Ascorbic acid and selenium nanoparticles synergistically interplay in chromium stress mitigation in rice seedlings by regulating oxidative stress indicators and antioxidant defense mechanism

Ascorbic acid (AsA) and selenium nanoparticles (SeNPs) were versatile plant growth regulators, playing multiple roles in promoting plant growth under heavy metal stresses. This study aimed to evaluate the beneficial role of individual and combined effects of AsA and SeNPs on morpho-physio-biochemical traits of rice with or without chromium (Cr) amendment. The results indicated that Cr negatively affected plant biomass, gas exchange parameters, total soluble sugar, proline, relative water contents, and antioxidant-related gene expression via increasing reactive oxygen species (MDA, H2O2, O2•-) formation, resulting in plant growth reduction. The application of AsA and SeNPs, individually or in combination, decreased the uptake and translocation of Cr in rice seedlings, increased seedlings with tolerance to Cr toxicity, and significantly improved the rice seedling growth. Most notably, AsA + SeNP treatment strengthened the antioxidative defense system through ROS quenching and Cr detoxification. The results collectively suggested that the application of AsA and SeNPs alone or in combination had the potential to alleviate Cr toxicity in rice and possibly other crop species.

Exogenously applied sodium nitroprusside alleviates nickel toxicity in maize by regulating antioxidant activities and defense-related gene expression

Nickel (Ni) stress adversely affects plant growth and biomass accumulation, posturing severe menace to crop production and food security. The current study aimed to determine the putative role of sodium nitroprusside (SNP) in mitigating Ni-induced phytotoxicity and identify the underlying defense mechanisms in maize, which are poorly understood. Our findings showed that SNP significantly augmented plant growth, biomass, and photosynthesis-related attributes (Fv/Fm, Fm, qP ETR, and ΦPSII) through diminishing Ni uptake and translocation in root and shoot tissues of maize under Ni stress conditions. In parallel, exogenous SNP substantially relieved maize seedlings from Ni-induced stress by enhancing enzymatic (SOD, CAT, and GPX) and non-enzymatic (phenol and flavonoids) antioxidant defenses and reducing oxidative stress indicators (MDA and H2 O2 ). The results revealed that SNP treatment increased the content of organic osmolyte glycine betaine and the activity of GST, concomitantly with ATP and ionic exchange capacity (including Ca2+ -ATPase and Mg2+ -ATPase), advocating its sufficiency to promote plant growth and avert Ni-induced stress in maize plants. The only exception was the production of organic acids (citric, oxalic, malic, and formic acids), which was reduced as SNP treatment relieved maize seedlings from Ni-induced oxidative damage. The application of SNP also displayed higher expression of defense- and detoxifying-related genes than in control treatments. Together, our data highlighted the mechanism involved in the amelioration of Ni toxicity by SNP; thus, suggesting a potential role of SNP in mitigating the adverse effects of Ni-contaminated soils to boost growth and yield of crop plants, that is, maize.

Nitric oxide mitigates vanadium toxicity in soybean (Glycine max L.) by modulating reactive oxygen species (ROS) and antioxidant system

Vanadium (V) induced hazardous effects posturing a serious concern on crop production as well as food security. However, the nitric oxide (NO)-mediated alleviation of V-induced oxidative stress in soybean seedlings is still unknown. Therefore, this research was designed to explore the effects of exogenous NO to mitigate the V-induced phytotoxicity in soybean plants. Our upshots disclosed that NO supplementation considerably improved the plant biomass, growth, and photosynthetic attributes by regulating the carbohydrates, and plants biochemical composition, which further improved the guard cells, and stomatal aperture of soybean leaves. Additionally, NO regulated the plant hormones, and phenolic profile which restricted the V contents absorption (65.6%), and translocation (57.9%) by maintaining the nutrient acquisition. Furthermore, it detoxified the excessive V contents, and upsurged the antioxidants defense mechanism to lower the MDA, and scavenge ROS production. The molecular analysis further verified the NO-based regulation of lipid, sugar production, and degradation as well as detoxification mechanism in the soybean seedlings. Exclusively, we elaborated very first time the behind mechanism of V-induced oxidative stress alleviation by exogenous NO, hence illustrating the NO supplementation role as a stress alleviating agent for soybean grown in V contaminated areas to elevate the crop development and production.

Gibberellic acid mitigates nickel stress in soybean by cell wall fixation and regulating oxidative stress metabolism and glyoxalase system

It is broadly known that excessive concentration of nickel (Ni) causes venomous effects on plant health as well as food security. The underlying gibberellic acid (GA) mechanism to overcome Ni-induced stress is still unclear. Our outcomes represented the potential role of gibberellic acid (GA) to boost the soybean stress tolerance mechanism against Ni toxicity. GA elevated the seed germination, plant growth, biomass indices, and photosynthetic machinery as well as relative water contents under Ni-induced stress in soybean. We found that the GA lowered the Ni uptake, and distribution in the soybean plants, as well as GA, can decrease the Ni fixation in the root cell wall by lowering the hemicelluloses content. However, it reduces the MDA level, over-generation of ROS, electrolyte leakage, and methylglyoxal contents by up-surging the level of antioxidant enzyme, and glyoxalase I and glyoxalase II activities. Furthermore, GA regulates the antioxidant-related (CAT, SOD, APX, and GSH) and phytochelatins (PCs) genes expression to sequester the excessive Ni to the vacuoles and efflux the Ni outer the cell. Hence, less Ni was translocated toward shoots. Overall, GA augmented cell wall Ni elimination, and the antioxidant defense mechanism possibly upgraded the soybean tolerance against Ni stress.

Brassinosteroid Supplementation Alleviates Chromium Toxicity in Soybean (Glycine max L.) via Reducing Its Translocation

Chromium (Cr) phytotoxicity severely inhibits plant growth and development which makes it a prerequisite to developing techniques that prevent Cr accumulation in food chains. However, little is explored related to the protective role of brassinosteroids (BRs) against Cr-induced stress in soybean plants. Herein, the morpho-physiological, biochemical, and molecular responses of soybean cultivars with/without foliar application of BRs under Cr toxicity were intensely investigated. Our outcomes deliberated that BRs application noticeably reduced Cr-induced phytotoxicity by lowering Cr uptake (37.7/43.63%), accumulation (63.92/81.73%), and translocation (26.23/38.14%) in XD-18/HD-19, plant tissues, respectively; besides, improved seed germination ratio, photosynthetic attributes, plant growth, and biomass, as well as prevented nutrient uptake inhibition under Cr stress, especially in HD-19 cultivar. Furthermore, BRs stimulated antioxidative defense systems, both enzymatic and non-enzymatic, the compartmentalization of ion chelation, diminished extra production of reactive oxygen species (ROS), and electrolyte leakage in response to Cr-induced toxicity, specifically in HD-19. In addition, BRs improved Cr stress tolerance in soybean seedlings by regulating the expression of stress-related genes involved in Cr accumulation, and translocation. Inclusively, by considering the above-mentioned biomarkers, foliar spray of BRs might be considered an effective inhibitor of Cr-induced damages in soybean cultivars, even in Cr polluted soil.

Seed Priming with Spermine Mitigates Chromium Stress in Rice by Modifying the Ion Homeostasis, Cellular Ultrastructure and Phytohormones Balance

Chromium (Cr) is an important environmental constraint effecting crop productivity. Spermine (SPM) is a polyamine compound regulating plant responses to abiotic stresses. However, SPM-mediated tolerance mechanisms against Cr stress are less commonly explored in plants. Thus, current research was conducted to explore the protective mechanisms of SPM (0.01 mM) against Cr (100 µM) toxicity in two rice cultivars, CY927 (sensitive) and YLY689 (tolerant) at the seedling stage. Our results revealed that, alone, Cr exposure significantly reduced seed germination, biomass and photosynthetic related parameters, caused nutrient and hormonal imbalance, desynchronized antioxidant enzymes, and triggered oxidative damage by over-accretion of reactive oxygen species (ROS), malondialdehyde (MDA) and electrolyte leakage in both rice varieties, with greater impairments in CY927 than YLY689. However, seed priming with SPM notably improved or reversed the above-mentioned parameters, especially in YLY689. Besides, SPM stimulated the stress-responsive genes of endogenous phytohormones, especially salicylic acid (SA), as confirmed by the pronounced transcript levels of SA-related genes (OsPR1, OsPR2 and OsNPR1). Our findings specified that SPM enhanced rice tolerance against Cr toxicity via decreasing accumulation of Cr and markers of oxidative damage (H₂O₂, O₂^•− and MDA), improving antioxidant defense enzymes, photosynthetic apparatus, nutrients and phytohormone balance.

Evaluation of Green Super Rice Lines for Agronomic and Physiological Traits under Salinity Stress

Rice (Oryza sativa) is an important staple food crop worldwide, especially in east and southeast Asia. About one-third of rice cultivated area is under saline soil, either natural saline soils or irrigation with brackish water. Salinity stress is among the devastating abiotic stresses that not only affect rice growth and crop productivity but also limit its cultivation area globally. Plants adopt multiple tolerance mechanisms at the morphological, physiological, and biochemical levels to tackle salinity stress. To identify these tolerance mechanisms, this study was carried out under both a controlled glass house as well as natural saline field conditions using 22 green super rice (GSR) lines along with two local varieties (“IRRI 6 and Kissan Basmati”). Several morpho-physiological and biochemical parameters along with stress-responsive genes were used as evaluation criteria under normal and salinity stress conditions. Correlation and Principal Component Analysis (PCA) suggested that shoot-related parameters and the salt susceptible index (SSI) can be used for the identification of salt-tolerant genotypes. Based on Agglomerative Hierarchical Cluster (AHC) analysis, two saline-tolerant (“S19 and S20”) and saline-susceptible (“S3 and S24”) lines were selected for further molecular evaluation. Quantitative RT-PCR was performed, and results showed that expression of 1-5-phosphoribosyl -5-5-phosphoribosyl amino methylidene amino imidazole-4-carboxamide isomerase, DNA repair protein recA, and peptide transporter PTR2 related genes were upregulated in salt-tolerant genotypes, suggesting their potential role in salinity tolerance. However, additional validation using reverse genetics approaches will further confirm their specific role in salt tolerance. Identified saline-tolerant lines in this study will be useful genetic resources for future salinity breeding programs.

Seed priming with brassinosteroids alleviates aluminum toxicity in rice via improving antioxidant defense system and suppressing aluminum uptake

Brassinosteroids (BRs) are growth-promoting hormones that exhibit high biological activities across various plant species. BRs shield plants against various abiotic stresses. In the present study, the effect of BRs against aluminum (Al) toxicity was investigated through seed priming with 24-epibrassinolide (0.01 μM) in two different rice cultivars. BRs application was found effective in confronting plants from Al toxicity (400 μM). The rice seeds primed with BRs showed enhancement in seed germination energy, germination percentage, root and shoot length, as well as fresh and dry weight under Al-absence and Al-stressed conditions as compared to water-priming. Especially under Al stress, BRs priming promoted the growth of rice seedlings more obviously. Al toxicity significantly increased the Al contents in seedling root and shoot, as well as the MDA concentration, H₂O₂ production, and the activities of antioxidative enzymes including ascorbate peroxidase, catalase, and peroxidase. Meanwhile, the photosynthetic pigments of seedling reduced under Al stress. When compared to sensitive cultivar (CY-927), these modifications were more obvious in the tolerant variety (YLY-689). Surprisingly, BRs were able to alleviate the Al injury by lowering MDA and H₂O₂ level and increasing antioxidant activities and photosynthetic pigments under Al stress. The results on antioxidant activities were further validated by gene expression study of SOD-Cu-Zn, SOD-Fe₂, CATa, CATb, APX02, and APX08. It suggested that BRs were responsible for the mitigation of Al stress in rice seedlings by inducing antioxidant activities with an effective response to other seed growth parameters and reduced Al uptake under induced metal stress.

An optimized method for RNA extraction from the polyurethane oligomer degrading strain Pseudomonas capeferrum TDA1 growing on aromatic substrates such as phenol and 2,4-diaminotoluene

Bacterial degradation of xenobiotic compounds is an intense field of research already for decades. Lately, this research is complemented by downstream applications including Next Generation Sequencing (NGS), RT-PCR, qPCR, and RNA-seq. For most of these molecular applications, high-quality RNA is a fundamental necessity. However, during the degradation of aromatic substrates, phenolic or polyphenolic compounds such as polycatechols are formed and interact irreversibly with nucleic acids, making RNA extraction from these sources a major challenge. Therefore, we established a method for total RNA extraction from the aromatic degrading Pseudomonas capeferrum TDA1 based on RNAzol® RT, glycogen and a final cleaning step. It yields a high-quality RNA from cells grown on TDA1 and on phenol compared to standard assays conducted in the study. To our knowledge, this is the first report tackling the problem of polyphenolic compound interference with total RNA isolation in bacteria. It might be considered as a guideline to improve total RNA extraction from other bacterial species.

Seed Priming with Brassinosteroids Alleviates Chromium Stress in Rice Cultivars via Improving ROS Metabolism and Antioxidant Defense Response at Biochemical and Molecular Levels

This research was performed to explore the vital role of seed priming with a 0.01 µM concentration of brassinosteroids (EBL) to alleviate the adverse effects of Cr (100 µM) in two different rice cultivars. Seed priming with EBL significantly enhanced the germination attributes (germination percentage, germination energy, germination index, and vigor index, etc.), photosynthetic rate as well as plant growth (shoot and root length including the fresh and dry weight) under Cr toxicity as compared to the plants primed with water. Cr toxicity induced antioxidant enzyme activities (SOD, POD, CAT, and APX) and ROS level (MDA and H₂O₂ contents) in both rice cultivars; however, a larger increment was observed in YLY-689 (tolerant) than CY-927 (sensitive) cultivar. EBL application stimulatingly increased antioxidant enzyme activities to scavenge ROS production under Cr stress. The gene expression of SOD and POD in EBL-primed rice plants followed a similar increasing trend as observed in the case of enzymatic activities of SOD and POD compared to water-primed rice plants. Simultaneously, Cr uptake was observed to be significantly higher in the water-primed control compared to plants primed with EBL. Moreover, Cr uptake was significant in YLY-689 compared to CY-927. In ultra-structure studies, it was observed that EBL priming relieved the rice plants from sub-cellular damage. Conclusively, our research indicated that seed priming with EBL could be adopted as a promising strategy to enhance rice growth by copping the venomous effect of Cr.

Physiological, ultrastructural, biochemical, and molecular responses of glandless cotton to hexavalent chromium (Cr6+) exposure

Glandless cotton can be grown to obtain cotton seeds free of toxic gossypol for use as both food and feed. However, they are not grown normally due to their lesser productivity and higher susceptibility to biotic stress. Great attention has been paid to biotic stresses rather than abiotic stresses on glandless cotton. Chromium (Cr) is a common pollutant of soil and considered a serious threat to plants due to its adverse effects on different functions. Although numerous studies are available on the toxicity of Cr⁶⁺ in various plants. However, its adverse effects and mechanism of toxicity in glandless cotton can seldom be found in the literature. This study examined the Cr⁶⁺ effect on glandless cotton in comparison to glanded cotton. Four pairs of glanded and glandless cotton near-isogenic lines (NILs) were exposed to different doses (0, 10, 50, and 100 μM/L) of Cr⁶⁺ for seven days, and biochemical, physiological, molecular, and ultrastructure changes were observed, which were significantly affected by Cr⁶⁺ at high concentrations in all NILs. The effect of Cr⁶⁺ on ionic contents shows the same trend in glanded and glandless NILs except for manganese (Mn²⁺) that show inhibition in glandless (ZMS-12w and Coker-312w) and enhance in the glanded NIL (ZMS-17). The gene expression of superoxide dismutase (SOD) and peroxidase (POD) revealed similar trends as enzyme activities in glandless NILs. The principal component analysis (PCA) and Agglomerative hierarchical clustering (AHC) results of all NILs from morpho-physiological traits, cluster ZMS-16, and ZMS-17 into Cr⁶⁺ sensitive group. While the glandless NILs have the potential to cope with the Cr toxicity by increasing the antioxidant enzyme activity and their gene expression. This study also revealed that Cr⁶⁺ tolerance in cotton is genotypic and has an independent mechanism in the root that not related to low gossypol.

Comparative analysis and innovation of a simple and rapid method for high-quality RNA and DNA extraction of kiwifruit

RNA and DNA extraction is a requirement for the study of gene expression and has an increasingly important role in genetic studies of all fleshy fruits. RNA and DNA extraction is difficult in kiwifruit due to the significant amount of polysaccharides and polyphenols compounds. So far, no commercial kit has been developed specifically for high-quality RNA and DNA extraction in kiwifruit and the common protocols for RNA extraction have poor yields. This study developed a new protocol for high quality RNA extraction in Actinidia deliciosa. According to the results, the average yield of RNA extraction of fruit and leaf of A. deliciosa was ∼2180.7 ng/μl (∼545.175 μg/g FW) and ∼3424.9 ng/μl (∼856.225 μg/g FW), respectively with A₂₆₀/A₂₈₀ between 1.95 to 2.07 and A₂₆₀/A₂₃₀ higher than 2 indicating high RNA purity. While the averages yield of RNA extraction using previous methods from kiwifruit and leaf was 23 μg/g FW and 527 μg/g FW, respectively. Also, the average yields of genomic DNA from kiwifruit ranged from 52 to 98 ng/μl with A₂₆₀/A₂₃₀ between 0.60 to 1.64 and A₂₆₀/A₂₈₀ between 1.40 to 1.48. To our knowledge, this is the first report of a highly efficient and rapid method of RNA and DNA extraction in kiwifruit which can be used for a broad spectrum of the all fleshy fruits.

A rapid and efficient SDS-based RNA isolation protocol from different tissues of coffee

Isolation of high-quality RNA from coffee is challenging because of high level of polysaccharides, polyphenols and other secondary metabolites. In the present study, a rapid and efficient RNA extraction protocol from different tissues of coffee was optimized. Sufficiently high quality and quantity (225.6-454.8 µg/g) of RNA was obtained by using the optimized protocol. The presence of two distinct bands of 28S rRNA and 18S rRNA in agarose gel proved the intactness of the RNA samples. The average spectrophotometric values of the isolated RNA ranged from 1.96 to 2.02 (A_260/280) and 1.95 to 2.14 (A_260/230), indicating the high quality of RNA devoid of polyphenols, polysaccharides and protein contamination. In the optimized protocol, addition of PVPP to the extraction buffer and a brief incubation of samples at 65 °C and subsequent purification with potassium acetate resulted in good-quality RNA isolation. The suitability of RNA for downstream processing was confirmed by PCR amplification with cytochrome c oxidase gene-specific primers. The amplification of a single 392 bp fragment using cDNA and 1.5 kb fragment using genomic DNA samples confirmed the absence of DNA contamination. The present protocol is rapid and yielded good quality and quantity of RNA suitable for functional genomics studies.

High quality RNA extraction from Maqui berry for its application in next-generation sequencing

Maqui berry (Aristotelia chilensis) is a native Chilean species that produces berries that are exceptionally rich in anthocyanins and natural antioxidants. These natural compounds provide an array of health benefits for humans, making them very desirable in a fruit. At the same time, these substances also interfere with nucleic acid preparations, making RNA extraction from Maqui berry a major challenge. Our group established a method for RNA extraction of Maqui berry with a high quality RNA (good purity, good integrity and higher yield). This procedure is based on the adapted CTAB method using high concentrations of PVP (4 %) and β-mercaptoethanol (4 %) and spermidine in the extraction buffer. These reagents help to remove contaminants such as polysaccharides, proteins, phenols and also prevent the oxidation of phenolic compounds. The high quality of RNA isolated through this method allowed its uses with success in molecular applications for this endemic Chilean fruit, such as differential expression analysis of RNA-Seq data using next generation sequencing (NGS). Furthermore, we consider that our method could potentially be used for other plant species with extremely high levels of antioxidants and anthocyanins.