dehydrogenase, urease, alkaline-phosphatase, catalase, amylase and cellulase were decreased by 1.5-2.3 folds in the contaminated soil than control. The results of Pearson's correlation matrix also established negative impact of PAHs on the soil's biological properties.

Understanding biochemical defense and phytoremediation potential of Leucas aspera in crude oil polluted soil

The phytoremediation potential and enzymatic defense of a medicinal herb Leucas aspera was studied in the crude oil contaminated soil. The productivity, antioxidants, and phytochemical and functional group profiles of the plant species in stress conditions were investigated. Besides, changes in enzymes, beneficial bacterial population, and physico-chemical and total oil and grease (TOG) profiles in the contaminated soil were also studied. The results showed improvement in physico-chemical conditions, increase in beneficial bacterial population (4.1-5.4 folds), and decrease in TOG (31.3%) level of the contaminated soil by end of the experimental trials. The L. aspera treated contaminated soil showed enhancement in dehydrogenase (32.3%), urease (102.8%), alkaline phosphatase (174.4%), catalase (68.5%), amylase (76.16%), and cellulase (23.6%) activities by end of the experimental trials. Furthermore, there were significant variations in leaf area index, chlorophyll, and biomass contents of the experimental plant as against the initial level and control. Besides, the significant reduction in IC₅₀ values (24-27.4%) of L. aspera samples grown in contaminated soil confirms the strong antioxidant enzymatic defense of the plant species against the crude oil associated abiotic stress. The Fourier-transform infrared (FT-IR) analysis confirmed the uptake and metabolism of aliphatic hydrocarbons, aldehydes, alkyl halides, and nitro compounds by the experimental plant from the contaminated soil.

Pseudomonas in environmental bioremediation of hydrocarbons and phenolic compounds- key catabolic degradation enzymes and new analytical platforms for comprehensive investigation

Pollution of the environment with petroleum hydrocarbons and phenolic compounds is one of the biggest problems in the age of industrialization and high technology. Species of the genus Pseudomonas, present in almost all hydrocarbon-contaminated areas, play a particular role in biodegradation of these xenobiotics, as the genus has the potential to decompose various hydrocarbons and phenolic compounds, using them as its only source of carbon. Plasticity of carbon metabolism is one of the adaptive strategies used by Pseudomonas to survive exposure to toxic organic compounds, so a good knowledge of its mechanisms of degradation enables the development of new strategies for the treatment of pollutants in the environment. The capacity of microorganisms to metabolize aromatic compounds has contributed to the evolutionally conserved oxygenases. Regardless of the differences in structure and complexity between mono- and polycyclic aromatic hydrocarbons, all these compounds are thermodynamically stable and chemically inert, so for their decomposition, ring activation by oxygenases is crucial. Genus Pseudomonas uses several upper and lower metabolic pathways to transform and degrade hydrocarbons, phenolic compounds, and petroleum hydrocarbons. Data obtained from newly developed omics analytical platforms have enormous potential not only to facilitate our understanding of processes at the molecular level but also enable us to instigate and monitor complex biodegradations by Pseudomonas. Biotechnological application of aromatic metabolic pathways in Pseudomonas to bioremediation of environments polluted with crude oil, biovalorization of lignin for production of bioplastics, biofuel, and bio-based chemicals, as well as Pseudomonas-assisted phytoremediation are also considered.

Effects of oil contamination on plant growth and development: a review

Oil spills generate several environmental impacts and have become more common with the increase in petroleum extraction, refining, transportation, and trade. In soil, oil contamination increases water and nutrient availability and compaction, directly affecting plant growth and development. Different aspects of phytotoxicity can be observed and will vary according to the characteristics of soil and plants. Oil-contaminated soil also results in negative effects on biomass and changes in leaves and roots. Investigating the effects of oil contamination on plant growth and development can aid in the conservation of plant species and in the development of techniques such as bioremediation and biomonitoring. Thus, this review aims to discuss the main effects of oil contamination on plants, such as environmental stress and morphological, physiological, and anatomical changes, and the strategies developed by plants to survive contamination, as well as to identify plants with phytoremediation potential that can assist in removing oil from the environment.

Physiological and biochemical characteristic of Miscanthus × giganteus grown in heavy metal - oil sludge co-contaminated soil

The effect of oil sludge and zinc, present in soil both separately and as a mixture on the physiological and biochemical parameters of Miscanthus × giganteus plant was examined in a pot experiment. The opposite effect of pollutants on the accumulation of plant biomass was established: in comparison with uncontaminated control the oil sludge increased, and Zn reduced the root and shoot biomass. Oil sludge had an inhibitory effect on the plant photosynthetic apparatus, which intensified in the presence of Zn. The specific antioxidant response of M. × giganteus to the presence of both pollutants was a marked increase in the activity of superoxide dismutase (mostly owing to oil sludge) and glutathione-S-transferase (mostly owing to zinc) in the shoots. The participation of glutathione-S-transferase in the detoxification of both the organic and the inorganic pollutants was assumed. Zn inhibited the activity of laccase-like oxidase, whereas oil sludge promoted laccase and ascorbate oxidase activities. This finding suggests that these enzymes play a part in the oxidative detoxification of the organic pollutаnt. With both pollutants used jointly, Zn accumulation in the roots increased 6-fold, leading to increase in the efficiency of soil clean-up from the metal. In turn, Zn did not significantly affect the soil clean-up from oil sludge. This study shows for the first time the effect of co-contamination of soil with oil sludge and Zn on the physiological and biochemical characteristics of the bioenergetic plant M. × giganteus. The data obtained are important for understanding the mechanisms of phytoremediation with this plant.

Alterations of endophytic microbial community function in Spartina alterniflora as a result of crude oil exposure

The 2010 Deepwater Horizon disaster remains one of the largest oil spills in history. This event caused significant damage to coastal ecosystems, the full extent of which has yet to be fully determined. Crude oil contains toxic heavy metals and substances such as polycyclic aromatic hydrocarbons that are detrimental to some microbial species and may be used as food and energy resources by others. As a result, oil spills have the potential to cause significant shifts in microbial communities. This study assessed the impact of oil contamination on the function of endophytic microbial communities associated with saltmarsh cordgrass (Spartina alterniflora). Soil samples were collected from two locations in coastal Louisiana, USA: one severely affected by the Deepwater Horizon oil spill and one relatively unaffected location. Spartina alterniflora seedlings were grown in both soil samples in greenhouses, and GeoChip 5.0 was used to evaluate the endophytic microbial metatranscriptome shifts in response to host plant oil exposure. Oil exposure was associated with significant shifts in microbial gene expression in functional categories related to carbon cycling, virulence, metal homeostasis, organic remediation, and phosphorus utilization. Notably, significant increases in expression were observed in genes related to metal detoxification with the exception of chromium, and both significant increases and decreases in expression were observed in functional gene subcategories related to hydrocarbon metabolism. These findings show that host oil exposure elicits multiple changes in gene expression from their endophytic microbial communities, producing effects that may potentially impact host plant fitness.

Effects of Coal and Sewage Sludge Ashes on Macronutrient Content in Maize (Zea mays L.) Grown on Soil Contaminated with Eco-Diesel Oil

Petroleum hydrocarbons, as aggressive components of diesel oils, after migration to the land environment can alter the activity and efficiency of ecosystems. They can also be dangerous to animal and human health. Eco-friendly methods for the reclamation of affected soils is necessary to manage degraded lands. One such method is the use of ashes. The aim of this research was to determine how soil pollution with diesel oil (brand name, Eco-Diesel) affects the chemical composition of maize (Zea mays L.) and whether the application of ash from a combined heat and power plant, as well as from sewage sludge incineration, could reduce the potentially adverse impact of diesel oil on plants. The research results demonstrated that soil contamination with Eco-Diesel oil modified the content of selected macronutrients in the analyzed crop plant. Eco-Diesel oil had a negative effect on maize yield. The highest diesel oil dose in a series without neutralizing substances had a positive effect on the accumulation of most elements, except nitrogen and sodium. Soil enrichment with ash differentiated the content of macronutrients, mainly nitrogen and phosphorus, in the aerial biomass of maize. The ashes increased the yield of maize and content of some macronutrients, mainly nitrogen but also calcium, the latter in a series where soil was treated with ash from sewage sludge thermal recycling. Both types of ash also resulted in a decrease in the plant content of phosphorus, while ash from hard coal caused a slight reduction in the content of potassium in maize. Ash of different origins can be an effective solution in the reclamation of degraded soils, which may then be used for growing energy crops.

Bioprospecting of indigenous biosurfactant-producing oleophilic bacteria for green remediation: an eco-sustainable approach for the management of petroleum contaminated soil

In the present study, the efficiency of four different strains of Pseudomonas aeruginosa and their biosurfactants in the bioremediation process were investigated. The strains were found to be capable of metabolizing a wide range of hydrocarbons (HCs) with preference for high molecular weight aliphatic (ALP) over aromatic (ARO) compounds. After treating with individual bacteria and 11 different consortia, the residual crude oils were quantified and qualitatively analyzed. The bacterial strains degraded ALP, ARO, and nitrogen, sulphur, oxygen (NSO) containing fractions of the crude oil by 73-67.5, 31.8-12.3 and 14.7-7.3%, respectively. Additionally, the viscosity of the residual crude oil reduced from 48.7 to 34.6-39 mPa s. Further, consortium designated as 7 and 11 improved the degradation of ALP, ARO, and NSO HCs portions by 80.4-78.6, 42.7-42.4 and 21.6-19.2%, respectively. Moreover, addition of biosurfactant further increased the degradation performance of consortia by 81.6-80.7, 43.8-42.6 and 22.5-20.7%, respectively. Gas chromatographic analysis confirmed the ability of the individual strains and their consortium to degrade various fractions of crude oil. Experiments with biosurfactants revealed that polyaromatic hydrocarbons (PAHs) are more soluble in the presence of biosurfactants. Phenanthrene had the highest solubility among the tested PAHs, which further increased as biosurfactant doses raised above their respective critical micelle concentrations (CMC). Furthermore, biosurfactants were able to recover 73.5-63.4% of residual oil from the sludge within their respective CMCs. Hence, selected surfactant-producing bacteria and their consortium could be useful in developing a greener and eco-sustainable way for removing crude oil pollutants from soil.

Heavy Metals, Proximate Analysis and Brine Shrimp Lethality of Vernonia amygdalina and Ocimum gratissimum Growing in Crude Oil-Rich Delta State, Nigeria

Vernonia amygdalina (VA) and Ocimum gratissimum (OG) are among the most frequently consumed vegetables in Kokori and Abraka communities of Delta State, Nigeria. However, the continuous crude oil exploration and spillages in Kokori may threaten their safety for use as food and medicine. Twelve samples of VA and OG obtained from crude oil-rich and crude oil-free communities were comparatively analysed for proximate composition, heavy metals, and cytotoxicity. Data obtained were subjected to various multivariate statistical techniques, including principal component analysis (PCA), biplot, and analysis of variance (ANOVA), to investigate the correlations between the vegetables from the different communities and the effect of crude oil exploration and spill on plant biomass. Results obtained indicate a significant difference (p < 0.05) in the proximate composition of VA and OG and higher heavy metal content for VA from the crude oil-spill Kokori. Two VA collections from Kokori were exceptionally toxic to cellular crustaceans.

Invertebrate and vertebrate predation rates in a hyperarid ecosystem following an oil spill

Extreme temperatures and scarce precipitation in deserts have led to abiotic factors often being regarded as more important than biotic ones in shaping desert communities. The presumed low biological activity of deserts is also one reason why deserts are often overlooked by conservation programs. We provide the first quantification of predation intensity from a desert ecosystem using artificial sentinel prey emulating caterpillars, a standardized monitoring tool to quantify relative predation pressure by many invertebrate and vertebrate predators. The study was conducted in a protected natural area affected by oil spills in 1975 and 2014; hence, we assessed the potential effects of oil pollution on predation rates. We found that predation was mostly due to invertebrate rather than vertebrate predators, fluctuated throughout the year, was higher at the ground level than in the tree canopy, and was not negatively affected by the oil spills. The mean predation rate per day (12.9%) was within the range found in other ecosystems, suggesting that biotic interactions in deserts ought not to be neglected and that ecologists should adopt standardized tools to track ecological functions and allow for comparisons among ecosystems.

Phytotoxicity of petroleum hydrocarbons: Sources, impacts and remediation strategies

Extraction and exploration of petroleum hydrocarbons (PHs) to satisfy the rising world population's fossil fuel demand is playing havoc with human beings and other life forms by contaminating the ecosystem, particularly the soil. In the current review, we highlighted the sources of PHs contamination, factors affecting the PHs accumulation in soil, mechanisms of uptake, translocation and potential toxic effects of PHs on plants. In plants, PHs reduce the seed germination andnutrients translocation, and induce oxidative stress, disturb the plant metabolic activity and inhibit the plant physiology and morphology that ultimately reduce plant yield. Moreover, the defense strategy in plants to mitigate the PHs toxicity and other potential remediation techniques, including the use of organic manure, compost, plant hormones, and biochar, and application of microbe-assisted remediation, and phytoremediation are also discussed in the current review. These remediation strategies not only help to remediate PHs pollutionin the soil rhizosphere but also enhance the morphological and physiological attributes of plant and results to improve crop yield under PHs contaminated soils. This review aims to provide significant information on ecological importance of PHs stress in various interdisciplinary investigations and critical remediation techniques to mitigate the contamination of PHs in agricultural soils.

Dopamine Alleviates Hydrocarbon Stress in Brassica oleracea through Modulation of Physio-Biochemical Attributes and Antioxidant Defense Systems

Hydrocarbon stress has become one of the most restrictive factors for crop choice and productivity in most parts of the world. Dopamine (DA) has positively influenced the metabolic, physiological and biochemical activities besides the growth of plants under numerous abiotic stress conditions. The current study was performed to analyze the potential of DA to alleviate hydrocarbon stress and improve growth of Brassica oleracea plants. Hydrocarbon stress in plants was induced by growing in 5% and 10% crude oil contaminated soil. Crude oil stressed plants exhibited reduced growth besides decreased level of photosynthetic pigments and gas exchange attributes. Moreover, oil stressed plants showed elevated level of hydrogen peroxide (H₂O₂), electrolyte leakage (EL), malondialdehyde (MDA) and superoxide radical (O^2-). However, exogenous application of 50, 100 and 200 μmol L^-1 DA improved photosynthesis, shoot and root dry weight of B. oleracea seedlings growing in hydrocarbon amended soil. Additionally, DA100 treatments improved non-enzymatic and enzymatic antioxidants of treated seedlings. Our results demonstrate that increased gas exchange attributes, modulation of osmoregulators and improved activity of the antioxidative enzymes alleviated hydrocarbon stress in DA supplemented B. oleracea plants. Consequently, the first time observed ameliorative role of DA in hydrocarbon stress opens a new arena for application of this dynamic biomolecule for sustainable crop production.

Microbiological Study in Petrol-Spiked Soil

The pollution of arable lands and water with petroleum-derived products is still a valid problem, mainly due the extensive works aimed to improve their production technology to reduce fuel consumption and protect engines. An example of the upgraded fuels is the BP 98 unleaded petrol with Active technology. A pot experiment was carried out in which Eutric Cambisol soil was polluted with petrol to determine its effect on the microbiological and biochemical properties of this soil. Analyses were carried out to determine soil microbiome composition-with the incubation and metagenomic methods, the activity of seven enzymes, and cocksfoot effect on hydrocarbon degradation. The following indices were determined: colony development index (CD); ecophysiological diversity index (EP); index of cocksfoot effect on soil microorganisms and enzymes (IFG); index of petrol effect on soil microorganisms and enzymes (IFP); index of the resistance of microorganisms, enzymes, and cocksfoot to soil pollution with petrol (RS); Shannon-Weaver's index of bacterial taxa diversity (H); and Shannon-Weaver's index of hydrocarbon degradation (IDH). The soil pollution with petrol was found to increase population numbers of bacteria and fungi, and Protebacteria phylum abundance as well as to decrease the abundance of Actinobacteria and Acidobacteria phyla. The cultivation of cocksfoot on the petrol-polluted soil had an especially beneficial effect mainly on the bacteria belonging to the Ramlibacter, Pseudoxanthomonas, Mycoplana, and Sphingobium genera. The least susceptible to the soil pollution with petrol and cocksfoot cultivation were the bacteria of the following genera: Kaistobacter, Rhodoplanes, Bacillus, Streptomyces, Paenibacillus, Phenylobacterium, and Terracoccus. Cocksfoot proved effective in the phytoremediation of petrol-polluted soil, as it accelerated hydrocarbon degradation and increased the genetic diversity of bacteria. It additionally enhanced the activities of soil enzymes.

Effect of Crude Oil on Growth, Oxidative Stress and Response of Antioxidative System of Two Rye (Secale cereale L.) Varieties

Rye (Secale cereale L.) is one of the most important cereal crops in Eastern and Northern Europe, showing better tolerance to environmental stress factors compared to wheat and triticale. Plant response to the crude oil-polluted soil depends on plant species, oil concentration, time of exposure, etc. The current study is aimed at investigating the growth, oxidative stress and the response of antioxidative system of two rye varieties (Krona and Valdai) cultivated on crude oil-contaminated soils at different concentrations (1.5, 3.0, 6.0, and 12.0%). Inhibition of rye growth was observed at crude oil concentrations of above 3% for above-ground plant parts and of above 1.5% for roots. A decrease in content of chlorophyll a and total chlorophylls in Krona variety was detected at 1.5% oil concentration in soil and in Valdai variety at 3% oil concentration. Compared with the control, the content of malondialdehyde was significantly increased in the Krona variety at 3% oil concentration and in Valdai variety at 6% oil concentration. The crude oil-induced oxidative stress was minimized in rye plants by the enhanced contents of low-molecular antioxidants (proline, non-protein thiols, ascorbic acid, phenolic compounds) and activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione peroxidase. The strongest positive correlation was detected between the content of malondialdehyde and contents of proline (r = 0.89–0.95, p ≤ 0.05) and phenolic compounds (r = 0.90–0.94, p ≤ 0.05) as well as superoxide dismutase activity (r = 0.81–0.90, p ≤ 0.05). Based on the results of a comprehensive analysis of growth and biochemical parameters and of the cluster analysis, Valdai variety proved to be more resistant to oil pollution. Due to this, Valdai variety is considered to be a promising rye variety for cultivation on moderately oil-polluted soils in order to decontaminate them. At the same time, it is necessary to conduct further studies aimed at investigating oil transformation processes in the soil-rye system, which would make it possible to determine the efficiency of using this cereal for soil remediation.

Phylogenetic Analysis of the Membrane Attack Complex/Perforin Domain-Containing Proteins in Gossypium and the Role of GhMACPF26 in Cotton Under Cold Stress

The membrane attack complex/perforin (MACPF) domain-containing proteins are involved in the various developmental processes and in responding to diverse abiotic stress. The function and regulatory network of the MACPF genes are rarely reported in Gossypium spp. We study the detailed identification and partial functional verification of the members of the MACPF family. Totally, 100 putative MACPF proteins containing complete MACPF domain were identified from the four cotton species. They were classified into three phylogenetic groups and underwent multifold pressure indicating that selection produced new functional differentiation. Cotton MACPF gene family members expanded mainly through the whole-genome duplication (WGD)/segmental followed by the dispersed. Expression and cis-acting elements analysis revealed that MACPFs play a role in resistance to abiotic stresses, and some selected GhMACPFs were able to respond to the PEG and cold stresses. Co-expression analysis showed that GhMACPFs might interact with valine-glutamine (VQ), WRKY, and Apetala 2 (AP2)/ethylene responsive factor (ERF) domain-containing genes under cold stress. In addition, silencing endogenous GhMACPF26 in cotton by the virus-induced gene silencing (VIGS) method indicated that GhMACPF26 negatively regulates cold tolerance. Our data provided a comprehensive phylogenetic evolutionary view of Gossypium MACPFs. The MACPFs may work together with multiple transcriptional factors and play roles in acclimation to abiotic stress, especially cold stress in cotton.

Phytosociology and antioxidant profile study for selecting potent herbs for phytoremediation of crude oil-contaminated soils

Crude oil exploration activities affect the surrounding vegetation. The present investigation deals with the study of phytosociology and biochemical profiles of the herbaceous community in the active and abandoned oil drilling sites of crude oil-explored area. For comparison, a similar investigation was also carried out in control sites where oil exploration activities were not evident. At first, a phytosociological investigation was carried out and based on the results obtained antioxidant enzyme profiles of dominant herbs were studied to understand their defense mechanism to crude oil-associated stress. A total of 69 plant species belonging to 20 families were recorded in the studied sites and the family Cyperaceae was the most dominant in the crude oil-contaminated sites. The results revealed that the plants growing near the oil-explored-contaminated sites exhibit a higher level of DPPH and H₂O₂ radical scavenging activities as compared to control plant samples. For DPPH assay, the lowest IC₅₀ value was exhibited by Cyperus rotundus which was recorded to be 31.49 and 55.31 respectively for the samples of contaminated and control sites. Again, in the case of H₂O₂ scavenging activity assay, Parthenium hysterophorus showed the lowest IC₅₀ values of 27.48 and 63.07 for the samples of contaminated and control sites respectively. As a whole, the findings confirm the superior defense mechanism of some dominant herbs of the contaminated sites that include Torenia flava, Croton bonplandianus, Eclipta alba, Cyperus rotundus, Cyperus brevifolius, and Parthenium hysterophorus and their suitability for use in phytomanagement practices.

Seed Predation on Oil-Polluted and Unpolluted Vachellia (Acacia) Trees in a Hyper-Arid Desert Ecosystem

Simple Summary

Bruchid beetles are the pests of many plant species worldwide. One or more grubs can develop inside a seed by consuming it and impairing its germination. Vachellia trees are important for preserving diverse and healthy arid ecosystems, but they are often threatened by human activities and hostile environmental conditions. Seed predation by bruchid beetles is one of the major causes of the decline in the populations of Vachellia trees in Israel. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we evaluated whether oil pollution increases seed predation rates of the seeds of Vachellia tortilis and V. raddiana. We recorded remarkably high predation rates for both species, particularly at the ground level, which suggests that conservation measures to reduce repeated infestations on fallen pods may be important to preserve these tree species. However, we found no clear evidence of a negative effect of oil pollution on seed predation, indicating that it did not increase the vulnerability of the seeds to bruchids even in trees affected by the recent oil spill.

Abstract

Acacia trees are keystone species in many arid environments, supporting high levels of plant and animal diversity. In Israel, the populations of Vachellia (formerly Acacia) tortilis (Forssk.) and V. raddiana (Savi) are declining at an alarming rate. Severe infestations by bruchid beetles (Coleoptera, Chrysomelidae) are among the major causes of seed mortality, but additional environmental stressors can reduce the defence level of the seeds, exacerbating their susceptibility to predators. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we quantified seed predation rates caused by insect granivores before and after the pods dropped to the ground. We recorded predation rates of up to 84% for both tree species, and higher predation rates at the ground level than in the canopy, suggesting that repeated infestations occur. These results reinforce the call to protect the populations of large ungulates such as gazelles, which kill the bruchids by feeding upon the pods, and promote seed germination and dispersion. We found no clear evidence of a negative effect of the oil spill on seed predation, indicating that oil pollution did not increase the vulnerability of the seeds to granivores even in trees affected by the recent oil spill.

Enhanced performance of Bacillus megaterium OSR-3 in combination with putrescine ammeliorated hydrocarbon stress in Nicotiana tabacum

Hydrocarbon stress (HS) has been causing decreased plant growth and productivity. Putrescine (Put) and growth promoting microbes are vital for plant growth and development under hydrocarbon stress. Current research work was carried out to evaluate the potential of Bacillus megaterium OSR-3 alone and in combination with Put to alleviate HS in Nicotiana tabacum (L.). The crude petroleum contaminated soil significantly reduced growth attributes of N. tabacum. B. megaterium OSR-3 inoculated plants subjected to HS exhibited improved photosynthetic rate, gas exchange characteristics, poline contents and protein level. Furthermore, bacterial inoculation enhanced the antioxidative activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in tobacco plants subjected to HS. The HS alleviation in B. megaterium OSR-3 inoculated N. tabacum can be credited to the heightened activity of antioxidative enzymes, reduction in hydrogen peroxide (H2O2) and abridged synthesis of malondialdehyde (MDA). The increased synthesis of indole acetic acid (IAA) in HS stressed N. tabacum plants treated with co-application of B. megaterium OSR-3 and Put attenuated toxicity and amplified growth of plants. Additionally, the co-application of B. megaterium OSR-3 and Put also upregulated the activity of antioxidative enzymes and induced augmented level of proline and IAA in plants under HS regimes. Current research provides novel insight into the potential and mechanism of B. megaterium OSR-3 and Put in mitigation of HS in N. tabacum plants.