Effect of methyl jasmonate and GA3 on canola (Brassica napus L.) growth, antioxidants activity, and nutrient concentration cultivated in salt-affected soils.

Salinity stress is a significant challenge in agricultural production. When soil contains high salts, it can adversely affect plant growth and productivity due to the high concentration of soluble salts in the soil water. To overcome this issue, foliar applications of methyl jasmonate (MJ) and gibberellic acid (GA3) can be productive amendments. Both can potentially improve the plant's growth attributes and flowering, which are imperative in improving growth and yield. However, limited literature is available on their combined use in canola to mitigate salinity stress. That's why the current study investigates the impact of different levels of MJ (at concentrations of 0.8, 1.6, and 3.2 mM MJ) and GA3 (0GA3 and 5 mg/L GA3) on canola cultivated in salt-affected soils. Applying all the treatments in four replicates. Results indicate that the application of 0.8 mM MJ with 5 mg/L GA3 significantly enhances shoot length (23.29%), shoot dry weight (24.77%), number of leaves per plant (24.93%), number of flowering branches (26.11%), chlorophyll a (31.44%), chlorophyll b (20.28%) and total chlorophyll (27.66%) and shoot total soluble carbohydrates (22.53%) over control. Treatment with 0.8 mM MJ and 5 mg/L GA3 resulted in a decrease in shoot proline (48.17%), MDA (81.41%), SOD (50.59%), POD (14.81%) while increase in N (10.38%), P (15.22%), and K (8.05%) compared to control in canola under salinity stress. In conclusion, 0.8 mM MJ + 5 mg/L GA3 can improve canola growth under salinity stress. More investigations are recommended at the field level to declare 0.8 mM MJ + 5 mg/L GA3 as the best amendment for alleviating salinity stress in different crops.

The fungus Acremonium alternatum enhances salt stress tolerance by regulating host redox homeostasis and phytohormone signaling.

While endophytic fungi offer promising avenues for bolstering plant resilience against abiotic stressors, the molecular mechanisms behind this biofortification remain largely unknown. This study employed a multifaceted approach, combining plant physiology, proteomic, metabolomic, and targeted hormonal analyses to illuminate the early response of Brassica napus to Acremonium alternatum during the nascent stages of their interaction. Notably, under optimal growth conditions, the initial reaction to fungus was relatively subtle, with no visible alterations in plant phenotype and only minor impacts on the proteome and metabolome. Interestingly, the identified proteins associated with the Acremonium response included TUDOR 1, Annexin D4, and a plastidic K+ efflux antiporter, hinting at potential processes that could counter abiotic stressors, particularly salt stress. Subsequent experiments validated this hypothesis, showcasing significantly enhanced growth in Acremonium-inoculated plants under salt stress. Molecular analyses revealed a profound impact on the plant's proteome, with over 50% of salt stress response proteins remaining unaffected in inoculated plants. Acremonium modulated ribosomal proteins, increased abundance of photosynthetic proteins, enhanced ROS metabolism, accumulation of V-ATPase, altered abundances of various metabolic enzymes, and possibly promoted abscisic acid signaling. Subsequent analyses validated the accumulation of this hormone and its enhanced signaling. Collectively, these findings indicate that Acremonium promotes salt tolerance by orchestrating abscisic acid signaling, priming the plant's antioxidant system, as evidenced by the accumulation of ROS-scavenging metabolites and alterations in ROS metabolism, leading to lowered ROS levels and enhanced photosynthesis. Additionally, it modulates ion sequestration through V-ATPase accumulation, potentially contributing to the observed decrease in chloride content.

Functional and regulatory diversity of homeobox-leucine zipper transcription factors BnaHB6 under dehydration and salt stress in Brassica napus L.

The plant-specific homeodomain-leucine zipper I subfamily is involved in the regulation of various biological processes, particularly growth, development and stress response. In the present study, we characterized four BnaHB6 homologues from Brassica napus. All BnaHB6 proteins have transcriptional activation activity. Structural and functional data indicate the complex role of BnaHB6 genes in regulating biological processes, with some functions conserved and others diverged. Transcriptional analyzes revealed that they are induced in a similar manner in different tissues but show different expression patterns in response to stress and circadian rhythm. Only the BnaA09HB6 and BnaC08HB6 genes are expressed under dehydration and salt stress, and in darkness. The partial transcriptional overlap of BnaHB6s with the evolutionarily related genes BnaHB5 and BnaHB16 was also observed. Transgenic Arabidopsis thaliana plants expressing a single proBnaHB6::GUS partially confirmed the expression results. Bioinformatic analysis allowed the identification of TF-binding sites in the BnaHB6 promoters that may control their expression under stress and circadian rhythm. ChIP-qPCR analysis revealed that BnaA09HB6 and BnaC08HB6 bind directly to the promoters of the target genes BnaABF4 and BnaDREB2A. Comparison of their expression patterns in the WT plants and the bnac08hb6 mutant showed that BnaC08HB6 positively regulates the expression of the BnaABF4 and BnaDREB2A genes under dehydration and salt stress. We conclude that four BnaHB6 homologues have distinct functions in response to stress despite high sequence similarity, possibly indicating different binding preferences with BnaABF4 and BnaDREB2A. We hypothesize that BnaC08HB6 and BnaA09HB6 function in a complex regulatory network under stress.

Deciphering proteomic mechanisms explaining the role of glutathione as an aid in improving plant fitness and tolerance against cadmium-toxicity in Brassica napus L.

Cadmium (Cd) hazard is a serious limitation to plants, soils and environments. Cd-toxicity causes stunted growth, chlorosis, necrosis, and plant yield loss. Thus, ecofriendly strategies with understanding of molecular mechanisms of Cd-tolerance in plants is highly demandable. The Cd-toxicity caused plant growth retardation, leaf chlorosis and cellular damages, where the glutathione (GSH) enhanced plant fitness and Cd-toxicity in Brassica through Cd accumulation and antioxidant defense. A high-throughput proteome approach screened 4947 proteins, wherein 370 were differently abundant, 164 were upregulated and 206 were downregulated. These proteins involved in energy and carbohydrate metabolism, CO2 assimilation and photosynthesis, signal transduction and protein metabolism, antioxidant defense response, heavy metal detoxification, cytoskeleton and cell wall structure, and plant development in Brassica. Interestingly, several key proteins including glutathione S-transferase F9 (A0A078GBY1), ATP sulfurylase 2 (A0A078GW82), cystine lyase CORI3 (A0A078FC13), ferredoxin-dependent glutamate synthase 1 (A0A078HXC0), glutaredoxin-C5 (A0A078ILU9), glutaredoxin-C2 (A0A078HHH4) actively involved in antioxidant defense and sulfur assimilation-mediated Cd detoxification process confirmed by their interactome analyses. These candidate proteins shared common gene networks associated with plant fitness, Cd-detoxification and tolerance in Brassica. The proteome insights may encourage breeders for enhancing multi-omics assisted Cd-tolerance in Brassica, and GSH-mediated hazard free oil seed crop production for global food security.

Veterinary antibiotics differ in phytotoxicity on oilseed rape grown over a wide range of concentrations.

Residues of veterinary antibiotics are a worldwide problem of increasing concern due to their persistence and diverse negative effects on organisms, including crops, and limited understanding of their phytotoxicity. Therefore, this study aimed to compare the phytotoxic effects of veterinary antibiotics tetracycline (TC) and ciprofloxacin (CIP) applied in a wide range of concentrations on model plant oilseed rape (Brassica napus). Overall phytotoxicity of 1-500 mg kg-1 of TC and CIP was investigated based on morphological, biochemical, and physiological plant response. Photosystem II (PSII) performance was suppressed by TC even under environmentally relevant concentration (1 mg kg-1), with an increasing effect proportionally to TC concentration in soil. In contrast, CIP was found to be more phytotoxic than TC when applied at high concentrations, inducing a powerful oxidative burst, impairment of photosynthetic performance, collapse of antioxidative protection and sugar metabolism, and in turn, complete growth retardation at 250 and 500 mg kg-1 CIP treatments. Results of our study suggest that TC and CIP pollution do not pose a significant risk to oilseed rapes in many little anthropogenically affected agro-environments where TC or CIP concentrations do not exceed 1 mg kg-1; however, intensive application of manure with high CIP concentrations (more than 50 mg kg-1) might be detrimental to plants and, in turn, lead to diminished agricultural production and a potential risk to human health.

Application of prohexadione-calcium priming affects Brassica napus L. seedlings by regulating morph-physiological characteristics under salt stress.

Salinity stress imposes severe constraints on plant growth and development. Here, we explored the impacts of prohexadione-calcium (Pro-Ca) on rapeseed growth under salt stress. We designed a randomized block design pot experiment using two rapeseed varieties, 'Huayouza 158R' and 'Huayouza 62'. We conducted six treatments, S0: non-primed + 0 mM NaCl, Pro-Ca+S0: Pro-Ca primed + 0 mM NaCl, S100: non-primed + 100 mM NaCl, Pro-Ca+S100: Pro-Ca primed + 100 mM NaCl, S150: non-primed + 150 mM NaCl, Pro-Ca+S150: Pro-Ca primed + 150 mM NaCl. The morphophysiological characteristics, and osmoregulatory and antioxidant activities were compared for primed and non-primed varieties. Our data analysis showed that salt stress induced morph-physiological traits and significantly reduced the antioxidant enzyme activities in both rapeseed varieties. The Pro-Ca primed treatment significantly improved seedlings, root, and shoot morphological traits and accumulated more dry matter biomass under salt stress. Compared to Huayouza 158R, Huayouza 62 performed better with the Pro-Ca primed treatment. The Pro-Ca primed treatment significantly enhanced chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and actual photochemical quantum efficiency (ФPSII). Furthermore, the Pro-Ca primed treatment also improved ascorbic acid (ASA) content, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity, and stimulated the accumulation of soluble proteins. These findings strongly suggested that the Pro-Ca primed treatment may effectively counteract the negative impacts of salinity stress by regulating the morph-physiological and antioxidant traits.

Effects of antibiotics on secondary metabolism and oxidative stress in oilseed rape seeds.

Cruciferae brassica oilseed rape is the third largest oilseed crop in the world and the first in China, as well as a fertilizer-dependent crop. With the increased application of organic fertilizers from livestock manure in agricultural production in recent years, the resulting antibiotic pollution and its ecological health effects have attracted widespread attention. In this study, typical tetracycline and sulfonamide antibiotics tetracycline (TC) and sulfamethoxazole (SMZ) were used to investigate the effects of antibiotics on rapeseed quality and oxidative stress at the level of secondary metabolism on the basis of examining the effects of the two drugs on the growth of soil-cultivated rapeseed seedlings. The results showed that both plant height and biomass of rapeseed seedlings were significantly suppressed and ROS were significantly induced in rapeseed by exposure to high concentrations (2.5 mg/kg) of TC and SMZ. Carotenoids, tocopherols, and SOD enzymes were involved in the oxidative stress response to scavenge free radicals in rapeseed, but phenolic acids and flavonoids contents were decreased, which reduced the quality of the seeds to some extent.

Combined application of zinc and iron-lysine and its effects on morpho-physiological traits, antioxidant capacity and chromium uptake in rapeseed (Brassica napus L.).

Environmental contamination of chromium (Cr) has gained substantial consideration worldwide because of its high levels in the water and soil. A pot experiment using oil seed crop (rapeseed (Brassica napus L.)) grown under different levels of tannery wastewater (0, 33, 66 and 100%) in the soil using the foliar application of zinc (Zn) and iron (Fe)-lysine (lys) has been conducted. Results revealed that a considerable decline in the plant growth and biomass elevates with the addition of concentrations of tannery wastewater. Maximum decline in plant height, number of leaves, root length, fresh and dry biomass of root and leaves were recorded at the maximum level of tannery wastewater application (100%) compared to the plants grown without the addition of tannery wastewater (0%) in the soil. Similarly, contents of carotenoid and chlorophyll, gas exchange parameters and activities of various antioxidants (superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)) were also reduced significantly (P < 0.05) with the increasing concentration of tannery wastewater (33, 66 and 100%) in the soil. In addition, a combined application of Zn and Fe-lys reduced the accumulation and uptake of toxic Cr, while boosting the uptake of essential micronutrients such as Zn and Fe in different tissues of the plants. Results concluded that exogenous application of micronutrients chelated with amino acid successfully mitigate Cr stress in B. napus. Under field conditions, supplementation with these micronutrient-chelated amino acids may be an effective method for alleviating metal stress in other essential seed crops.

Potential roles for pattern molecule of PAMP-triggered immunity in improving crop cold tolerance.

KEY MESSAGE: The application of flagellin 22 (flg22), the most widely studied PAMP, enhance crop cold tolerance. ICE1-CBF pathway and SA signaling is involved in the alleviation of cold injury by flg22 treatment. Pathogen infection cross-activates cold response and increase cold tolerance of host plants. However, it is not possible to use the infection to increase cold tolerance of field plants. Here flagellin 22 (flg22), the most widely studied PAMP (pathogen-associated molecular patterns), was used to mimic the pathogen infection to cross-activate cold response. Flg22 treatment alleviated the injury caused by freezing in Arabidopsis, oilseed and tobacco. In Arabidopsis, flg22 activated the expression of immunity and cold-related genes. Moreover, the flg22 induced alleviation of cold injury was lost in NahG transgenic line (SA-deficient), sid2-2 and npr1-1 mutant plants, and flg22-induced expression of cold tolerance-related genes, which indicating that salicylic acid signaling pathway is required for the alleviation of cold injury by flg22 treatment. In short flg22 application can be used to enhance cold tolerance in field via a salicylic acid-depended pathway.

Role of beneficial microbes with nitrogen and phosphorous levels on canola productivity / Papel de microbes benéficos em associação com níveis de nitrogênio e fósforo na produtividade de canola

A research was conducted to evaluate the impact of various nitrogen and phosphorus levels along with beneficial microbes to enhance canola productivity. The research was carried out at Agronomy Research Farm, The University of Agriculture Peshawar in winter 2016-2017. The experiment was conducted in randomized complete block factorial design. The study was comprised of three factors including nitrogen (60, 120 and 180 kg ha-¹), phosphorous (70, 100 and 130 kg ha-¹) and beneficial microbes (with and without BM). A control treatment with no N, P and BM was also kept for comparison. Application of beneficial microbes significantly increased pods plant, seed pod, seed filling duration, 1000 seed weight, biological yield and seed yield as compared to control plots. Nitrogen applied at the rate of 180 kg ha-¹ increased pods plant-¹, seed pod, seed filling duration, seed weight, biological yield and seed yield. Maximum pods plant-¹, seed pod, early seed filling, heavier seed weight, biological yield, seed yield, and harvest index were observed in plots treated with 130 kg.ha-¹ phosphorous. As comparison, the combine treated plots have more pods plant-¹, seeds pod-¹, seed filling duration, heaviest seeds, biological yield, seed yield and harvest index as compared to control plots. It is concluded that application of beneficial microbes with N and P at the rate of 180 kg ha-¹ and 130 kg ha-¹, respectively, increased yield and its attributes for canola.

Uma pesquisa foi realizada para avaliar o impacto de vários níveis de nitrogênio e fósforo, juntamente com micróbios benéficos, para aumentar a produtividade da canola. A pesquisa foi realizada no inverno de 2016-17 no Agronomy Research Farm, Universidade de Agricultura do Peshawar. O experimento foi conduzido por planejamento fatorial aleatorizado em blocos. O estudo focou-se em três fatores, incluindo o teor de nitrogênio, N, (60, 120 e 180 kg.ha-¹), o teor de fósforo, P, (70, 100 e 130 kg ha-¹) e a presença de micróbios benéficos (com BM e sem BM). Para fins de comparação, um tratamento controle sem N, P e BM também foi incluído no estudo. A aplicação de micróbios benéficos aumentou significativamente as vagens das plantas e de sementes, a duração do enchimento das sementes, o peso de 1000 sementes, o rendimento biológico e o rendimento de sementes em comparação com os resultados do controle. O nitrogênio aplicado na taxa de 180 kg ha-¹ aumentou as vagens por planta, vagem, duração do enchimento, peso da semente, rendimento biológico e rendimento de sementes. Vagens máximas por planta, vagem, enchimento precoce de sementes, peso maior de semente, rendimento biológico, rendimento de sementes e índice de colheita foram observados em parcelas tratadas com 130 kg.ha-¹ de fósforo. Em comparação aos blocos cultivados de controle, os blocos cultivados tratados combinados têm mais vagens por planta e sementes por vagem, maior duração do enchimento das sementes, maior número de sementes mais pesadas e maior rendimento biológico, rendimento de sementes e índice de colheita. Conclui-se que a aplicação de micróbios benéficos junto com N e P nas doses de 180 kg ha-¹ e 130 kg ha-¹, respectivamente, aumentou a produtividade e atributos de produtividade para a canola.

Exploration of physiological and biochemical processes of canola with exogenously applied fertilizers and plant growth regulators under drought stress.

Environmental stresses may alter the nutritional profile and economic value of crops. Chemical fertilizers and phytohormones are major sources which can enhance the canola production under stressful conditions. Physio-biochemical responses of canola altered remarkably with the use of nitrogen/phosphorus/potassium (N/P/K) fertilizers and plant growth regulators (PGRs) under drought stress. The major aim of current study was to evaluate nutritional quality and physio-biochemical modulation in canola (Brassica napus L.) from early growth to seed stage with NPK and PGRs in different water regimes. To monitor biochemical and physiological processes in canola, two season field experiment was conducted as spilt plot under randomized complete block design (RCBD) with four treatments (Control, Chemical fertilizers [N (90 kg/ha), P and K (45 kg ha-1)], PGRs; indole acetic acid (IAA) 15g ha-1, gibberellic acid (GA3) 15g ha-1 and the combination of NPK and PGRs] under different irrigations regimes (60, 100, 120, 150 mm evaporations). Water stress enhanced peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), polyphenol oxidase (PPO), soluble sugar, malondialdehyde (MDA), proline contents as well as leaf temperature while substantially reduced leaf water contents (21%), stomatal conductance (50%), chlorophyll contents (10-67%), membrane stability index (24%) and grain yield (30%) of canola. However, the combined application of NPK and PGR further increased the enzymatic antioxidant pool, soluble sugars, along with recovery of leaf water contents, chlorophyll contents, stomatal conductance and membrane stability index but decreased the proline contents and leaf temperature at different rate of evaporation. There is positive interaction of applied elicitors to the water stress in canola except leaf area. The outcomes depicted that the combination of NPK with PGRs improved the various morpho-physiological as well as biochemical parameters and reduced the pressure of chemical fertilizers cost about 60%. It had also reduced the deleterious effect of water limitation on the physiology and grain yield and oil contents of canola in field experiments.

Bisphenol A-A Dangerous Pollutant Distorting the Biological Properties of Soil.

Bisphenol A (BPA), with its wide array of products and applications, is currently one of the most commonly produced chemicals in the world. A narrow pool of data on BPA-microorganism-plant interaction mechanisms has stimulated the following research, the aim of which has been to determine the response of the soil microbiome and crop plants, as well as the activity of soil enzymes exposed to BPA pressure. A range of disturbances was assessed, based on the activity of seven soil enzymes, an abundance of five groups of microorganisms, and the structural diversity of the soil microbiome. The condition of the soil was verified by determining the values of the indices: colony development (CD), ecophysiological diversity (EP), the Shannon-Weaver index, and the Simpson index, tolerance of soil enzymes, microorganisms and plants (TIBPA), biochemical soil fertility (BA21), the ratio of the mass of aerial parts to the mass of plant roots (PR), and the leaf greenness index: Soil and Plant Analysis Development (SPAD). The data brought into sharp focus the adverse effects of BPA on the abundance and ecophysiological diversity of fungi. A change in the structural composition of bacteria was noted. Bisphenol A had a more beneficial effect on the Proteobacteria than on bacteria from the phyla Actinobacteria or Bacteroidetes. The microbiome of the soil exposed to BPA was numerously represented by bacteria from the genus Sphingomonas. In this object pool, the highest fungal OTU richness was achieved by the genus Penicillium, a representative of the phylum Ascomycota. A dose of 1000 mg BPA kg-1 d.m. of soil depressed the activity of dehydrogenases, urease, acid phosphatase and ß-glucosidase, while increasing that of alkaline phosphatase and arylsulfatase. Spring oilseed rape and maize responded significantly negatively to the soil contamination with BPA.

Effects of seed priming treatments on the germination and development of two rapeseed (Brassica napus L.) varieties under the co-influence of low temperature and drought.

The present study was performed to evaluate the effects of seed priming. This was done by soaking the seeds of two rapeseed cultivars, namely, ZY15 (tolerant to low temperature and drought) and HY49 (sensitive to low temperature and drought), for 12 h in varying solutions: distilled water, 138 mg/L salicylic acid (SA), 300 mg/L gibberellic acid (GA), 89.4 mg/L sodium nitroprusside (SNP), 3000 mg/L calcium chloride (CaCl2), and 30 mg/L abscisic acid (ABA). Primed and non-primed seeds were left to germinate at 15°C and -0.15 MPa (T15W15) and at 25°C and 0 MPa (T25W0), respectively. The results showed that SA, GA, SNP, CaCl2, and ABA significantly improved the germination potential (GP), germination rate (GR), germination index (GI), stem fresh weight (SFW), stem dry weight (SDW), root length (RL), stem length (SL), and seed vigor index (SVI) under T15W15. For ZY15 seeds under T25W0, GA, SNP, CaCl2, and ABA priming reduced the average germination time (96% after 5 days) compared to that of the control (88% after 5 days). For ZY15 seeds under T15W15, SA, SNP, CaCl2, and ABA priming, with respect to the control and water-treated groups, shortened the average germination time (92% after 5 days) compared to that of the control (80% after 5 days). For HY49 seeds under T25W0, GA, SNP, CaCl2, and ABA priming reduced the average germination time (92% after 5 days) compared to that of the control (85% after 5 days). Similarly, for HY49 seeds under T15W15, GA priming shortened the average germination time (89% after 5 days) compared to that of the control (83% after 5 days). These priming agents increased the net photosynthesis, stomatal conductivity, and transpiration rate of rape seedlings under conditions of low temperature and drought stress, while also decreasing intercellular carbon dioxide (CO2) concentrations. Additionally, SA, GA, SNP, CaCl2, and ABA increased superoxide dismutase concentrations (SOD) and ascorbic peroxidase (APX) activities of rape seedlings under stress conditions, while decreasing catalase (CAT) and peroxidase (POD) activities in ZY15 seedlings. In HY49, which is sensitive to low temperature and drought, all priming solutions, except for SNP, led to an increase in SOD activity levels and a decrease in CAT activity levels. Overall, SA, GA, SNP, and CaCl2 increased the concentrations of indoleacetic acid (IAA), GA, ABA, and cytokinin (CTK) in seedlings under stress conditions. Moreover, compared to SA, CaCl2, and ABA, GA (300 mg/L) and SNP (300 mol/L) showed improved priming effects for ZY15 and HY49 under stress conditions.

Nanoceria seed priming enhanced salt tolerance in rapeseed through modulating ROS homeostasis and α-amylase activities.

BACKGROUND: Salinity is a big threat to agriculture by limiting crop production. Nanopriming (seed priming with nanomaterials) is an emerged approach to improve plant stress tolerance; however, our knowledge about the underlying mechanisms is limited. RESULTS: Herein, we used cerium oxide nanoparticles (nanoceria) to prime rapeseeds and investigated the possible mechanisms behind nanoceria improved rapeseed salt tolerance. We synthesized and characterized polyacrylic acid coated nanoceria (PNC, 8.5 ± 0.2 nm, -43.3 ± 6.3 mV) and monitored its distribution in different tissues of the seed during the imbibition period (1, 3, 8 h priming). Our results showed that compared with the no nanoparticle control, PNC nanopriming improved germination rate (12%) and biomass (41%) in rapeseeds (Brassica napus) under salt stress (200 mM NaCl). During the priming hours, PNC were located mostly in the seed coat, nevertheless the intensity of PNC in cotyledon and radicle was increased alongside with the increase of priming hours. During the priming hours, the amount of the absorbed water (52%, 14%, 12% increase at 1, 3, 8 h priming, respectively) and the activities of α-amylase were significantly higher (175%, 309%, 295% increase at 1, 3, 8 h priming, respectively) in PNC treatment than the control. PNC primed rapeseeds showed significantly lower content of MDA, H2O2, and •O2- in both shoot and root than the control under salt stress. Also, under salt stress, PNC nanopriming enabled significantly higher K+ retention (29%) and significantly lower Na+ accumulation (18.5%) and Na+/K+ ratio (37%) than the control. CONCLUSIONS: Our results suggested that besides the more absorbed water and higher α-amylase activities, PNC nanopriming improves salt tolerance in rapeseeds through alleviating oxidative damage and maintaining Na+/K+ ratio. It adds more knowledge regarding the mechanisms underlying nanopriming improved plant salt tolerance.

Two Auxinic Herbicides Affect Brassica napus Plant Hormone Levels and Induce Molecular Changes in Transcription.

With the introduction of the new auxinic herbicide halauxifen-methyl into the oilseed rape (Brassica napus) market, there is a need to understand how this new molecule interacts with indigenous plant hormones (e.g., IAA) in terms of crop response. The aim of this study was to investigate the molecular background by using different growth conditions under which three different auxinic herbicides were administered. These were halauxifen-methyl (Hal), alone and together with aminopyralid (AP) as well as picloram (Pic). Three different hormone classes were determined, free and conjugated indole-3-acetic acid (IAA), aminocyclopropane carboxylic acid (ACC) as a precursor for ethylene, and abscisic acid (ABA) at two different temperatures and growth stages as well as over time (2-168 h after treatment). At 15 °C growth temperature, the effect was more pronounced than at 9 °C, and generally, the younger leaves independent of the developmental stage showed a larger effect on the alterations of hormones. IAA and ACC showed reproducible alterations after auxinic herbicide treatments over time, while ABA did not. Finally, a transcriptome analysis after treatment with two auxinic herbicides, Hal and Pic, showed different expression patterns. Hal treatment leads to the upregulation of auxin and hormone responses at 48 h and 96 h. Pic treatment induced the hormone/auxin response already after 2 h, and this continued for the other time points. The more detailed analysis of the auxin response in the datasets indicate a role for GH3 genes and genes encoding auxin efflux proteins. The upregulation of the GH3 genes correlates with the increase in conjugated IAA at the same time points and treatments. Also, genes for were found that confirm the upregulation of the ethylene pathway.

Exogenous melatonin regulates chromium stress-induced feedback inhibition of photosynthesis and antioxidative protection in Brassica napus cultivars.

KEY MESSAGE: Melatonin is an early player in chromium stress response in canola plants; it promotes ROS scavenging and chlorophyll stability, modulates PSII stability and regulates feedback inhibition of photosynthesis conferring chromium tolerance. The development of heavy metals, especially chromium (Cr)-tolerant cultivars is mainly constrained due to poor knowledge of the mechanism behind Cr stress tolerance. In the present study, two Brassica napus contrasting cultivars Ac-Excel and DGL were studied for Cr stress tolerance by using chlorophyll a fluorescence technique and biochemical attributes with and without melatonin (MT) treatments. Cr stress significantly reduced the PSII and PSI efficiency, biomass accumulation, proline content and antioxidant enzymes in both the cultivars. The application of MT minimized the oxidative stress, as revealed via a lower level of reactive oxygen species (ROS) synthesis (H2O2 and OH-). Enhanced enzymatic activities of important antioxidants (SOD, APX, CAT, POD), proline and total soluble protein contents under MT application play an effective role in the regulation of multiple transcriptional pathways involved in oxidative stress responses. Higher NPQ and Y(NPQ) observed in Cr stress tolerant cv Ac-Excel, indicating that the MT-treated tolerant cultivar had better ability to protect PSII under Cr stress by increasing heat dissipation as photo-protective component of NPQ. Reduced PSI efficiency along with increased donor end limitation of PSI in both canola cultivars further confirmed the lower PSII activity and electron transport from PSII. The Cr content was higher in cv. DGL as compared to (that in Ac-Excel). The application of MT significantly decreased the Cr content in leaves of both cultivars. Overall, MT-induced Cr stress tolerance in canola cultivars can be related to improved PSII activity, Y(NPQ), and antioxidant potential and these physiological attributes can effectively be used to select cultivars for Cr stress tolerance.

Evolution and functional diversity of lipoxygenase (LOX) genes in allotetraploid rapeseed (Brassica napus L.).

Lipoxygenase (LOX, EC 1.13.11.12) is a non-haeme iron-containing dioxygenase family that catalyzes the oxygenation of polyunsaturated fatty acids into bio-functionally fatty acid diverse (oxylipins) and plays vital role in plant growth and development and responses to abiotic and biotic stresses. Though LOX genes have been studied in many plant species, their roles in Brassicaceae species are still unknown. Here, a set of 14, 18, and 33 putative LOX genes were identified in Brassica rapa, Brassica oleracea and Brassica napus (allotetraploid rapeseed), respectively, which could be divided into 9-LOX (LOX1/5), 13-LOX type I (LOX3/4/6), and type II (LOX2) subgroups. There was an expansion of LOX2 orthologous genes in Brassicaceae. Most of the LOX genes are intron rich and conserved in gene structure, and the LOX proteins all have the conserved lipoxygenase and PLAT/LH2 domain. Ka/Ks ratio revealed that the majority of LOXs underwent purifying selection in Brassicaceae. The light-, ABA-, MeJA-related cis-elements and MYB-binding sites in the promoters of BnaLOXs were the most abundant. BnaLOXs displayed different spatiotemporal expression patterns and various abiotic/biotic stress responsive expression patterns. BnaLOX1/5 were slightly or no response to phytohormones and abiotic stresses. BnaLOX3/4/6 predominantly express in roots and were strongly up-regulated by salinity and PEG treatments, and BnaLOX3/4 were the methyl jasmonate (MeJA) and salicylic acid (SA) early response genes and strongly induced by infection of Sclerotinia sclerotiorum; while the BnaLOX2 members predominantly express in stamens, were MeJA and SA continuous response genes and strongly repressed by cold, heat and waterlogging treatments in leaves. Our results are useful for understanding the biological functions of the BnaLOX genes in allotetraploid rapeseed.

The Expression Characteristics of NPF Genes and Their Response to Vernalization and Nitrogen Deficiency in Rapeseed.

The NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY (NPF) genes, initially characterized as nitrate or peptide transporters in plants, are involved in the transport of a large variety of substrates, including amino acids, nitrate, auxin (IAA), jasmonates (JAs), abscisic acid (ABA) and gibberellins (GAs) and glucosinolates. A total of 169 potential functional NPF genes were excavated in Brassica napus, and they showed diversified expression patterns in 90 different organs or tissues based on transcriptome profile data. The complex time-serial expression changes were found for most functional NPF genes in the development process of leaves, silique walls and seeds, which indicated that the expression of Brassica napus NPF (BnaNPF) genes may respond to altered phytohormone and secondary metabolite content through combining with promoter element enrichment analysis. Furthermore, many BnaNPF genes were detected to respond to vernalization with two different patterns, and 20 BnaNPF genes responded to nitrate deficiency. These results will provide useful information for further investigation of the biological function of BnaNPF genes for growth and development in rapeseed.

Proteome Changes Reveal the Protective Roles of Exogenous Citric Acid in Alleviating Cu Toxicity in Brassica napus L.

Citric acid (CA), as an organic chelator, plays a vital role in alleviating copper (Cu) stress-mediated oxidative damage, wherein a number of molecular mechanisms alter in plants. However, it remains largely unknown how CA regulates differentially abundant proteins (DAPs) in response to Cu stress in Brassica napus L. In the present study, we aimed to investigate the proteome changes in the leaves of B. L. seedlings in response to CA-mediated alleviation of Cu stress. Exposure of 21-day-old seedlings to Cu (25 and 50 µM) and CA (1.0 mM) for 7 days exhibited a dramatic inhibition of overall growth and considerable increase in the enzymatic activities (POD, SOD, CAT). Using a label-free proteome approach, a total of 6345 proteins were identified in differentially treated leaves, from which 426 proteins were differentially expressed among the treatment groups. Gene ontology (GO) and KEGG pathways analysis revealed that most of the differential abundance proteins were found to be involved in energy and carbohydrate metabolism, photosynthesis, protein metabolism, stress and defense, metal detoxification, and cell wall reorganization. Our results suggest that the downregulation of chlorophyll biosynthetic proteins involved in photosynthesis were consistent with reduced chlorophyll content. The increased abundance of proteins involved in stress and defense indicates that these DAPs might provide significant insights into the adaptation of Brassica seedlings to Cu stress. The abundances of key proteins were further verified by monitoring the mRNA expression level of the respective transcripts. Taken together, these findings provide a potential molecular mechanism towards Cu stress tolerance and open a new route in accelerating the phytoextraction of Cu through exogenous application of CA in B. napus.

Exogenous 3,3'-Diindolylmethane Improves Vanadium Stress Tolerance in Brassica napus Seedling Shoots by Modulating Antioxidant Enzyme Activities.

3,3'-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, in this study we investigated whether exogenous DIM could improve the vanadium tolerance of AV Garnet. We performed the following experiments: seed germination assessment, dry weight assessment, cell viability assay, chlorophyll content assay, malondialdehyde (MDA) assay, conjugated diene (CD) content assay, hydrogen peroxide (H2O2) content assay, superoxide (O2-) content determination, methylglyoxal (MG) content determination, hydroxyl radical (·OH) concentration determination, ascorbate peroxidase (APX) activity assay, superoxide dismutase (SOD) activity assay, glyoxalase I (Gly I) activity assay, glutathione S-transferase (GST) activity assay and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for vanadium content determination. Under vanadium stress, exogenous DIM increased the seed germination percentage, shoot dry weight, cell viability and chlorophyll content. Exogenous DIM also led to a decrease in MDA, CD, H2O2, O2-, MG and ·OH, under vanadium stress in the shoots. Furthermore, DIM application led to an increase in the enzymatic activities of APX, SOD, Gly I and GST under vanadium stress. Interestingly, under vanadium stress, DIM treatment did not alter vanadium content in B. napus shoots. Our results indicate that exogenous application of DIM can improve B. napus seedling shoot growth and biomass under vanadium stress by priming the antioxidant enzymes via reactive oxygen species (ROS) signaling.