Alleviation effect of GR24, a strigolactone analogue, on low-nitrogen stress in Malus baccata seedlings.

To investigate the efficacy of foliar application of GR24, a strigolactone analogue, in alleviating low-nitrogen stress in Malus baccata, we applied GR24 with different concentrations (0, 1, 5, 10, and 20 µmol·L-1) to leaves of plants under low nitrogen stress. We evaluated the changes in photosynthetic characteristics of leaves, reactive oxygen metabolism, and nitrogen assimilation in roots. The results showed that shoot biomass of seedling significantly decreased and root-shoot ratio increased under low-nitrogen stress. The chlorophyll contents decreased, the carotenoid content increased, and the photosynthetic activity decreased. The activities of superoxide dismutase and catalase enzymes in roots changed little, while the activities of peroxidase and ascorbic acid peroxidase enzymes, along with the levels of soluble sugar, free proline, and reactive oxygen species showed a significant increase, and the soluble protein content decreased. The NO3- content in roots decreased, the NH4+ content increased, while activities of nitrate reductase and glutamine synthase decreased. Compared to the control group without GR24 application, foliar sprays of 10 and 20 µmol·L-1 GR24 under both normal and low-nitrogen increased biomass and root-shoot ratio to varying degrees. Additionally, GR24 application increased chlorophyll content, photosynthesis indices (net photosynthetic rate, transpiration rate and stomatal conductance), and fluorescence (maximum photochemical efficiency of PSⅡ and quantum yield of electron transfer per unit area) performance parameters, as well as the contents of osmotic regulation substances (soluble protein, soluble sugar, and free proline) and glutamine synthase activity. Application of 10 and 20 µmol·L-1 GR24 under low-nitrogen stress decreased carotenoid, reactive oxygen species, and NH4+ contents, while increased the activities of antioxidases and key enzymes in nitrogen metabolism (nitrate reductase and glutamine synthase) and NO3- content. The 10 µmol·L-1 GR24 treatment was the most effective in alleviating low nitrogen stress, which has potential for application in apple orchards with low nitrogen soil.

Disclosing the molecular basis of salinity priming in olive trees using proteogenomic model discovery.

Plant responses to salinity are becoming increasingly understood, however, salt priming mechanisms remain unclear, especially in perennial fruit trees. Herein, we showed that low-salt pre-exposure primes olive (Olea europaea) plants against high salinity stress. We then performed a proteogenomic study to characterize priming responses in olive roots and leaves. Integration of transcriptomic and proteomic data along with metabolic data revealed robust salinity changes that exhibit distinct or overlapping patterns in olive tissues, among which we focused on sugar regulation. Using the multi-crossed -omics data set, we showed that major differences between primed and nonprimed tissues are mainly associated with hormone signaling and defense-related interactions. We identified multiple genes and proteins, including known and putative regulators, that reported significant proteomic and transcriptomic changes between primed and nonprimed plants. Evidence also supported the notion that protein post-translational modifications, notably phosphorylations, carbonylations and S-nitrosylations, promote salt priming. The proteome and transcriptome abundance atlas uncovered alterations between mRNA and protein quantities within tissues and salinity conditions. Proteogenomic-driven causal model discovery also unveiled key interaction networks involved in salt priming. Data generated in this study are important resources for understanding salt priming in olive tree and facilitating proteogenomic research in plant physiology.

Effects of silicon application on leaf structure and physiological characteristics of Glycyrrhiza uralensis Fisch. and Glycyrrhiza inflata Bat. under salt treatment.

BACKGROUND: Soil salinization leads to a significant decline in crop yield and quality, including licorice, an important medicinal cash crop. Studies have proofed that the application of exogenous silicon can significantly improve the ability of licorice to resist salt stress, however, few studies concentrated on the effects of foliar silicon application on the morphology, physiological characteristics, and anatomical structure of licorice leaves under salt stress. In this study, the effects of Si (K2SiO3) on the structural and physiological characteristics of Glycyrrhiza uralensis Fisch. and G. inflata Bat. leaves under different salt concentrations (medium- and high-salt) were studied. RESULTS: Compared with the control (without salt), the plant height, total dry weight, leaf area, leaf number, relative water content, xylem area, phloem area, ratio of palisade to spongy tissue, gas exchange parameters, and photosynthetic pigment content of both licorice varieties were significantly reduced under high-salt (12S) conditions. However, the thickness of the leaf, palisade tissue, and spongy tissue increased significantly. Applying Si to the leaf surface increased the area of the vascular bundle, xylem, and parenchyma of the leaf's main vein, promoted water transportation, enhanced the relative leaf water content, and reduced the decomposition of photosynthetic pigments. These changes extended the area of photosynthesis and promoted the production and transportation of organic matter. G. uralensis had a better response to Si application than did G. inflata. CONCLUSIONS: In conclusion, foliar application of Si can improve water absorption, enhance photosynthesis, improve photosynthetic capacity and transpiration efficiency, promote growth and yield, and alleviate the adverse effects of salt stress on the leaf structure of the two kinds of licorice investigated.

Enhancement of Vindoline and Catharanthine Accumulation, Antioxidant Enzymes Activities, and Gene Expression Levels in Catharanthus roseus Leaves by Chitooligosaccharides Elicitation.

Catharanthus roseus (L.) G. Don is a plant belonging to the genus Catharanthus of the Apocynaceae family. It contains more than one hundred alkaloids, of which some exhibit significant pharmacological activities. Chitooligosaccharides are the only basic aminooligosaccharides with positively charged cations in nature, which can regulate plant growth and antioxidant properties. In this study, the leaves of Catharanthus roseus were sprayed with chitooligosaccharides of different molecular weights (1 kDa, 2 kDa, 3 kDa) and different concentrations (0.01 µg/mL, 0.1 µg/mL, 1 µg/mL and 10 µg/mL). The fresh weights of its root, stem and leaf were all improved after chitooligosaccharides treatments. More importantly, the chitooligosaccharides elicitor strongly stimulated the accumulation of vindoline and catharanthine in the leaves, especially with the treatment of 0.1 µg/mL 3 kDa chitooligosaccharides, the contents of them were increased by 60.68% and 141.54%, respectively. Furthermore, as the defensive responses, antioxidant enzymes activities (catalase, glutathione reductase, ascorbate peroxidase, peroxidase and superoxide dismutase) were enhanced under chitooligosaccharides treatments. To further elucidate the underlying mechanism, qRT-PCR was used to investigate the genes expression levels of secologanin synthase (SLS), strictosidine synthase (STR), strictosidine glucosidase (SGD), tabersonine 16-hydroxylase (T16H), desacetoxyvindoline-4-hydroxylase (D4H), deacetylvindoline-4-O-acetyltransferase (DAT), peroxidase 1 (PRX1) and octadecanoid-responsive Catharanthus AP2-domain protein 3 (ORCA3). All the genes were significantly up-regulated after chitooligosaccharides treatments, and the transcription abundance of ORCA3, SLS, STR, DAT and PRX1 reached a maximal level with 0.1 µg/mL 3 kDa chitooligosaccharides treatment. All these results suggest that spraying Catharanthus roseus leaves with chitooligosaccharides, especially 0.1 µg/mL of 3 kDa chitooligosaccharides, may effectively improve the pharmaceutical value of Catharanthus roseus.

Transcriptome analysis of Tamarix ramosissima leaves in response to NaCl stress.

Halophyte Tamarix ramosissima. Lcdcb (T. ramosissima) are known as the representative of Tamarix plants that are widely planted in salinized soil. However, molecular mechanisms towards salt tolerance and adaptation are largely rare. In this study, we carried out RNA-sequence and transcriptome analysis of T. ramosissima in response to NaCl stress, screened differentially expressed genes (DEGs) and further verified by qRT-PCR. Results showed that 105702 unigenes were spliced from the raw data of transcriptome sequencing, where 54238 unigenes were retrieved from KEGG, KOG, NR, and SwissProt. After 48 hours of NaCl treatment, the expression levels of 6374 genes were increased, and 5380 genes were decreased in leaves. After 168 hours, the expression levels of 3837 genes were up-regulated and 7808 genes were down-regulated. In particular, 8 transcription factors annotated to the KEGG Pathway were obtained, involving the WRKY and bZIP transcription family. In addition, KEGG pathway annotation showed that expression of 39 genes involved in ROS scavenging mechanisms were significantly changed, in which 21 genes were up-regulated and 18 genes were down-regulated after 48 hours as well as 15 genes were up-regulated and 24 genes were down-regulated after 168h. Simultaneously, the enzyme activities of SOD and POD were significantly enhanced under NaCl treatment, but the enzyme activity of CAT was not significantly enhanced. Moreover, WRKY, MYB and bZIP may participate in the process of salt resistance in T. ramosissima. This study provides gene resources and a theoretical basis for further molecular mechanisms of salt tolerance in T. ramosissima.

Physiological and Epigenetic Reaction of Barley (Hordeum vulgare L.) to the Foliar Application of Silicon under Soil Salinity Conditions.

Soil salinity is an important environmental factor affecting physiological processes in plants. It is possible to limit the negative effects of salt through the exogenous application of microelements. Silicon (Si) is widely recognized as an element improving plant resistance to abiotic and biotic stresses. The aim of the research was to determine the impact of foliar application of Si on the photosynthetic apparatus, gas exchange and DNA methylation of barley (Hordeum vulgare L.) grown under salt stress. Plants grown under controlled pot experiment were exposed to sodium chloride (NaCl) in the soil at a concentration of 200 mM, and two foliar applications of Si were made at three concentrations (0.05%, 0.1% and 0.2%). Measurements were made of relative chlorophyll content in leaves (CCl), gas exchange parameters (Ci, E, gs, and PN), and selected chlorophyll fluorescence parameters (Fv/Fm, Fv/F0, PI and RC/ABS). Additionally, DNA methylation level based on cytosine methylation within the 3'CCGG 5' sequence was analyzed. Salinity had a negative effect on the values of the parameters examined. Exogenous application of Si by spraying leaves increased the values of the measured parameters in plants. Plants treated with NaCl in combination with the moderate (0.1%) and highest (0.2%) dose of Si indicated the lowest methylation level. Decrease of methylation implicated with activation of gene expression resulted in better physiological parameters observed in this group of barley plants.

Fungicidal properties of ginger (Zingiber officinale) essential oils against Phytophthora colocasiae.

Recently, plant essential oils (EOs) have attracted special attention in plant disease control and food preservation. Since ancient times, essential oils extracted from plants have exhibited many biological characteristics, especially antimicrobial properties. Recent studies have described the potentials of EOs and derivatives to inhibit the growth and reproduction of microorganisms, mainly in response of overwhelming concerns of consumers about food safety. In the context of returning to nature, with the advancement of science and technology and improved living standards, people have begun to seek solutions for food hygiene without chemical additives. Therefore, biological pesticides and plant-oriented chemicals have received special attention from scientists because they are environmentally friendly and nonhazardous, sustainable, and effective alternatives against many noxious phytopathogens. Present study is intended to appraise the fungicidal properties of ginger EOs to combat leaf blight disease of taro, which threatens global taro production. Farmers often hinge on extremely toxic synthetic fungicides to manage diseases, but the residual effects and resistance of chemicals are unavoidable. The microwave-assisted hydrodistillation method was used for ginger EOs extraction and an FTIR (ATR) spectrometer was used to evaluate their chemical composition and citral was identified as most abundant compound (89.05%) in oil. The pathogen isolated from lesions of diseased taro plants was identified as Phytophthora colocasiae and used as test fungus in the present study. Ginger EO was evaluated in-vitro for antifungal properties against mycelium growth, sporangium production, zoospore germination, leaf, and corm necrosis inhibition. Repeated experiments have shown that the concentration of ginger essential oil (1250 ppm) proved to be the lowest dose to obtain 100% inhibition of fungal growth and spore germination, sporangia formation and leaf necrosis assessment. These results are derived from this fungal species and a hypothesis that involves further research on other plant pathogens to demonstrate the overall potency of essential oils. This study references the easy, economic, and environmental management and control of plant diseases using essential oils and byproducts.

Effect of zinc nanoparticles seed priming and foliar application on the growth and physio-biochemical indices of spinach (Spinacia oleracea L.) under salt stress.

Salt stress is the major risk to the seed germination and plant growth via affecting physiological and biochemical activities in plants. Zinc nanoparticles (ZnNPs) are emerged as a key agent in regulating the tolerance mechanism in plants under environmental stresses. However, the tolerance mechanisms which are regulated by ZnNPs in plants are still not fully understood. Therefore, the observation was planned to explore the role of ZnNPs (applied as priming and foliar) in reducing the harmful influence of sodium chloride (NaCl) stress on the development of spinach (Spinacia oleracea L.) plants. Varying concentrations of ZnNPs (0.1%, 0.2% & 0.3%) were employed to the spinach as seed priming and foliar, under control as well as salt stress environment. The alleviation of stress was observed in ZnNPs-applied spinach plants grown under salt stress, with a reduced rise in the concentration hydrogen peroxide, melondialdehyde and anthocyanin contents. A clear decline in soluble proteins, chlorophyll contents, ascorbic acid, sugars, and total phenolic contents was observed in stressed conditions. Exogenous ZnNPs suppressed the NaCl generated reduction in biochemical traits, and progress of spinach plants. However, ZnNPs spray at 0.3% followed by priming was the most prominent treatment in the accumulation of osmolytes and the production of antioxidant molecules in plants.

Overexpression of the Aldehyde Dehydrogenase Gene ZmALDH Confers Aluminum Tolerance in Arabidopsis thaliana.

Aluminum (Al) toxicity is the main factor limiting plant growth and the yield of cereal crops in acidic soils. Al-induced oxidative stress could lead to the excessive accumulation of reactive oxygen species (ROS) and aldehydes in plants. Aldehyde dehydrogenase (ALDH) genes, which play an important role in detoxification of aldehydes when exposed to abiotic stress, have been identified in most species. However, little is known about the function of this gene family in the response to Al stress. Here, we identified an ALDH gene in maize, ZmALDH, involved in protection against Al-induced oxidative stress. Al stress up-regulated ZmALDH expression in both the roots and leaves. The expression of ZmALDH only responded to Al toxicity but not to other stresses including low pH and other metals. The heterologous overexpression of ZmALDH in Arabidopsis increased Al tolerance by promoting the ascorbate-glutathione cycle, increasing the transcript levels of antioxidant enzyme genes as well as the activities of their products, reducing MDA, and increasing free proline synthesis. The overexpression of ZmALDH also reduced Al accumulation in roots. Taken together, these findings suggest that ZmALDH participates in Al-induced oxidative stress and Al accumulation in roots, conferring Al tolerance in transgenic Arabidopsis.

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.

Air pollution from gas refinery through contamination with various elements disrupts semiarid Zagros oak (Quercus brantii Lindl.) forests, Iran.

Soils and oak trees (Quercus brantii Lindl.) in Zagros forests are suffering from the air pollution caused by the Ilam Gas Refinery. Thus, for the first time, we investigated the contamination level of sulfur and trace elements in these ecosystems. Sampling of soil and tree leaves was carried out in different seasons of 2019 and at different distances from the gas refinery. The results showed that soils and leaves at the various distances compared with control distance (10,000 m) were more affected by the gas refinery. Distance from the pollution source and physicochemical properties of soils were the main factors affecting contamination of soil elements contents. The soils with pollution load indices (PLI) of 4.54 were in the highly polluted category. Sulfur was at highly polluted category in soils and were highly enriched in trees. The trees mainly absorbed studied elements via their aerial organs. Our findings indicated that oak trees with the highest value of metal accumulation index are influence tools for monitoring various elements in the polluted air produced by the gas refinery. It is recommended that the ecosystem components near the refinery be studied to accurately evaluate disorders in the food chain.

Nitrogen application and differences in leaf number retained after topping affect the tobacco (Nicotiana tabacum) transcriptome and metabolome.

BACKGROUND: Agronomic treatments such as the application of nitrogen fertilizer and topping (removal of the inflorescence and top leaves) cause substantial changes in plant metabolism. To explore these changes, we conducted comparative transcriptomic and metabolomic analyses of leaves collected from four positions along the stem on plants exposed to two nitrogen doses and with different numbers of leaves retained after topping in tobacco (Nicotiana tabacum). RESULTS: We identified 13,330 unique differentially expressed genes and 32 differentially abundant metabolites. Through RNA-seq and WGCNA analyze, we constructed 2 co-expression networks (green and blue) highly correlation to N application and leaf number retained, predicted a hub gene NtGER3 may play an important role in N metabolism related to amino acid (cysteine) through CK pathway in tobacco leaves, NtARFs may participated in modulating the auxin signal and N in bottom leaves and NtRAP2.12 as key gene involved in N regulation by ethylene pathway. What's more, our data prove C/N transformation and balance affect the "source - flow - sink" redistribution and remobilization in tobacco during growth and development process. CONCLUSIONS: Overall, this comparative transcriptomics study provides novel insight into the complex molecular mechanisms underlying plant responses to different levels of nitrogen application and the number of leaves remaining after topping in plants.

Preparation, characterization and application of poly(lactic acid)/corn starch/eucalyptus leaf essential oil microencapsulated active bilayer degradable film.

This study aimed to develop a composite bilayer film based on corn starch (CS)/polylactic acid (PLA). The film had a hydrophobic outer layer and an absorbent inner layer. A natural bioactive substance was incorporated into the inner layer, namely, eucalyptus essential oil microcapsules (EOM). This allowed most of the bioactive substance to be released inside the storage environment. The effects of different amounts of EOM on the physical, mechanical, antioxidant, and antimicrobial properties of the films were investigated. Based on the results of scanning electron microscopy (SEM), the addition of 10-15 mL/100 mL of EOM could be uniformly distributed in the film. The addition of less than 15 mL/100 mL of EOM to the film improved its tensile strength, barrier properties, and elongation at break. The addition of too much EOM led to cracks in the film. The addition of EOM also greatly improved the antioxidant and antibacterial properties of the bilayer film. The best performance was obtained when the added amount was 15 mL/100 mL. Films with the best overall properties were used for preserving Agaricus bisporus. In preservation experiments, this film inhibited the respiration rate of A. bisporus, slowed down the consumption of organic matter, and maintained its moisture content. Compared with other cling films, the shelf life of A. bisporus was greatly extended.

Transcriptome analysis of Kentucky bluegrass subject to drought and ethephon treatment.

Kentucky bluegrass (Poa pratensis L.) is an excellent cool-season turfgrass utilized widely in Northern China. However, turf quality of Kentucky bluegrass declines significantly due to drought. Ethephon seeds-soaking treatment has been proved to effectively improve the drought tolerance of Kentucky bluegrass seedlings. In order to investigate the effect of ethephon leaf-spraying method on drought tolerance of Kentucky bluegrass and understand the underlying mechanism, Kentucky bluegrass plants sprayed with and without ethephon are subjected to either drought or well watered treatments. The relative water content and malondialdehyde conent were measured. Meanwhile, samples were sequenced through Illumina. Results showed that ethephon could improve the drought tolerance of Kentucky bluegrass by elevating relative water content and decreasing malondialdehyde content under drought. Transcriptome analysis showed that 58.43% transcripts (254,331 out of 435,250) were detected as unigenes. A total of 9.69% (24,643 out of 254,331) unigenes were identified as differentially expressed genes in one or more of the pairwise comparisons. Differentially expressed genes due to drought stress with or without ethephon pre-treatment showed that ethephon application affected genes associated with plant hormone, signal transduction pathway and plant defense, protein degradation and stabilization, transportation and osmosis, antioxidant system and the glyoxalase pathway, cell wall and cuticular wax, fatty acid unsaturation and photosynthesis. This study provides a theoretical basis for revealing the mechanism for how ethephon regulates drought response and improves drought tolerance of Kentucky bluegrass.

Exogenous salicylic acid-induced drought stress tolerance in wheat (Triticum aestivum L.) grown under hydroponic culture.

Wheat is an important cereal crop, which is adversely affected by water deficit stress. The effect of induced stress can be reduced by the application of salicylic acid (SA). With the objective to combat drought stress in wheat, an experiment was conducted in greenhouse under hydroponic conditions. The treatments consisted of (a) no drought (DD0 = 0 MPa), mild drought (DD1 = -0.40 MPa) and severe drought (DD2 = -0.60 MPa) by applying PEG-8000, (b) two contrasting wheat varieties Barani-17 (drought tolerant) and Anaj-17 (drought-sensitive), and (c) foliar treatments of salicylic acid (0, 50 mM, 75 mM, and 100 mM). Evaluation of wheat plants regarding biochemical, physiological, and morphological attributes were rendered after harvesting of plants. Statistically, maximum shoot and root fresh and dry weights (18.77, 11.15 and 1.99, 1.81 g, respectively) were recorded in cultivar Barani-17 under no drought condition with the application of SA (100 mM). While, minimum shoot and root fresh and dry weights (6.65, 3.14 and 0.73, 0.61 g, respectively) were recorded in cultivar Anaj-2017 under mild drought stress without SA application. The maximum shoot length (68.0 cm) was observed in cultivar Barani-2017 under no drought condition with the application of SA (100 mM). While, maximum root length (59.67 cm) was recorded in cultivar Anaj-17 under moderate drought stress without application of SA. Further, minimum shoot length (28.67 cm) was recorded in Anaj-17 under moderate drought stress without SA application. Minimum root length (38.67 cm) was recorded in cultivar Barani-17 under no drought condition without SA application. Furthermore, maximum physio-biochemical traits, including membrane stability index (MSI), chlorophyl content, photosynthetic rates, stomatal conductance, antioxidant enzymatic activities and relative water content (RWC) were found highest in cultivar Barani-17 under no drought stress and SA application at 100 mM. However, minimum values of these traits were recorded in cultivar Anaj-17 under severe drought stress without SA application. Our results also demonstrated that under severe drought, application of SA at 100 mM significantly increased leaf nitrogen (N), phosphrus (P) and potassium (K) contents and cultivar Barani-17 demonstrated significantly higher values than Anaj-17. The obtained results also indicated that the cultivation of wheat under drought stress conditions noticeably declines the morphological, physiological, and biochemical attributes of the plants. However, the exogenous application of SA had a positive impact on wheat crop for enhancing its productivity.

Carbon nanotube biocompatibility in plants is determined by their surface chemistry.

BACKGROUND: Agriculture faces significant global challenges including climate change and an increasing food demand due to a growing population. Addressing these challenges will require the adoption of transformative innovations into biotechnology practice, such as nanotechnology. Recently, nanomaterials have emerged as unmatched tools for their use as biosensors, or as biomolecule delivery vehicles. Despite their increasingly prolific use, plant-nanomaterial interactions remain poorly characterized, drawing into question the breadth of their utility and their broader environmental compatibility. RESULTS: Herein, we characterize the response of Arabidopsis thaliana to single walled carbon nanotube (SWNT) exposure with two different surface chemistries commonly used for biosensing and nucleic acid delivery: oligonucleotide adsorbed-pristine SWNTs, and polyethyleneimine-SWNTs loaded with plasmid DNA (PEI-SWNTs), both introduced by leaf infiltration. We observed that pristine SWNTs elicit a mild stress response almost undistinguishable from the infiltration process, indicating that these nanomaterials are well-tolerated by the plant. However, PEI-SWNTs induce a much larger transcriptional reprogramming that involves stress, immunity, and senescence responses. PEI-SWNT-induced transcriptional profile is very similar to that of mutant plants displaying a constitutive immune response or treated with stress-priming agrochemicals. We selected molecular markers from our transcriptomic analysis and identified PEI as the main cause of this adverse reaction. We show that PEI-SWNT response is concentration-dependent and, when persistent over time, leads to cell death. We probed a panel of PEI variant-functionalized SWNTs across two plant species and identified biocompatible SWNT surface functionalizations. CONCLUSIONS: While SWNTs themselves are well tolerated by plants, SWNTs surface-functionalized with positively charged polymers become toxic and produce cell death. We use molecular markers to identify more biocompatible SWNT formulations. Our results highlight the importance of nanoparticle surface chemistry on their biocompatibility and will facilitate the use of functionalized nanomaterials for agricultural improvement.

Identification of Phytaspase Interactors via the Proximity-Dependent Biotin-Based Identification Approach.

Proteolytic enzymes are instrumental in various aspects of plant development, including senescence. This may be due not only to their digestive activity, which enables protein utilization, but also to fulfilling regulatory functions. Indeed, for the largest family of plant serine proteases, subtilisin-like proteases (subtilases), several members of which have been implicated in leaf and plant senescence, both non-specific proteolysis and regulatory protein processing have been documented. Here, we strived to identify the protein partners of phytaspase, a plant subtilase involved in stress-induced programmed cell death that possesses a characteristic aspartate-specific hydrolytic activity and unusual localization dynamics. A proximity-dependent biotin identification approach in Nicotiana benthamiana leaves producing phytaspase fused to a non-specific biotin ligase TurboID was employed. Although the TurboID moiety appeared to be unstable in the apoplast environment, several intracellular candidate protein interactors of phytaspase were identified. These were mainly, though not exclusively, represented by soluble residents of the endoplasmic reticulum, namely endoplasmin, BiP, and calreticulin-3. For calreticultin-3, whose gene is characterized by an enhanced expression in senescing leaves, direct interaction with phytaspase was confirmed in an in vitro binding assay using purified proteins. In addition, an apparent alteration of post-translational modification of calreticultin-3 in phytaspase-overproducing plant cells was observed.

Comparative transcriptomic and metabolic profiling provides insight into the mechanism by which the autophagy inhibitor 3-MA enhances salt stress sensitivity in wheat seedlings.

BACKGROUND: Salt stress hinders plant growth and production around the world. Autophagy induced by salt stress helps plants improve their adaptability to salt stress. However, the underlying mechanism behind this adaptability remains unclear. To obtain deeper insight into this phenomenon, combined metabolomics and transcriptomics analyses were used to explore the coexpression of differentially expressed-metabolite (DEM) and gene (DEG) between control and salt-stressed wheat roots and leaves in the presence or absence of the added autophagy inhibitor 3-methyladenine (3-MA). RESULTS: The results indicated that 3-MA addition inhibited autophagy, increased ROS accumulation, damaged photosynthesis apparatus and impaired the tolerance of wheat seedlings to NaCl stress. A total of 14,759 DEGs and 554 DEMs in roots and leaves of wheat seedlings were induced by salt stress. DEGs were predominantly enriched in cellular amino acid catabolic process, response to external biotic stimulus, regulation of the response to salt stress, reactive oxygen species (ROS) biosynthetic process, regulation of response to osmotic stress, ect. The DEMs were mostly associated with amino acid metabolism, carbohydrate metabolism, phenylalanine metabolism, carbapenem biosynthesis, and pantothenate and CoA biosynthesis. Further analysis identified some critical genes (gene involved in the oxidative stress response, gene encoding transcription factor (TF) and gene involved in the synthesis of metabolite such as alanine, asparagine, aspartate, glutamate, glutamine, 4-aminobutyric acid, abscisic acid, jasmonic acid, ect.) that potentially participated in a complex regulatory network in the wheat response to NaCl stress. The expression of the upregulated DEGs and DEMs were higher, and the expression of the down-regulated DEGs and DEMs was lower in 3-MA-treated plants under NaCl treatment. CONCLUSION: 3-MA enhanced the salt stress sensitivity of wheat seedlings by inhibiting the activity of the roots and leaves, inhibiting autophagy in the roots and leaves, increasing the content of both H2O2 and O2•-, damaged photosynthesis apparatus and changing the transcriptome and metabolome of salt-stressed wheat seedlings.

Phosphate (Pi) Starvation Up-Regulated GmCSN5A/B Participates in Anthocyanin Synthesis in Soybean (Glycine max) Dependent on Pi Availability.

Phosphorus (P) is an essential macronutrient for plant growth and development. Among adaptive strategies of plants to P deficiency, increased anthocyanin accumulation is widely observed in plants, which is tightly regulated by a set of genes at transcription levels. However, it remains unclear whether other key regulators might control anthocyanin synthesis through protein modification under P-deficient conditions. In the study, phosphate (Pi) starvation led to anthocyanin accumulations in soybean (Glycine max) leaves, accompanied with increased transcripts of a group of genes involved in anthocyanin synthesis. Meanwhile, transcripts of GmCSN5A/B, two members of the COP9 signalosome subunit 5 (CSN5) family, were up-regulated in both young and old soybean leaves by Pi starvation. Furthermore, overexpressing GmCSN5A and GmCSN5B in Arabidopsis thaliana significantly resulted in anthocyanin accumulations in shoots, accompanied with increased transcripts of gene functions in anthocyanin synthesis including AtPAL, AtCHS, AtF3H, AtF3'H, AtDFR, AtANS, and AtUF3GT only under P-deficient conditions. Taken together, these results strongly suggest that P deficiency leads to increased anthocyanin synthesis through enhancing expression levels of genes involved in anthocyanin synthesis, which could be regulated by GmCSN5A and GmCSN5B.

Persistence and metabolism of the diamide insecticide cyantraniliprole in tomato plants.

Plant uptake and metabolism of pesticides are complex and dynamic processes, which contribute to the overall toxicity of the pesticides. We investigated the metabolic fate of cyantraniliprole, a new diamide class of insecticide, during various growth stages of tomato. Cyantraniliprole was the major residue in leaves, flowers, and fruits, with the relative metabolite-to-parent ratios maintained at < 10% up to 28 days after treatment (DAT). Mature leaves contained consistently higher residues of cyantraniliprole than young leaves throughout the study. Flowers contained the highest cyantraniliprole residues up to 21 DAT, then gradually decreased. Immature green fruits had the highest cyantraniliprole residues (5.3 ± 0.7 ng/g; 42 DAT), and decreased toward red ripening stages (1.4 ± 0.2 ng/g; 84 DAT). Metabolism of cyantraniliprole primarily occurred in the foliage, where 21 metabolites were tentatively identified. Flowers and fruits contained 14 and four of these metabolites, respectively. Major transformation pathways were characterized by ring closure, followed by N-demethylation, and glycosylation. Additionally, plant metabolism of cyantraniliprole was also associated with several minor phase-I, phase-II, and breakdown metabolites. The occurrence of these metabolites in plants varied as a function of tissue types and their developmental stages. Our study highlights a tissue-specific biotransformation and accumulation of metabolites of cyantraniliprole in tomato.