Effect of Sulfated Chitooligosaccharides on Wheat Seedlings (Triticum aestivum L.) under Salt Stress

Preparation of Chitooligosaccharides with Specific Sequence Arrangement and Their Effect on Inducing Salt Resistance in Wheat Seedlings

Chitooligosaccharides (COS) exhibits good activity of inducing plant resistance, but the structure-activity relationship is still unclear. In this study, chitin oligosaccharides (CHOS) with a degree of polymerization (DP) of 2~6 were used as raw materials. Three deacetylases (NodB, VcCOD, and ArCE4A) were employed to prepare three different sequence-arranged COSs, namely N-COS, C-COS, and A-COS, and their structures were characterized by infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry. Further studies were conducted on inducing the plant salt resistance of the three different sequence-arranged COSs on wheat seedlings. The results showed a sequence-dependent effect of COS inducing plant salt resistance. Among them, A-COS exhibited the best activity. When sprayed at a concentration of 10 mg/L on wheat seedlings under salt stress for 3 days, the leaf length of the wheat seedlings sprayed with A-COS was recovered, and the wet mass and dry mass were recovered by 20.40% and 6.64%, respectively. Following the enhancement of proline accumulation, the malondialdehyde content decreased by 34.75%, and the Na+/K+ ratio also exhibited a significant reduction, thereby alleviating salt stress-induced damage. This study was the first to demonstrate the effect of COS with specific sequences on inducing plant salt resistance, providing a theoretical basis for the development of a new generation of efficient COS plant biostimulator.

Ancient Hulled Wheat: An Antioxidant-Rich Crop for Boron-Contaminated Soils

This study investigated the boron (B) tolerance of four ancient hulled wheat species, examining their morphological, physiological, and antioxidant responses to varying B concentrations and the mitigating effects of exogenous glycine betaine (GB). Results revealed that B initially promoted root and shoot biomass, but higher concentrations induced growth inhibition, mitigated by GB application. B exposure increased total protein content and antioxidant enzyme activities at lower concentrations but decreased them at higher concentrations, indicating oxidative stress. Exogenous GB enhanced antioxidant enzyme activities and proline accumulation, alleviating oxidative damage. These findings suggest varying B tolerance among ancient hulled wheat varieties. GB effectively mitigated B-induced stress by bolstering antioxidant defenses and promoting osmotic adjustment. This highlights the potential of ancient hulled wheat as a genetic resource for developing B-tolerant wheat cultivars.

Chitosan-oligosaccharide alleviates chlorpyrifos-induced biochemical and developmental toxicity and reduces its accumulation in wheat (Triticum aestivum L.)

Chlorpyrifos (CHP) contamination affects agricultural land and poses significant risks to plants and humans. Chitosan-oligosaccharide (COS) enhances plant resilience under stress and boosts the activity of enzymes metabolizing exogenous substances. This study aimed to explore the potential and mechanism of COS in mitigating CHP phytotoxicity and reducing CHP accumulation through both pot and field experiments. The results indicated that CHP exposure caused oxidative stress and decreased photosynthesis by 18.5 % in wheat. COS up-regulated the expression of antioxidant enzyme genes in CHP-stressed plants, resulting in a 12.1 %-29.4 % increase in antioxidant enzyme activity, which resulted in an 11.3 %-12.8 % reduction in reactive oxygen species (ROS) and an 11.5 %-14.7 % reduction in malondialdehyde (MDA) content in leaves and roots, respectively. Additionally, COS increased chlorophyll content by 6.6 % by regulating genes related to chlorophyll metabolism, enhancing photosynthesis by 13.6 %. COS also reduced CHP uptake and accelerated its metabolism by upregulating CYP450, GST, and lignin biosynthesis-related genes. Wheat treated with COS exhibited a 26.7 %-28.7 % reduction in grains' CHP content, resulting in a lower health risk index (HRI). These findings provide novel insights into the potential of COS in alleviating CHP phytotoxicity and reducing its accumulation.

Soil Salinization and Ancient Hulled Wheat: A Study on Antioxidant Defense Mechanisms

Soil salinization, which is second only to soil erosion in terms of soil degradation, significantly hinders crop growth and development, leading to reduced yields. This study investigated the enzymatic and non-enzymatic antioxidant defense mechanisms of four ancient hulled wheat species under salt stress, with and without exogenous glycine betaine (0.5 mM). We aimed to assess the salt tolerance of these species and their potential for cultivation in saline/sodic soils. Our findings indicate that sodium and potassium chloride concentrations exceeding 100 mM induce significant stress in hulled wheat. However, combined salt stress (sodium and potassium chloride) reduced this stress by approximately 20-30%. Furthermore, exogenous glycine betaine supplementation almost completely alleviated the negative effects of salt stress, particularly in Triticum boeoticum. This species exhibited a remarkable ability to restore normal growth functions under these conditions. Our results suggest that ancient hulled wheat, especially T. boeoticum, may be a promising candidate for cultivation in sodium-saline soils. By supplementing with potassium fertilizers in addition to nitrogen, plants can effectively control salt influx into their cells and maintain intracellular K+/Na+ balance, thereby mitigating the adverse effects of salinity stress. This approach has the potential to increase crop yields and enhance food security in saline environments.

The preparation, modification and hepatoprotective activity of chitooligosaccharides: A review

Chitooligosaccharides (COS) has attracted increasing attention due to the various promising bioactivities, tremendous potential in agricultural, environmental nutritional and functional food fields. COS as the major degradation product from chitosan or chitin is prepared via enzymatic, chemical and physical methods. Further obtained COS generally possesses different structural characteristics, such as molecular weight, degree of acetylation and degree of polymerization. Innovations into COS modification has also broadened application of COS in nutrition as well as in agricultural safety. Due to the affinity between structure and bioactivity, diversity of structural characteristics endows COS with various bioactivities like antitumor, antioxidant and anti-inflammatory effects, especially hepatoprotective activity. Therefore, the present review narrates the recent developments in COS physicochemical properties, while paying considerable attention to preparation strategies of COS and their advantages and disadvantages. Moreover, the modification of COS is also discussed including alkylation, quaternization and sulfation, herein the structure-activity relationship of COS was highlighted. Additionally, we summarize the latest research on hepatoprotective activity and mechanisms of COS. Eventually, the future directions of research on COS were discussed, which would provide a new appreciation for the future use of COS.

Advances in the preparation, characterization, and biological functions of chitosan oligosaccharide derivatives: A review

Chitosan oligosaccharide (COS), which represent the positively charged basic amino oligosaccharide in nature, is the deacetylated and degraded products of chitin. COS has become the focus of intensive scientific investigation, with a growing body of practical and clinical studies highlighting its remarkable health-enhancing benefits. These effects encompass a wide range of properties, including antibacterial, antioxidant, anti-inflammatory, and anti-tumor activities. With the rapid advancements in chemical modification technology for oligosaccharides, many COS derivatives have been synthesized and investigated. These newly developed derivatives possess more stable chemical structures, improved biological activities, and find applications across a broader spectrum of fields. Given the recent interest in the chemical modification of COS, this comprehensive review seeks to consolidate knowledge regarding the preparation methods for COS derivatives, alongside discussions on their structural characterization. Additionally, various biological activities of COS derivatives have been discussed in detail. Lastly, the potential applications of COS derivatives in biomedicine have been reviewed and presented.

Co-application of chitooligosaccharides and arbuscular mycorrhiza fungi reduced greenhouse gas fluxes in saline soil by improving the rhizosphere microecology of soybean

Soil salinization can affect the ecological environment of soil and alter greenhouse gas (GHG) emissions. Chitooligosaccharides and Arbuscular mycorrhizal fungi (AMF) reduced the GHG fluxes of salinized soil, and this reduction was attributed to an alteration in the rhizosphere microecology, including changes in the activities of β-glucosidase, acid phosphatase, N-acetyl-β-D-glucosidase, and Leucine aminopeptidase. Additionally, certain bacteria species such as paracoccus, ensifer, microvirga, and paracyclodium were highly correlated with GHG emissions. Another interesting finding is that foliar spraying of chitooligosaccharides could transport to the soybean root system, and improve soybean tolerance to salt stress. This is achieved by enhancing the activities of antioxidant enzymes, and the changes in amino acid metabolism, lipid metabolism, and membrane transport. Importantly, the Co-application of chitooligosaccharides and Arbuscular mycorrhiza fungi was found to have a greater effect compared to their application alone.

Physcion and chitosan-Oligosaccharide (COS) synergistically improve the yield by enhancing photosynthetic efficiency and resilience in wheat (Triticum aestivum L.)

As progressively increasing food safety concerns, diversified plant diseases and abiotic stresses, environmental-friendly bio-pesticides and bio-stimulants combinations may are likely to serve as a vital means of safeguarding green and sustainable food production. Accordingly, in this study, pot and field trials were performed to examine the application potential of the combination of physcion and chitosan-Oligosaccharide (COS) in wheat production. Wheat seeds were coated with physcion and COS and the effects exerted by them on morphology, physiology and yield of the wheat were investigated. As indicated by the results, the combination of physcion and COS not only did not inhibit the growth of wheat seedlings, but also synergistically increased root vigor and photosynthetic pigment content. Simultaneously, the lignin content in the roots and leaves was increased significantly. Moreover, the result confirmed that the combination of both substances reduced the MDA content, which was correlated with the up-regulation of the transcript expression level of antioxidant enzyme genes and the resulting increased enzyme activity. Furthermore, this combination synergistically increased the net photosynthetic rate (Pn) of the flag leaves and ultimately contributed to the increase in yield. Notably, the above-mentioned desirable cooperative effect was not limited by cultivars and cultivation methods. The conclusion of this study suggested that the combination of physcion and COS synergistically improved the photosynthetic rate and resilience in wheat, such that high wheat yields can be more significantly maintained, and future food security can be more effectively ensured.

Chitooligosaccharide-induced plant stress resistance

In nature, the production of plant stress resistance traits is often induced by extreme environmental conditions. Under extreme conditions, plants can be irreversibly damaged. Intervention with phytostimulants, however, can improve plant stress resistance without causing damage to the plants themselves, hence maintaining the production. For example, exogenous substances such as proteins and polysaccharides can be used effectively as phytostimulants. Chitooligosaccharide, a plant stimulant, can promote seed germination and plant growth and development, and improve plant photosynthesis. In this review, we summarize progress in the research of chitooligosaccharide-induced plant stress resistance. The mechanism and related experiments of chitooligosaccharide-induced resistance to pathogen, drought, low-temperature, saline-alkali, and other stresses are classified and discussed. In addition, we put forward the challenges confronted by chitooligosaccharide-induced plant stress resistance and the future research concept that requires multidisciplinary cooperation, which could provide data for the in-depth study of the effect of chitooligosaccharide on plants.

Chitinase-Assisted Bioconversion of Chitinous Waste for Development of Value-Added Chito-Oligosaccharides Products

Chito-oligosaccharides (COSs) are the partially hydrolyzed products of chitin, which is abundant in the shells of crustaceans, the cuticles of insects, and the cell walls of fungi. These oligosaccharides have received immense interest in the last few decades due to their highly promising bioactivities, such as their anti-microbial, anti-tumor, and anti-inflammatory properties. Regarding environmental concerns, COSs are obtained by enzymatic hydrolysis by chitinase under milder conditions compared to the typical chemical degradation. This review provides updated information about research on new chitinase derived from various sources, including bacteria, fungi, plants, and animals, employed for the efficient production of COSs. The route to industrialization of these chitinases and COS products is also described.

Validation of a QTL on Chromosome 1DS Showing a Major Effect on Salt Tolerance in Winter Wheat

Salt stress is one the most destructive abiotic stressors, causing yield losses in wheat worldwide. A prerequisite for improving salt tolerance is the identification of traits for screening genotypes and uncovering causative genes. Two populations of F3 lines developed from crosses between sensitive and tolerant parents were tested for salt tolerance at the seedling stage. Based on their response, the offspring were classified as salt sensitive and tolerant. Under saline conditions, tolerant genotypes showed lower Na+ and proline content but higher K+, higher chlorophyll content, higher K+/Na+ ratio, higher PSII activity levels, and higher photochemical efficiency, and were selected for further molecular analysis. Five stress responsive QTL identified in a previous study were validated in the populations. A QTL on the short arm of chromosome 1D showed large allelic effects in several salt tolerant related traits. An expression analysis of associated candidate genes showed that TraesCS1D02G052200 and TraesCS5B02G368800 had the highest expression in most tissues. Furthermore, qRT-PCR expression analysis revealed that ZIP-7 had higher differential expressions under saline conditions compared to KefC, AtABC8 and 6-SFT. This study provides information on the genetic and molecular basis of salt tolerance that could be useful in development of salt-tolerant wheat varieties.

Role of melatonin in promoting plant growth by regulating carbon assimilation and ATP accumulation

Melatonin (MT) is a phytohormone important in mediating diverse plant growth processes. In this study, we performed transcriptomic, qRT-PCR, physiological and biochemical analyses of Brassica rapa seedlings in order to understand how MT promotes plant growth. The results showed that exogenous MT increased the rate of cyclic electron flow around photosystem (PS) I, fluorescence quantum yield, and electron transport efficiency between PSII and PSI to promote the vegetative growth of B. rapa seedlings without affecting oxidative stress level, as compared to control. However, MT treatment significantly reduced photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) by 2.25-, 1.23- and 3.50-fold at 0.05 level, respectively. This occurred in parallel with the down-regulation of the genes for carbon fixation in photosynthetic organisms in a KEGG pathway enrichment. More accelerated plant growth despite the reduced photosynthesis rate and the enhanced electron transport rate suggested that NADPH and adenosine triphosphate (ATP) were preferentially diverted into other anabolic reactions than the Calvin cycle upon MT application. MT treatment increased ATP level and facilitated carbon assimilation into primary metabolism that led to a significant enhancement of soluble protein, sucrose, and fructose, but a significant decrease in glucose content. MT-induced carbon assimilation into primary metabolism was driven by up-regulation of the genes for glutathione metabolism, Krebs cycle, ribosome, and DNA replication in a KEGG pathway enrichment, as well as down-regulation of the genes for secondary metabolites. Our results provide an insight into MT-mediated metabolic adjustments triggered by coordinate changes in a wide range of gene expression profiles to help improve the plant functionality.

Synthesis of γ-Aminobutyric Acid-Modified Chitooligosaccharide Derivative and Enhancing Salt Resistance of Wheat Seedlings

Salinity is one of the major abiotic stresses limiting crop growth and productivity worldwide. Salt stress during germination degenerates crop establishment and declines yield in wheat, therefore alleviating the damage of salt stress to wheat seedlings is crucial. Chitooligosaccharide (COS) was grafted with γ-aminobutyric acid based on the idea of bioactive molecular splicing, and the differences in salt resistance before and after grafting were compared. The expected derivative was successfully synthesized and exhibited better salt resistance-inducing activity than the raw materials. By activating antioxidant enzymes such as superoxide dismutases (SOD), catalase (CAT) and phenylalanine ammonia-lyase (PAL) and subsequently eliminating reactive oxygen species (ROS) in a timely manner, the rate of O⁻₂ production and H₂O₂ content of wheat seedlings were reduced, and the dynamic balance of free radical metabolism in the plant body was maintained. A significantly reduced MDA content, reduced relative permeability of the cell membrane, and decreased degree of damage to the cell membrane were observed. A significant increase in the content of soluble sugar, maintenance of osmotic regulation and the stability of the cell membrane structure, effective reduction in the salt stress-induced damage to wheat, and the induction of wheat seedling growth were also observed, thereby improving the salt tolerance of wheat seedlings.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

Chitosan oligosaccharide alleviates the growth inhibition caused by physcion and synergistically enhances resilience in maize seedlings

The use of biopesticides has gradually become essential to ensure food security and sustainable agricultural production. Nevertheless, the use of single biopesticides is frequently suboptimal in agricultural production given the diversity of biotic and abiotic stresses. The present study investigated the effects of two biopesticides, physcion and chitosan-oligosaccharide (COS), alone and in combination, on growth regulation and antioxidant potential of maize seedlings by seed coating. As suggested from the results, physcion significantly inhibited the growth of the shoots of maize seedlings due to the elevated respiration rate. However, COS significantly reduced the growth inhibition induced by physcion in maize seedlings by lowering the respiration rate and increasing the content of photosynthetic pigments and root vigor, which accounted for lower consumption of photosynthesis products, a higher photosynthetic rate and a greater nutrient absorption rate. Thus, an improved growth was identified. As indicated from the in-depth research, the application of physcion and COS combination is more effective in down-regulated the malondialdehyde (MDA) content by facilitating the activities of the antioxidative enzymes (i.e., superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (G-POD)). Such results indicated that the combined use of physcion and COS neither affected the normal growth of maize seedlings, but also synergistically improved the antioxidant potential of the maize plants, resulting in plants with high stress resistance. Thus, the combined use of physcion and COS by seed coating in maize production has great potential to ensure yield and sustainable production of maize.

Metabonomics analysis of drought resistance of wheat seedlings induced by β-aminobutyric acid-modified chitooligosaccharide derivative

Chitooligosaccharide grafted with β-aminobutyric acid based on the idea of bioactive molecular splicing was prepared, and the differences in drought resistance activity before and after grafting were compared. The mechanism was investigated by comparing the differences of the derivative with the Control and Drought about metabolomes. The results showed that the expected derivative was successfully synthesized, named COS-BABA, and had better drought resistance-inducing activity than the raw materials. We suggest that COS-BABA induced drought resistance through second messenger-induced activation of signaling pathways related to traumatic acid and indol-3-lactic acid, which enhanced nucleic acid metabolism to accumulate nucleotides and decreased some amino acids to facilitate protein synthesis. These proteins are regulated to strengthen photosynthesis, resulting in the promotion of carbohydrate metabolism. The accumulation of unsaturated fatty acids stabilized the cell membrane structure and prevented nonstomatal water dissipation. This study provides ideas for the development of more effective drought resistance inducers.

Microbial chitinases: properties, enhancement and potential applications

Chitinases are a category of hydrolytic enzymes that catalyze chitin and are formed by a wide variety of microorganisms. In nature, microbial chitinases are primarily responsible for chitin decomposition and play a vital role in the balance of carbon and nitrogen ratio in the ecosystem. The physicochemical attributes and the source of chitinase are the main bases that determine their functional characteristics and hydrolyzed products. Several chitinases have been reported and characterized, and they obtain a wider consideration for their utilization in a large number of uses such as in agriculture, food, environment, medicine and pharmaceutical companies. The antifungal and insecticidal impacts of several chitinases have been extensively studied, aiming to protect crops from phytopathogenic fungi and insects. Chitooligosaccharides synthesized by chitin degradation have been shown to improve human health through their antimicrobial, antioxidant, anti-inflammatory and antitumor properties. This review aims at investigating chitinase production, properties and their potential applications in various biotechnological fields.

The Potential of Using Chitosan on Cereal Crops in the Face of Climate Change

This review presents the main findings from measurements carried out on cereals using chitosan, its derivatives, and nanoparticles. Research into the use of chitosan in agriculture is growing in popularity. Since 2000, 188 original scientific articles indexed in Web of Science, Scopus, and Google Scholar databases have been published on this topic. These have focused mainly on wheat (34.3%), maize (26.3%), and rice (24.2%). It was shown that research on other cereals such as millets and sorghum is scarce and should be expanded to better understand the impact of chitosan use. This review demonstrates that this chitosan is highly effective against the most dangerous diseases and pathogens for cereals. Furthermore, it also contributes to improving yield and chlorophyll content, as well as some plant growth parameters. Additionally, it induces excellent resistance to drought, salt, and low temperature stress and reduces their negative impact on cereals. However, further studies are needed to demonstrate the full field efficacy of chitosan.

Melatonin elevated Sclerotinia sclerotiorum resistance via modulation of ATP and glucosinolate biosynthesis in Brassica rapa ssp. pekinensis

Sclerotinia stem rot is a common disease found in Brassica rapa that is caused by the necrotic plant pathogen Sclerotinia sclerotiorum. Melatonin (MT) has known biological activity and effectively relieved this type of Sclerotinia stem rot in B. rapa. To better understand the mechanisms behind MT-induced S. sclerotiorum resistance in B. rapa, we performed both proteomic and metabolomic analysis. Our results showed that during S. sclerotiorum infection, thiamine synthesis was activated and defended against it. In infected leaves, ribosomal synthesis-related proteins responded positively to MT treatment. Integrated proteomic and metabolomic analysis showed that amino acid metabolism was activated by MT treatment. After MT treatment, adenosine-triphosphate (ATP) content and the activity of antioxidant enzymes were both increased in B. rapa infected leaves. Cysteine synthase, sulfur transfer-related proteins, and glucosinolate (GS) were all increased after MT treatment in infected B. rapa leaves. Taken together, these results indicated that B. rapa leaves promoted thiamine formation to defend against S. sclerotiorum infection. Moreover, MT helped further induce antioxidant activation in B. rapa in an ATP-dependent manner and stimulating GS biosynthesis to well inhibit the S. sclerotiorum infection. SIGNIFICANCE: Melatonin (MT) has biological activity and effectively relieved the Sclerotinia stem rot of Brassica rapa caused by the necrotic plant pathogen Sclerotinia sclerotiorum. In order to reveal the molecular mechanisms of MT-induced S. sclerotiorum resistance in B. rapa, comprehensive proteomic and metabolomic analyses were conducted. The integration analysis of omic-data illustrated that the modulation of ATP and glucosinolate biosynthesis induced by MT administration helped to defend the infection of S. sclerotiorum in B. rapa. Our results will provide insights into MT-induced anti-fungal mechanism and therapeutic strategies to mitigate Sclerotinia stem rot of B. rapa, thereby increasing plant yield and decreasing economic losses.

Effects of low molecular weight polysaccharides from Ulva prolifera on the tolerance of Triticum aestivum to osmotic stress

Polysaccharides derived from seaweeds can be used as biostimulants to enhance plant resistance to different stressors. In this study, we investigated the effects of applying low molecular weight polysaccharides (LPU) derived from Ulva prolifera with 14.2 kDa on the responses of wheat (Triticum aestivum) to osmotic stress. The results showed that osmotic stress simulated using polyethylene glycol inhibited seedling growth, whereas we observed increases in the fresh weights and shoot lengths of seedlings treated with polysaccharide for 120 h. Furthermore, we observed enhanced activities of antioxidant enzymes, and significant reductions in malondialdehyde content of 23.13%, 19.82%, and 20.04% in response treatment for 120 h with 0.01%, 0.03%, and 0.05% LPU, respectively, relative to those in the group treated with polyethylene glycol alone. In all treatments, expression of the P5CS gene was upregulated to promote proline accumulation. Moreover, after 120 h, exogenously applied LPU induced the expression of stress-related genes, including SnRK2, Wabi5, Wrab18, and Wdhn13. Collectively, these findings indicate that LPU might have the effect of regulating the abscisic acid-dependent pathway in wheat, thereby increasing seedling antioxidant capacity and growth. Application of LPU may accordingly represent an effective approach for enhancing the resistance to osmotic stress in wheat.

Synthesis and effects of the selective oxidation of chitosan in induced disease resistance against Botrytis cinerea

Plant fungal diseases can lead to yield reduction and quality degradation in crops, which usually cause serious economic losses. Additionally, chemical fungicides used in the prevention and control of plant diseases are increasingly restricted due to resistance development and high toxicity. Therefore, biogenic fungicides such as chitosan with low toxicity and good biocompatibility are receiving increasing attention. This study found that the acid swelling chitosan pretreatment method can accelerate the rate of the specific oxidation of chitosan catalyzed by the TEMPO-NaBr-NaOCl system. This study proved that OCTS induces plant disease resistance, and the control efficiencies achieved in protection and treatment experiments against Botrytis cinerea were 80.6 % and 83.4 %, respectively, at 400 μg/mL OCTS. In addition, OCTS can promote plant growth and enhance plant defense enzyme activities. This research has realized a forward-looking exploration of the application of OCTS in the agricultural field.

Effects of chitooligosaccharides supplementation with different dosages, molecular weights and degrees of deacetylation on growth performance, innate immunity and hepatopancreas morphology in Pacific white shrimp (Litopenaeus vannamei)

Three trials were conducted to comprehensively evaluate the application of chitooligosaccharides (COSs) different dosages, molecular weights (MW) and degrees of deacetylation (DD) as a feed additive for Pacific white shrimp (Litopenaeus vannamei). In trial 1, COSs (3 KDa and 85% DD) at four different dosages (0.05%, 0.1%, 0.15% and 0.2%) were added to feed to investigate the appropriate dosages. The survival ratio (SR) of the shrimps was not significantly different (P > 0.05) between the control and treatment groups. The shrimps fed with 0.1% COSs supplementation exhibited the highest wet body weight (FBW), specific growth ratio (SGR), and weight gain (WG) and the lowest feed conversion ratio (FCR). In trial 2, COSs with different MW (85% DD and 0.1% dosage) were tested. Except for the group treated with the 12 KDa COSs, all shrimps fed with COSs had remarkably higher (P < 0.05) FBW, WG, and SGR and lower FCR (P < 0.05) than the control group, and shrimps fed with the 1 KDa COSs showed most positive effects. In trial 3, COSs with different DD (MW of 1 KDa and 0.1% dosage) were further studied. The different DD were DD5, DD25, DD50, DD75, and DD95. Shrimps fed COSs-supplemented diets of DD75 or DD95 exhibited higher (P < 0.05) FBW, WG and SGR and lower FCR than the other groups. The DD95 group had the highest FBW, WG and SGR and the lowest FCR, but there were no significant differences (P > 0.05) between the DD75 and DD95 groups. Moreover, for COSs supplementation, especially for the DD75 and DD95 groups, the antioxidant parameters were significantly different from those of the other groups. Furthermore, groups fed diets with COSs supplementation had higher (P < 0.05) trypsin activity than those fed control diets. In addition, immune and antioxidant gene expression and the morphology of the hepatopancreas were affected by the DD of COSs. Therefore, the additive dosages, molecular weights and degrees of deacetylation of COSs significantly affected the growth performance of the shrimps; therefore, it is particularly important to determine the optimum parameters of COSs.

Chitosan-PVA and Copper Nanoparticles Improve Growth and Overexpress the SOD and JA Genes in Tomato Plants under Salt Stress

Saline stress severely affects the growth and productivity of plants. The activation of hormonal signaling cascades and reactive oxygen species (ROS) in response to salt stress are important for cellular detoxification. Jasmonic acid (JA) and the enzyme SOD (superoxide dismutase), are well recognized markers of salt stress in plants. In this study, the application of chitosan-polyvinyl alcohol hydrogels (Cs-PVA) and copper nanoparticles (Cu NPs) on the growth and expression of defense genes in tomato plants under salt stress was evaluated. Our results demonstrate that Cs-PVA and Cs-PVA + Cu NPs enhance plant growth and also promote the expression of JA and SOD genes in tomato (Solanum lycopersicum L.), under salt stress. We propose that Cs-PVA and Cs-PVA + Cu NPs mitigate saline stress through the regulation of oxidative and ionic stress.

A Review of the Preparation, Analysis and Biological Functions of Chitooligosaccharide

Chitooligosaccharide (COS), which is acknowledged for possessing multiple functions, is a kind of low-molecular-weight polymer prepared by degrading chitosan via enzymatic, chemical methods, etc. COS has comprehensive applications in various fields including food, agriculture, pharmacy, clinical therapy, and environmental industries. Besides having excellent properties such as biodegradability, biocompatibility, adsorptive abilities and non-toxicity like chitin and chitosan, COS has better solubility. In addition, COS has strong biological functions including anti-inflammatory, antitumor, immunomodulatory, neuroprotective effects, etc. The present paper has summarized the preparation methods, analytical techniques and biological functions to provide an overall understanding of the application of COS.

Enhancing antioxidant systems by exogenous spermine and spermidine in wheat (Triticum aestivum) seedlings exposed to salt stress

Plants have evolved complex mechanisms to mitigate osmotic and ionic stress caused by high salinity. The effect of exogenous spermine (Spm) and spermidine (Spd) on defence responses of wheat seedlings under NaCl stress was investigated by measuring antioxidant enzyme activities and the transcript expression of corresponding genes. Exogenous Spm and Spd decreased the level of malondialdehyde, increased chlorophyll and proline contents, and modulated PSII activity in wheat seedlings under salt stress. Spermidine alleviated negative effects on CO2 assimilation induced by salt stress in addition to significantly increasing the activity and content of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). It appears Spd conferred salinity tolerance in wheat seedlings by enhancing photosynthetic capacity through regulation of gene expression and the activity of key CO2 assimilation enzymes. Exogenous Spm regulated activities of different antioxidant enzymes (catalase, glutathione reductase, dehydroascorbate reductase, ascorbate peroxidase, and superoxide dismutase) and efficiently modulate their transcription levels in wheat seedlings under salt stress. It is likely that Spm plays a key role in alleviating oxidative damage of salt stress by adjusting antioxidant enzyme activities in plants. In addition, exogenous Spd increased transcript level of spermine synthase under salt stress. Salinity stress also caused an increase in transcript levels of diamine oxidase (DAO) and polyamine oxidase (PAO). Exogenous Spd application resulted in a marked increase in free Spd and Spm contents under saline conditions. These results show that exogenous Spd and Spm effectively upregulated transcriptional levels of antioxidant enzyme genes and improved the defence response of plants under salt stress.

Molybdenum Sulfide Induce Growth Enhancement Effect of Rice ( Oryza sativa L.) through Regulating the Synthesis of Chlorophyll and the Expression of Aquaporin Gene

Molybdenum sulfide (MoS₂) has been applied widely in industrial and environmental application, leading to increasing release into environment. So far, no studies have been investigated with regard to the potential effect of MoS₂ on plants. Herein, we studied the impact of MoS₂ on the growth, chlorophyll content, lipid peroxidation, antioxidase system, and aquaporins of rice for the first time. Results showed that MoS₂ did not significantly affect the germination of rice seeds, malonaldehyde (MDA) content, and the antioxidant enzyme activity. While the length and biomass of rice root and shoot, chlorophyll content index (CCI), and expression of aquaporin genes were significantly increased. Based on these results, we concluded that MoS₂ promoted rice growth through (i) the promotion of nitrogen source assimilation, (ii) the enhancement of photosynthesis, enzymatic-related biochemical reactions, and metabolic processes, subsequently, (iii) the acceleration of cell division and expansion, furthermore (iv) no abiotic stress and favorable condition of antioxidant enzyme system. These results provided an important insight into the further application of MoS₂ on agriculture and environment.

Low-Molecular-Weightt Polysaccharides From Pyropia yezoensis Enhance Tolerance of Wheat Seedlings (Triticum aestivum L.) to Salt Stress

Soil salinity is one of the major issues worldwide that affects plant growth and reduces agricultural productivity. Seaweed polysaccharides have been shown to promote crop growth and improve the resistance of plant to abiotic stresses. Pyropia yezoensis is a commercially important edible red alga in Southeast Asia. However, there is little research on the application of polysaccharides from P. yezoensis in agriculture. The molecular weight (MW) of polysaccharides influences their properties. Therefore, in this study, four representative polysaccharides from P. yezoensis (PP) with different MWs (MW: 3.2, 10.5, 29.0, and 48.8 kDa) were prepared by microwave-assisted acid hydrolysis. The relationship between the degradation of polysaccharides from P. yezoensis (DPP) and their effects on plant salt tolerance was investigated. The results showed that exogenous PP and DPPs increased wheat seedling shoot and root lengths, and fresh and dry weights, alleviated membrane lipid peroxidation, increased the chlorophyll content and enhanced antioxidant activities. The expression level examination analysis of several Na⁺/K⁺ transporter genes suggested that DPPs could protect plants from the damage of salt stress by coordinating the efflux and compartmentation of Na⁺. The results demonstrated that polysaccharides could regulate antioxidant enzyme activities and modulate intracellular ion concentration, thereby to protect plants from salt stress damage. Furthermore, there was a significant correlation between the tolerance of wheat seedlings to salt stress and MW of polysaccharides. The results suggested that the lower-MW samples (DPP1, 3.2 kDa) most effectively protect wheat seedlings against salt stress.

Oligo-Alginate with Low Molecular Mass Improves Growth and Physiological Activity of Eucomis autumnalis under Salinity Stress

Biopolymers have become increasingly popular as biostimulators of plant growth. One of them, oligo-alginate, is a molecule that regulates plant biological processes and may be used in horticultural practice as a plant growth regulator. Biostimulators are mainly used to improve plant tolerance to abiotic stresses, including salinity. The aim of the study was to assess the effects of salinity and oligo-alginate of various molecular masses on the growth and physiological activity of Eucomis autumnalis. The species is an ornamental and medicinal plant that has been used for a long time in the traditional medicine of South Africa. The bulbs of E. autumnalis were coated using depolymerized sodium alginate of molecular mass 32,000; 42,000, and 64,000 g mol-1. All of these oligo-alginates fractions stimulated plant growth, and the effect was the strongest for the fraction of 32,000 g mol-1. This fraction was then selected for the second stage of the study, when plants were exposed to salt stress evoked by the presence of 100 mM NaCl. We found that the oligo-alginate coating mitigated the negative effects of salinity. Plants treated with the oligomer and watered with NaCl showed smaller reduction in the weight of the above-ground parts and bulbs, pigment content and antioxidant activity as compared with those not treated with the oligo-alginate. The study demonstrated for the first time that low molecular mass oligo-alginate may be used as plant biostimulator that limits negative effects of salinity in E. autumnalis.

Relationship between the Degree of Polymerization of Chitooligomers and Their Activity Affecting the Growth of Wheat Seedlings under Salt Stress

Seven chitooligomers (COSs) with determined degrees of polymerization (DPs) (chitotetraose to chitooctaose, DP 8-10, DP 10-12) and a heterogeneous COS with various DPs were first applied to explore the relationship between the DP of COSs and their effect on the growth of wheat seedlings under salt stress. The results showed that COS could promote the growth of wheat seedlings under salt stress. Moreover, chitohexaose, chitoheptaose, and chitooctaose exhibited stronger activity compared with other COS samples, which suggested that their activity had a close relationship with the DP. After 10 days of treatment with chitohexaose, chitoheptaose, and chitooctaose, the photosynthetic parameters were obviously improved. The soluble sugar and proline contents were improved by 26.7-53.3 and 43.6-70.2%, respectively, whereas the concentration of malondialdehyde (MDA) was reduced by 36.8-49.6%. In addition, the antioxidant enzyme activities were clearly activated. At the molecular level, the results revealed that they could obviously induce the expression of Na⁺/H⁺ antiporter genes.