Metabolite Profiling of Wheat Seedlings Induced by Chitosan: Revelation of the Enhanced Carbon and Nitrogen Metabolism

Chitosan-strigolactone mimics with synergistic effect: A new concept for plant biostimulants

The paper reports new multifunctional plant biostimulant formulations obtained via in situ hydrogelation of chitosan with salicylaldehyde in the presence of a mimetic naphthalimide-based strigolactone, in specific conditions. Various analytical techniques (FTIR, 1H NMR, SEM, POM, TGA, WRXD) were employed to understand the particularities of the hydrogelation mechanism and its consequences on the formulations' properties. Further, in order to evaluate their potential for the targeted application, the swelling in media of pH characteristic for different soils, water holding capacity, soil biodegradability, in vitro release of the strigolactone mimic and impact on tomatoes plant growth in laboratory conditions were investigated and discussed. It was found that the strigolactone mimic has the ability to bond to the chitosan matrix via physical forces, favoring a prolonged release. Moreover, the combination of chitosan with the strigolactone mimic in an optimal mass ratio triggered a synergistic effect on the plant growth, up to 4 times higher compared to the neat control soil.

Chitosan microparticles mitigate nitrogen deficiency in tomato plants

Nitrogen (N) deficiency is one of the most prevalent nutrient deficiencies in plants, and has a significant impact on crop yields. In this work we aimed to develop and evaluate innovative strategies to mitigate N deficiency. We studied the effect of supplementing tomato plants grown under suboptimal N nutrition with chitosan microparticles (CS-MPs) during short- and long-term periods. We observed that the supplementation with CS-MPs prevented the reduction of aerial biomass and the elongation of lateral roots (LR) triggered by N deficiency in tomato plantlets. In addition, levels of nitrates, amino acids and chlorophyll, which decreased drastically upon N deficiency, were either partial or totally restored upon CS-MPs addition to N deficient media. Finally, we showed that CS-MPs treatments increased nitric oxide (NO) levels in root tips and caused the up-regulation of genes involved in N metabolism. Altogether, we suggest that CS-MPs enhance the growth and development of tomato plants under N deficiency through the induction of biochemical and transcriptional responses that lead to increased N metabolism. We propose treatments with CS-MPs as an efficient practice focused to mitigate the nutritional deficiencies in N impoverished soils.

Alginate-Chitosan Biodegradable and Biocompatible Based Hydrogel for Breast Cancer Immunotherapy and Diagnosis: A Comprehensive Review

Breast cancer is the most common type of cancer and the second leading cause of cancer-related mortality in females. There are many side effects due to chemotherapy and traditional surgery, like fatigue, loss of appetite, skin irritation, and drug resistance to cancer cells. Immunotherapy has become a hopeful approach toward cancer treatment, generating long-lasting immune responses in malignant tumor patients. Recently, hydrogel has received more attention toward cancer therapy due to its specific characteristics, such as decreased toxicity, fewer side effects, and better biocompatibility drug delivery to the particular tumor location. Researchers globally reported various investigations on hydrogel research for tumor diagnosis. The hydrogel-based multilayer platform with controlled nanostructure has received more attention for its antitumor effect. Chitosan and alginate play a leading role in the formation of the cross-link in a hydrogel. Also, they help in the stability of the hydrogel. This review discusses the properties, preparation, biocompatibility, and bioavailability of various research and clinical approaches of the multipolymer hydrogel made of alginate and chitosan for breast cancer treatment. With a focus on cases of breast cancer and the recovery rate, there is a need to find out the role of hydrogel in drug delivery for breast cancer treatment.

Chitosan-based materials for dental implantology: A comprehensive review

Chitosan, a versatile biopolymer, has gained recognition in the discipline of dental implantology due to possessing salient properties. This comprehensive review explores the potential of chitosan in dental implants, focusing on its biocompatibility, bioactivity, and the various chitosan-based materials that have been utilized for dental implant therapy. The review also highlights the importance of surface treatment in dental implants to enhance osseointegration and inhibit bacterial biofilm formation. Additionally, the chemical structure, properties, and sources of chitosan are described, along with its different structural forms. The characteristics of chitosan particularly color, molecular weight, viscosity, and degree of deacetylation are discussed about their influence on its applications. This review provides valuable insights into the promising utilization of polymeric chitosan in enhancing the success and functionality of dental implants. This study highlights the potential applications of chitosan in oral implantology. Chitosan possesses various advantageous properties, including muco-adhesiveness, hemostatic action, biocompatibility, biodegradability, bioactivity, and antibacterial and antifungal activities, which enhance its uses in dental implantology. However, it has limited aqueous solubility at the physiological pH, which sometimes restricts its biological application, but this problem can be overcome by using modified chitosan or chitosan derivatives, which have also shown encouraging results. Recent research suggests that chitosan may act as a promising material for coating titanium-based implants, improving osteointegration together with antibacterial properties.

Curd, seed yield and disease resistance of cauliflower are enhanced by oligosaccharides

Background

Oligosaccharides have been demonstrated as promoters for enhancing plant growth across several crops by elevating their secondary metabolites. However, the exploration of employing diverse oligosaccharides for qualitative trait improvements in cauliflower largely unknown. This study was intended to uncover the unexplored potential, evaluating the stimulatory effects of three oligosaccharides on cauliflower's curd and seed production.

Methods

Two experiments were initiated in the early (15 September) and mid-season (15 October). Four treatments were implemented, encompassing a control (water) alongside chitosan oligosaccharide (COS 50 mg.L-1) with a degree of polymerization (DP) 2-10, oligo galacturonic acid (OGA 50 mg.L-1) with DP 2-10 and alginate oligosaccharide (AOS 50 mg.L-1) with DP 2-7.

Results

Oligosaccharides accelerated plant height (4-17.6%), leaf number (17-43%), curd (5-14.55%), and seed yield (17.8-64.5%) in both early and mid-season compared to control. These enhancements were even more pronounced in the mid-season (7.6-17.6%, 21.37-43%, 7.27-14.55%, 25.89-64.5%) than in the early season. Additionally, three oligosaccharides demonstrated significant disease resistance against black rot in both seasons, outperforming the control. As a surprise, the early season experienced better growth parameters than the mid-season. However, performance patterns remained more or less consistent in both seasons under the same treatments. COS and OGA promoted plant biomass and curd yield by promoting Soil Plant Analysis Development (SPAD) value and phenol content. Meanwhile, AOS increased seed yield (56.8-64.5%) and elevated levels of chlorophyll, ascorbic acid, flavonoids, while decreasing levels of hydrogen per oxide (H2O2), malondialdehyde (MDA), half maximal inhibitory concentration (IC50), and disease index. The correlation matrix and principal component analysis (PCA) supported these relations and findings. Therefore, COS and OGA could be suggested for curd production and AOS for seed production in the early season, offering resistance to both biotic and abiotic stresses for cauliflower cultivation under field conditions.

Urea Coated with Polyaspartic Acid-Chitosan Increases Foxtail Millet (Setaria italica L. Beauv.) Grain Yield by Improving Nitrogen Metabolism

Innovative measures of nitrogen (N) fertilization to increase season-long N availability is essential for gaining the optimal foxtail millet (Setaria italica L. Beauv.) productivity and N use efficiency. A split plot field experiment was conducted using the foxtail millet variety Huayougu 9 in 2020 and 2021 in Northeast China to clarify the physiological mechanism of a novel polyaspartic acid-chitosan (PAC)-coated urea on N assimilation and utilization from foxtail millet. Conventional N fertilizer (CN) and the urea-coated -PAC treatments were tested under six nitrogen fertilizer application levels of 0, 75, 112.5, 150, 225, and 337.5 kg N ha-1. The results showed that compared to CN, PN increased the foxtail millet yield by 5.53-15.75% and 10.43-16.17% in 2020 and 2021, respectively. PN increased the leaf area index and dry matter accumulation by 7.81-18.15% and 12.91-41.92%, respectively. PN also enhanced the activities of nitrate reductase, glutamine synthetase, glutamic oxaloacetic transaminase, and glutamic-pyruvic transaminase, thereby increasing the soluble protein in the leaf, plant, and grain N content at harvest compared to CN. Consequently, partial factor productivity from applied N, the agronomic efficiency of applied N, recovery efficiency of applied N, and physiological efficiency of applied N of foxtail millet under PN treatments compared to CN were increased. The improvement effect of the items above was more noticeable under the low-middle N application levels (75, 112.5, and 150 kg N ha-1). In conclusion, the PAC could achieve the goal of high yield and high N use efficiency in foxtail millet under the background of a one-time basic fertilizer application.

Source-sink coordinated peanut cultivar increases yield and kernel protein content through enhancing photosynthetic characteristics and regulating carbon and nitrogen metabolisms

The grain yield of crops is determined by the synergistic interaction between source activity and sink capacity. However, source-sink interactions are far from being fully understood of peanut. Therefore, a 2-year field study (2018-2019) was conducted to compare differences in photosynthetic characteristics, carbon and nitrogen metabolism, and yield and quality of different source-sink peanut varieties. Four representative source-sink types were examined: JH5 (source-sink coordination type), SH9 (sufficient source-large sink type), ZH24 (sufficient source-few sink type), and HY36 (large source-few sink type). The results showed that the photosynthetic potential of HY36 was higher than that of the other varieties after flowering because of a large source (leaves), whereas the chlorophyll content and net photosynthetic rate of HY36 were significantly lower than those of JH5 and ZH24. Proportions of dry matter transferred to pods were significantly different among four source-sink peanut varieties. From 50 days after flowering, the dry matter distribution ratio of pods exceeded that of stems and leaves in JH5, significantly earlier than other varieties, which prolong the duration of pod-filling period, followed by SH9 and ZH24. The activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase, and glutamate synthase in JH5 were the highest among the varieties, and thus, the highest protein content was also in JH5. The activities of sucrose synthase and sucrose phosphate synthase in ZH24 were significantly higher than those in HY36. The highest oil content was also in ZH24. Among pod sink characteristics and yield, SH9 had the longest flowering period and the highest gynophore formation rate but the lowest pod-bearing rate, and the effective proportion and pod fullness were also lower than those of other varieties. The highest pod rate was in ZH24. The effective proportion and pod fullness of JH5 were higher than those of the other varieties, and its yield was also the highest, followed by SH9 and ZH24, with the lowest yield in HY36. The obtained results indicate that the source-sink coordinated variety had high Pn and chlorophyll content in the late growth stage, a long functional period of leaves, and a high proportion of assimilates transported to pods, thus promoting effective proportions and pod fullness to improve peanut yield and protein content, suggesting that different cultivation and management measures should select for different peanut varieties to best coordinate the relationship between the source and sink.

Chitosan nanoparticles upregulate C and N metabolism in soybean plants grown under elevated levels of atmospheric carbon dioxide

Despite the wide utilization of chitosan nanoparticles (CSNPs) as a promising approach for sustainable agriculture, their efficiency under elevated CO2 (eCO2), has not been evaluated. The interactive effects of CSNPs and eCO2 were evaluated on the growth and C and N metabolism of soybean plants. Plants were treated with CSNPs and grown under ambient CO2 (410 ppm, aCO2) or eCO2 (645 ppm). Regardless of CO2 level, CSNPs improved the net photosynthetic rate. CSNPs aggravated the effect of eCO2 treatment on the levels of non-structural carbohydrates (i.e., glucose, fructose, sucrose, and starch), especially in shoots, which was inconsistence with the upregulation of carbohydrates metabolizing enzymes. Being the most pivotal energetic and signaling organic compounds in higher plants, the synergistic action of CSNPs and eCO2 on the accumulation of soluble sugars upregulated the N metabolism as indicated by induced activities of nitrate reductase, arginase, glutamate dehydrogenase, glutamine synthetase, and glutamine oxoglutarate aminotransferase which was manifested finally as increased shoot and root total nitrogen content as well as proline and aspartate in roots. At the hormonal level, the coexistence of eCO2 with CSNPs further supports their positive impact on the contents of IAA and, to a lesser extent, GAs. The present data prove that the biofertilization capacity of CSNPs is even more potent under futuristic eCO2 levels and could even further improve the growth and resilience of plants.

Transcriptomics and metabolomics reveal the primary and secondary metabolism changes in Glycyrrhiza uralensis with different forms of nitrogen utilization

The roots and rhizomes of Glycyrrhiza uralensis Fisch. represent the oldest and most frequently used herbal medicines in Eastern and Western countries. However, the quality of cultivated G. uralensis has not been adequate to meet the market demand, thereby exerting increased pressure on wild G. uralensis populations. Nitrogen, vital for plant growth, potentially influences the bioactive constituents of plants. Yet, more information is needed regarding the effect of different forms of nitrogen on G. uralensis. G. uralensis seedlings were exposed to a modified Hoagland nutrient solution (HNS), varying concentrations of nitrate (KNO3), or ammonium (NH4)2SO4. We subsequently obtained the roots of G. uralensis for physiology, transcriptomics, and metabolomics analyses. Our results indicated that medium-level ammonium nitrogen was more effective in promoting G. uralensis growth compared to nitrate nitrogen. However, low-level nitrate nitrogen distinctly accelerated the accumulation of flavonoid ingredients. Illumina sequencing of cDNA libraries prepared from four groups-treated independently with low/medium NH4 + or NO3 - identified 364, 96, 103, and 64 differentially expressed genes (DEGs) in each group. Our investigation revealed a general molecular and physiological metabolism stimulation under exclusive NH4 + or NO3 - conditions. This included nitrogen absorption and assimilation, glycolysis, Tricarboxylic acid (TCA) cycle, flavonoid, and triterpenoid metabolism. By creating and combining putative biosynthesis networks of nitrogen metabolism, flavonoids, and triterpenoids with related structural DEGs, we observed a positive correlation between the expression trend of DEGs and flavonoid accumulation. Notably, treatments with low-level NH4 + or medium-level NO3 - positively improved primary metabolism, including amino acids, TCA cycle, and glycolysis metabolism. Meanwhile, low-level NH4 + and NO3 - treatment positively regulated secondary metabolism, especially the biosynthesis of flavonoids in G. uralensis. Our study lays the foundation for a comprehensive analysis of molecular responses to varied nitrogen forms in G. uralensis, which should help understand the relationships between responsive genes and subsequent metabolic reactions. Furthermore, our results provide new insights into the fundamental mechanisms underlying the treatment of G. uralensis and other Glycyrrhiza plants with different nitrogen forms.

Effect of Low Temperature on Insecticidal Protein Contents of Cotton (Gossypium herbaceum L.) in the Boll Shell and Its Physiological Mechanism

Low temperature is the main factor for global natural disasters affecting the growth and distribution of plants, and cotton may be affected by low temperature and cold damage at all growth stages. In addition, the insecticidal resistance of cultivars has been reported to perform poorly or unstably due to adverse environments. The present study aimed to investigate the impact of low temperature on the levels of insecticidal protein in Bacillus thuringiensis (Bt) transgenic cotton plants during the peak boll stage. To achieve this, two Bt cotton cultivars, Sikang1 (SK1) and Sikang3 (SK3), were subjected to different temperature regimes and durations. The findings of the study demonstrated that the expression of insecticidal protein in the boll shell of Bt transgenic cotton plants was significantly inhibited under low-temperature stress. Specifically, in 2020, compared to the CK (27 °C), the insecticidal protein content in the boll shell of SK3 decreased by 28.19% after a 48 h of a 16 °C temperature. These results suggest that low-temperature stress can negatively impact the expression of insecticidal protein in Bt transgenic cotton, highlighting the need for appropriate measures to minimize its adverse effects on cotton production. In addition, the threshold temperature that leads to a significant decrease in the content of insecticidal proteins symbolizes an upward trend as the duration of stress prolongs. Decreased Bt protein content at low temperatures is associated with changes in the N metabolism. The present study revealed a significant positive correlation between the levels of glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activities, as well as in the soluble protein levels in the boll shell and the content of the Bt protein. On the other hand, a significant negative correlation was observed between the levels of free amino acids, peptidase, and protease activities, as well as of Bt protein content. These findings suggest that, in Bt cotton production, it is crucial to remain vigilant of prolonged low-temperature disasters, which last for over 12 h and drop below 17-20 °C during the peak boll stage. Such conditions may reduce insecticidal resistance, leading to substantial economic losses.

Chitosan nanoparticles support the impact of arbuscular mycorrhizae fungi on growth and sugar metabolism of wheat crop

Arbuscular mycorrhizae fungi (AMF) symbiosis is an indispensable approach in sustainable agriculture. AMF-plant association is likely to be enhanced by the nanoparticle's application. Herein, the impact of chitosan nanoparticles (CSNPs) on the mycorrhizal colonization in wheat has been investigated. The provoked changes in wheat growth, physiology and metabolism were assessed. CSNPs treatment improved AMF colonization (52 %) by inducing the levels of auxins and strigolactones in roots by 32 and 21 %, respectively besides flavonoids exudation into the rhizosphere (9 %). Such supporting action of CSNPs was associated with improved plant biomass production (21 %) compared to AMF treatment. Both treatments synergistically enhanced the photochemical efficiency of photosystem II and stomatal conductance, therefore the photosynthetic rate was increased. The combined application of CSNPs and AMF enhanced accumulation of glucose, fructose, sucrose, and starch (12, 22, 31 and 13 %, respectively), as well as the activities of sucrose-p-synthase, invertases and starch synthase compared to AMF treatment. The synchronous application of CSNPs and AMF promoted the levels of polyphenols, carotenoids, and tocopherols therefore, improved antioxidant capacity (33 %), in the roots. CSNPs can be applied as an efficient biofertilization strategies to enhance plant growth and fitness, beside improvement of health promoting compounds in wheat.

Daphnia magna and Gammarus pulex, novel promising agents for biomedical and agricultural applications

Various studies have shown the importance of using different types of Zooplankton biomasses as an additional substance in the diet of fish. In addition, the drainage water of the fish cultures could be used in plant irrigation. In this study, biomasses of water flea Daphnia magna and Gammarus pulex collected and tested, for the first time, their effect against pathogenic microorganisms and on plant germination. The results showed significant antibacterial activity of D. magna and G. pulex against Staphylococcus aureus and Pseudomonas aeruginosa bacteria, as well as antifungal activity against Alternaria solani and Penicillium expansum, which gives the possibility to be used as biocontrol against these bacteria and plant pathogenic fungi. Furthermore, both animals showed positive activity in the germination rate of Vicia faba seed, reaching 83.0 ± 3.5 and 86.0 ± 3.8%, respectively. In conclusion, the biomasses of D. magna and G. pulex are promising and effective agents for their use in the medical field against some pathogenic microbes and as stimulators of plant growth.

Transcriptomic and Metabolomic Analysis Reveal Possible Molecular Mechanisms Regulating Tea Plant Growth Elicited by Chitosan Oligosaccharide

Chitosan oligosaccharide (COS) plays an important role in the growth and development of tea plants. However, responses in tea plants trigged by COS have not been thoroughly investigated. In this study, we integrated transcriptomics and metabolomics analysis to understand the mechanisms of chitosan-induced tea quality improvement and growth promotion. The combined analysis revealed an obvious link between the flourishing development of the tea plant and the presence of COS. It obviously regulated the growth and development of the tea and the metabolomic process. The chlorophyll, soluble sugar, and amino acid content in the tea leaves was increased. The phytohormones, carbohydrates, and amino acid levels were zoomed-in in both transcript and metabolomics analyses compared to the control. The expression of the genes related to phytohormones transduction, carbon fixation, and amino acid metabolism during the growth and development of tea plants were significantly upregulated. Our findings indicated that alerted transcriptomic and metabolic responses occurring with the application of COS could cause efficiency in substrates in pivotal pathways and hence, elicited plant growth.

Distinct metabolic profiling is correlated with bisexual flowers formation resulting from exogenous ethephon induction in melon (Cucumis melo L.)

Melon (Cucumis melo L.) is an agronomically important vegetable. Most cultivars of melon are andromonoecious and bisexual flowers only emerged from the leaf axil of lateral branches. However, the regulatory mechanism contributing to the occurrence of bisexual flowers were still obscure. In this study, ethephon was applied in two common cultivars of melon. In control without ethephon treatment, no bisexual flower was made in the main stem. However, 6.56 ± 1.42 and 6.63 ± 0.55 bisexual flowers were respectively induced in main stem of 'Yangjiaocui-QX' and 'Lvbao' after ethephon treatment, and induced bisexual flowers distributed in 12-20 nodes of main stem. During the formation of bisexual flowers, 41 metabolites were significantly up-regulated and 98 metabolites were significantly down-regulated. According to the KEGG enrichment analysis of 139 different metabolites, a total of 30 pathways were mapped and KEGG terms of "Phenylalanine, tyrosine and tryptophan biosynthesis", "Phenylalanine metabolism" and "Flavone and flavonol biosynthesis" were significantly enriched. In three significantly enriched KEGG terms, shikimic acid, L-tryptophan, L-phenylalanine, and kaempferol were significantly up-regulated while L-tyrosine, 4-hydroxycinnami acid and luteolin were significantly down-regulated in ET compared to CK. Different metabolites were also classified depend on major class features and 14 classes were acquired. The results of metabonomics and endogenous hormone identification indicated that ethylene could enhance the concentration of salicylic acid, methyl jasmonate, ABA and IAA. This study provided an important theoretical foundation for inducing bisexual flowers in main stem and breeding new varieties of melon in future.

Effect of Chitosan-Poly(Acrylic Acid) Complexes and Two Nutrient Solutions on the Growth and Yield of Two Habanero Pepper Cultivars

Chitosan (CS) is a natural polymer used in agriculture as a biostimulant that has been evaluated in different plant models. In this study, we evaluated the effect of the foliar application of chitosan–poly(acrylic acid) complexes (CS–PAA) and two nutrient solutions (A and B) on the parameters of growth and yield of two habanero pepper cultivars (Chichen Itza and Jaguar) in a greenhouse. Over the course of the experiment, eight foliar applications were carried out at 15-day intervals. Our results showed that foliar applications of CS–PAA complexes have a biostimulant effect on the habanero pepper crop by increasing the total dry biomass of the plant and the number of fruits of the two cultivars. Regarding nutrient solutions, the nutrient solution A increased the yield of the Chichen Itza cultivar; this effect was because it had a better balance of potassium and calcium compared to the nutrient solution B. These results provide advances on the use of CS–PAA complexes as a biostimulant and the management of nutrient solutions in the crop of habanero peppers.

The impact of chitosan on the early metabolomic response of wheat to infection by Fusarium graminearum

BACKGROUND

Chitosan has shown potential for the control of Fusarium head blight (FHB) disease caused by Fusarium graminearum. The objective of this study was to compare the effect of chitosan hydrochloride applied pre- or post-fungal inoculation on FHB and to better understand its' mode of action via an untargeted metabolomics study.

RESULTS

Chitosan inhibited fungal growth in vitro and, when sprayed on the susceptible wheat cultivar Remus 24 hours pre-inoculation with F. graminearum, it significantly reduced the number of infected spikelets at 7, 14 and 21 days post-inoculation. Chitosan pre-treatment also increased the average grain weight per head, the number of grains per head and the 1000-grain weight compared to the controls sprayed with water. No significant impact of chitosan on grain yield was observed when the plants were sprayed 24 hours post-inoculation with F. graminearum, even if it did result in a reduced number of infected spikelets at every time point. An untargeted metabolomic study using UHPLC-QTOF-MS on wheat spikes revealed that spraying the spikes with both chitosan and F. graminearum activated known FHB resistance pathways (e.g. jasmonic acid). Additionally, more metabolites were up- or down-regulated when both chitosan and F. graminearum spores were sprayed on the spikes (117), as compared with chitosan (51) or F. graminearum on their own (32). This included a terpene, a terpenoid and a liminoid previously associated with FHB resistance.

CONCLUSIONS

In this study we showed that chitosan hydrochloride inhibited the spore germination and hyphal development of F. graminearum in vitro, triggered wheat resistance against infection by F. graminearum when used as a pre-inoculant, and highlighted metabolites and pathways commonly and differentially affected by chitosan, the pathogen and both agents. This study provides insights into how chitosan might provide protection or stimulate wheat resistance to infection by F. graminearum. It also unveiled new putatively identified metabolites that had not been listed in previous FHB or chitosan-related metabolomic studies.

A Pivotal Role of Chitosan Nanoparticles in Enhancing the Essential Oil Productivity and Antioxidant Capacity in Matricaria chamomilla L

Chitosan is a biopolymer with several biological and agricultural applications. Recently, development of chitosan nanoparticles (CSNPs) adds additional value by further using it as an eco-friendly biostimulant. Therefore, the impact of CSNPs foliar application on the growth, essential oil productivity and antioxidant capacity of chamomile was investigated. Treatments comprised 0, 100, 200, 300 and 400 mg L−1 of CSNPs applied to plants as a foliar spray. CSNPs foliar application improved the growth and productivity of chamomile plants. Relative to the control, the flower yield was increased by 52.10 and 55.74% while the essential oil percentage was increased by 57.14 and 47.06% due to CSNPs at 300 mg L−1 during the two seasons of study. Moreover, CSNPs enhanced the photosynthetic pigments, total soluble sugars and N, P and K percentages. Interestingly, CSNPs increased the antioxidant capacity as measured by total phenolics and the antioxidant activity (DPPH). Collectively, it is suggested that CSNPs might be a promising eco-friendly bio-stimulant and it could be an alternative strategy to improve the productivity, quality and decrease the production cost of chamomile and possibly some other medicinal species.

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.

Exogenous Application of Chitosan Alleviate Salinity Stress in Lettuce (Lactuca sativa L.)

Soil salinity is one of the major factors that affect plant growth and decrease agricultural productivity worldwide. Chitosan (CTS) has been shown to promote plant growth and increase the abiotic stress tolerance of plants. However, it still remains unknown whether the application of exogenous CTS can mitigate the deleterious effects of salt stress on lettuce plants. Therefore, the current study investigated the effect of foliar application of exogenous CTS to lettuce plants grown under 100 mM NaCl saline conditions. The results showed that exogenous CTS increased the lettuce total leaf area, shoot fresh weight, and shoot and root dry weight, increased leaf chlorophyll a, proline, and soluble sugar contents, enhanced peroxidase and catalase activities, and alleviated membrane lipid peroxidation, in comparison with untreated plants, in response to salt stress. Furthermore, the application of exogenous CTS increased the accumulation of K+ in lettuce but showed no significant effect on the K+/Na+ ratio, as compared with that of plants treated with NaCl alone. These results suggested that exogenous CTS might mitigate the adverse effects of salt stress on plant growth and biomass by modulating the intracellular ion concentration, controlling osmotic adjustment, and increasing antioxidant enzymatic activity in lettuce leaves.

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.

Chitosan nanoparticles effectively combat salinity stress by enhancing antioxidant activity and alkaloid biosynthesis in Catharanthus roseus (L.) G. Don

Chitosan nanoparticles (CSNPs) are non-toxic and biodegradable stimulants of growth and secondary metabolite production, which offer new routes to combat plant stress. Salinity is a common and significant abiotic stress that adversely affects plant growth and development. The possible benefits of CSNPs in salt stress mitigation have not yet been reported in Catharanthus roseus, an important source of anticancer alkaloids. Plants were exposed to 150 mM NaCl as a salt stress treatment, while CSNPs were applied as a foliar spray at 1% concentration. Plant growth was considerably impaired under salt stress conditions; however, CSNPs treatment significantly reversed this effect. Specifically, CSNPs retarded chlorophyll reduction and induced activities of catalase, ascorbate peroxidase, and glutathione reductase. Thus, CSNPs alleviated the oxidative stress, indicated by lower levels of malondialdehyde and H₂O₂, thereby enabling membrane function retention and enhancing salt tolerance. Higher alkaloid accumulation was observed in salt-stressed plants following CSNP spraying than in controls. Interestingly, the expression levels of mitogen-activated protein kinases (MAPK3), geissoschizine synthase (GS), and octadecanoid-derivative responsive AP2-domain (ORCA3) genes were significantly elevated in salt-stressed plants sprayed with CSNPs. Overall, CSNP treatment overcame the deleterious effects of salinity in C. roseus by activating the antioxidant defense system, which helps to scavenge reactive oxygen species, and inducing expression of MAPK3, GS, and ORCA3 genes, thus, leading to higher alkaloid accumulation and better protection against salinity stress.

A vital role of chitosan nanoparticles in improvisation the drought stress tolerance in Catharanthus roseus (L.) through biochemical and gene expression modulation

Drought is a main abiotic stress that restricts plant growth and development. The increased global demand of anti-cancer alkaloids extracted from periwinkle (Catharanthus roseus) is mainly related to plant growth and development, which are severely affected by drought. Chitosan nanoparticles (CSNPs) have been used to boost plant growth and defense mechanism, however their impact to alleviate drought stress of C. roseus has not been investigated yet. In this study, control and stressed plants (100 and 50% of field capacity [FC], respectively) were subjected to CSNPs application at 1%. Drought stress considerably reduced plant growth, relative water content (RWC), stomatal conductance and total chlorophyll; however, CSNPs mitigated these effects. They enhanced proline accumulation and the activity of catalase (CAT) and ascorbate peroxidase (APX) with possible mitigation of drought-induced oxidative stress. Therefore, they reduced H₂O₂ and malondialdehyde (MDA) accumulation, and eventually preserved membrane integrity. Drought stress increased alkaloid accumulation, and further increase was observed with the application of CSNPs. High alkaloid content was associated with induced gene expression of strictosidine synthase (STR), deacetylvindoline-4-O-acetyltransferase (DAT), peroxidase 1 (PRX1) and geissoschizine synthase (GS) up to 5.6 folds under drought stress, but more accumulation was noticed with the application of CSNPs. Overall, this study is the first on using CSNPs to mitigate drought stress of C. roseus by inducing the antioxidant potential and gene expression of alkaloid biosynthesis.

Chitosan-, alginate- carrageenan-derived oligosaccharides stimulate defense against biotic and abiotic stresses, and growth in plants: A historical perspective

During the last 20 years, the mechanisms involved in the stimulation of defense against pathogens, and growth triggered by chitosan-, alginate- and carrageenan-derived oligosaccharides have been studied in plants. Oligo-chitosan stimulate protection against pathogens by activation of salicylic acid (SA) or jasmonic acid/ethylene (JA/ET)-dependent pathways, protection against abiotic stress through abscisic acid (ABA)-dependent pathway, and growth by increasing photosynthesis, auxin and gibberellin content, C and N assimilation, and synthesis of secondary metabolites with antipathogenic and medicinal properties. Oligo-alginates stimulate protection against pathogens through SA-dependent pathway, abiotic stress via ABA-dependent pathway, and growth by increasing photosynthesis, auxin and gibberellins contents, C and N assimilation, and synthesis of secondary metabolites with antipathogenic and medicinal properties. Oligo-carrageenan increased protection against pathogens through JA/ET, SA- and Target of Rapamycin (TOR)-dependent pathways, and growth by activation of TOR-dependent pathway leading to an increase in expression of genes involved in photosynthesis, C, N, S assimilation, and enzymes that synthesize phenolic compounds and terpenes having antipathogenic activities. Thus, the latter oligosaccharides induce similar biological effects, but through different signaling pathways in plants.

Nanochitin whisker enhances insecticidal activity of chemical pesticide for pest insect control and toxicity

BACKGROUND

Nanomaterials in plant protection promise many benefits over conventional pesticide products. Nano-enabled pesticides may alter the functionality or risk profile of active ingredients. Cationic nanochitin whiskers (NC) possess strong biological activity against wheat aphids. However, toxicity and synergistic effects of NC with chemical pesticides against pest insects has not been systemically reported. This study investigated the insecticidal enhancement by NC with Omethoate (40% EC), Imidacloprid (10% WP), and Acetamiprid (40% WG) for pest control using wheat aphid as piercing-sucking mouthparts insect. Fluorescein isothiocyanate labelled NC was used to monitor the uptake and transportation pathway of NC inside the target insects. Toxicity of NC was tested with Sprague-Dawley (SD) rat. Our findings provide a theoretical basis for future application of NC in plant protection against pest insects.

RESULTS

NCs synthesized by acidic hydrolysis were rod-like nanoparticles in a range of 50-150 nm in length and 30-50 nm in width, which examined by electron microscopy and dynamic light scattering methods. The charge density and zeta potential were about 63 mmol/kg and + 36.4 mV, respectively. By absorption and/or contact action of 30-50 mg/L of NC suspension, the corrected mortality of wheat aphids reached up to 80% or above after 12 h treatment, NC could be distributed through digestive system and relocated from mouth to other tissues inside the insect body. When associated with dilutions of conventional pesticides, the corrected mortality were significantly increased up to 95% or above. The dosage of the chemical pesticide and nanochitin in the mixtures (1:1 by volume) were all reduced to half. The acute oral toxicity Lethal Dose 50% (LD₅₀) to SD rat is greater than 5000 mg/kg BW (body weight) in male and female, acute dermal toxicity LD₅₀ is greater than 2000 mg/kg BW of NC.

CONCLUSIONS

NC has a strong promotive effect on insecticidal effectiveness of chemical insecticides. It was easily absorbed by plant, transported and distributed from mouth to other tissues of the insects while sucking plant fluid. Low acute oral and dermal toxicity to SD rat indicated that it is safe to apply in agriculture and food industry. NCs has a great potential for water-based nanopesticide formulation to reduce chemical pesticide use for future agro-environmental sustainability.

Welan gum promoted the growth of rice seedlings by enhancing carbon and nitrogen assimilation

Based on the characteristics of natural polysaccharides in film-forming, chelating, and environmental friendly, a natural polysaccharide fertilizer agent was selected to increase the utilization of nitrogen fertilizer and increase plant growth. Five polysaccharides: xanthan gum, guar gum, fenugreek gum, welan gum and chitosan were screened for plant growth promoting effect. The results showed that welan gum had the most significant effect on promoting the growth of rice seedlings, and the concentrations of 0.1 mg mL^-1 and 0.15 mg mL^-1 showed the best growth effects. The effects of welan gum on nitrogen utilization in rice seedlings were investigated. Results showed welan gum increased the contents of ammonium, nitrate, free amino acids, and proteins in rice seedlings. There were four key enzymes of nitrogen metabolism which are nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase significantly enhanced by welan gum though up-regulating the transcriptional levels of these enzymes. Therefore, nitrogen uptake and nitrogen metabolism in rice seedlings were promoted to increase the biomass of rice seedlings. Based on the research, results showed that welan gum could constitute a promising fertilizer in the future.

Chitin and Chitosan Fragments Responsible for Plant Elicitor and Growth Stimulator

Chitin and chitosan are natural polysaccharides with huge application potential in agriculture, such as promoting plant growth, eliciting plant resistance against biotic and abiotic stress, and activating symbiotic signaling between plants and beneficial microorganisms. Chitin and chitosan offer a sustainable alternative for future crop production. The bioactivities of chitin and chitosan closely depend on their structural factors, including molecular size, degree of acetylation, and pattern of acetylation. It is of great significance to identify the key fragments in chitin and chitosan chains that are responsible for these agricultural bioactivities. Herein, we review the recent progress in the structure-function relationship of chitin and chitosan in the field of agriculture application. The preparation of chitin and chitosan fragments and their action mode for plant protection and growth are also discussed.

Chitosan regulates metabolic balance, polyamine accumulation, and Na+ transport contributing to salt tolerance in creeping bentgrass

BACKGROUND

Chitosan (CTS), a natural polysaccharide, exhibits multiple functions of stress adaptation regulation in plants. However, effects and mechanism of CTS on alleviating salt stress damage are still not fully understood. Objectives of this study were to investigate the function of CTS on improving salt tolerance associated with metabolic balance, polyamine (PAs) accumulation, and Na+ transport in creeping bentgrass (Agrostis stolonifera).

RESULTS

CTS pretreatment significantly alleviated declines in relative water content, photosynthesis, photochemical efficiency, and water use efficiency in leaves under salt stress. Exogenous CTS increased endogenous PAs accumulation, antioxidant enzyme (SOD, POD, and CAT) activities, and sucrose accumulation and metabolism through the activation of sucrose synthase and pyruvate kinase activities, and inhibition of invertase activity. The CTS also improved total amino acids, glutamic acid, and γ-aminobutyric acid (GABA) accumulation. In addition, CTS-pretreated plants exhibited significantly higher Na+ content in roots and lower Na+ accumulation in leaves then untreated plants in response to salt stress. However, CTS had no significant effects on K+/Na+ ratio. Importantly, CTS enhanced salt overly sensitive (SOS) pathways and also up-regulated the expression of AsHKT1 and genes (AsNHX4, AsNHX5, and AsNHX6) encoding Na+/H+ exchangers under salt stress.

CONCLUSIONS

The application of CTS increased antioxidant enzyme activities, thereby reducing oxidative damage to roots and leaves. CTS-induced increases in sucrose and GABA accumulation and metabolism played important roles in osmotic adjustment and energy metabolism during salt stress. The CTS also enhanced SOS pathway associated with Na+ excretion from cytosol into rhizosphere, increased AsHKT1 expression inhibiting Na+ transport to the photosynthetic tissues, and also up-regulated the expression of AsNHX4, AsNHX5, and AsNHX6 promoting the capacity of Na+ compartmentalization in roots and leaves under salt stress. In addition, CTS-induced PAs accumulation could be an important regulatory mechanism contributing to enhanced salt tolerance. These findings reveal new functions of CTS on regulating Na+ transport, enhancing sugars and amino acids metabolism for osmotic adjustment and energy supply, and increasing PAs accumulation when creeping bentgrass responds to salt stress.

Recognition Pattern, Functional Mechanism and Application of Chitin and Chitosan Oligosaccharides in Sustainable Agriculture

Background:

Application of chitin attracts much attention in the past decades as the second abundant polysaccharides in the world after cellulose. Chitin oligosaccharides (CTOS) and its deacetylated derivative chitosan oligosaccharides (COS) were shown great potentiality in agriculture by enhancing plant resistance to abiotic or biotic stresses, promoting plant growth and yield, improving fruits quality and storage, etc. Those applications have already served huge economic and social benefits for many years. However, the recognition mode and functional mechanism of CTOS and COS on plants have gradually revealed just in recent years.

Objective:

Recognition pattern and functional mechanism of CTOS and COS in plant together with application status of COS in agricultural production will be well described in this review. By which we wish to promote further development and application of CTOS and COS–related products in the field.

The Use of Chitosan, Alginate, and Pectin in the Biomedical and Food Sector-Biocompatibility, Bioadhesiveness, and Biodegradability

Nowadays, biopolymers as intelligent and active biopolymer systems in the food and pharmaceutical industry are of considerable interest in their use. With this association in view, biopolymers such as chitosan, alginate, pectin, cellulose, agarose, guar gum, agar, carrageenan, gelatin, dextran, xanthan, and other polymers have received significant attention in recent years due to their abundance and natural availability. Furthermore, their versatile properties such as non-toxicity, biocompatibility, biodegradability, and flexibility offer significant functionalities with multifunctional applications. The purpose of this review is to summarize the most compatible biopolymers such as chitosan, alginate, and pectin, which are used for application in food, biotechnological processes, and biomedical applications. Therefore, chitosan, alginate, and pectin are biopolymers (used in the food industry as a stabilizing, thickening, capsular agent, and packaging) with great potential for future developments. Moreover, this review highlights their characteristics, with a particular focus on their potential for biocompatibility, biodegradability, bioadhesiveness, and their limitations on certain factors in the human gastrointestinal tract.

Polymerization degree-dependent changes in the effects of in vitro chitosan treatments on photosynthetic pigment, protein, and dry matter contents of Ipomoea purpurea

Morning Glory (Ipomoea purpurea (L.) Roth.) is a climbing plant known for its ornamental properties and ease of cultivation in temperate climates. Quality and colour of flowers and leaves, especially in the production of ornamentals, are important parameters both for producers and for customers. This study aimed to investigate the changes in photosynthetic pigment, protein and dry matter content of in vitro-propagated I. purpurea following chitosan treatment with different polymerization degrees (DP) and to determine the indirect effect of this biopolymer on leaves of the plant. Nodal explants of I. purpurea were cultured in medium supplemented with 5, 10 and 20 mg L−1 concentrations of a chitosan oligomers mixture with a variable degree of polymerization (DP) ranging from 2 to 15 or chitosan polymer with DP of 70. It was found that both oligomeric and polymeric chitosan treatments increased chlorophyll-a contents in the leaves when compared to the chitosan-naïve control group. Polymeric chitosan stimulated chlorophyll-b and carotenoid synthesis more effectively than the oligomer mixture. Also, 10 mg L−1 polymeric chitosan better triggered total protein production and plant dry matter content in I. purpurea. The results of this study showed that, due to their stimulatory effects on photosynthetic pigment, protein and plant dry matter production, chitosan oligomers at low concentration and polymers at moderate concentration might be considered as safe and natural biostimulants for ornamental plants which could affect the plant’s attractiveness and commercial success.

Chitosan-induced enhanced expression and activation of alternative oxidase confer tolerance to salt stress in maize seedlings

This study aimed to investigate the possible alleviating effect of chitosan on salt-induced growth retardation and oxidative stress and to elucidate whether this effect is linked to activation of mitochondrial respiration on the basis of alternative respiration in maize seedlings. Salt stress significantly reduced root length and plant height in comparison to the control, whereas foliar application of chitosan ameliorated the adverse effect of salinity to a certain degree. Moreover, chitosan resulted in plant growth promotion as compared to unstressed seedlings. The separate applications of chitosan and salt had a stimulatory effect on the activities of antioxidant enzymes; however, combined application of chitosan and salt were more effective than that of chitosan or salt alone. Similarly, mitochondrial total respiration rate (V_t) and alternative respiration capacity (V_alt) were increased by separate applications of chitosan and salt; however, the combination of chitosan and salt gave the highest values for these parameters. The highest values of V_alt/V_t was recorded at seedlings treated with salt plus chitosan. Similarly, cytochrome respiration capacity was also increased by chitosan in both stress-free and stressed conditions. In addition, AOX1, encoding alternative oxidase, was significantly upregulated by chitosan and/or salt. The maximum transcript level was recorded at seedlings treated with salt plus chitosan. Chitosan also significantly decreased superoxide anion and hydrogen peroxide contents and lipid peroxidation level under normal and the stressed conditions. These results suggest that the mitigating effect of chitosan on salt stress is linked to activation of alternative respiration at biochemical and molecular level.

The foliar application of a mixture of semisynthetic chitosan derivatives induces tolerance to water deficit in maize, improving the antioxidant system and increasing photosynthesis and grain yield

Research has shown that chitosan induces plant stress tolerance and protection, but few studies have explored chemical modifications of chitosan and their effects on plants under water stress. Chitosan and its derivatives were applied (isolated or in mixture) to maize hybrids sensitive to water deficit under greenhouse conditions through foliar spraying at the pre-flowering stage. After the application, water deficit was induced for 15 days. Analyses of leaves and biochemical gas exchange in the ear leaf were performed on the first and fifteenth days of the stress period. Production attributes were also analysed at the end of the experiment. In general, the application of the two chitosan derivatives or their mixture potentiated the activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase at the beginning of the stress period, in addition to reducing lipid peroxidation (malonaldehyde content) and increasing gas exchange and proline contents at the end of the stress period. The derivatives also increased the content of phenolic compounds and the activity of enzymes involved in their production (phenylalanine ammonia lyase and tyrosine ammonia lyase). Dehydroascorbate reductase and compounds such as total soluble sugars, total amino acids, starch, grain yield and harvest index increased for both the derivatives and chitosan. However, the mixture of derivatives was the treatment that led to the higher increase in grain yield and harvest index compared to the other treatments. The application of semisynthetic molecules derived from chitosan yielded greater leaf gas exchange and a higher incidence of the biochemical conditions that relieve plant stress.

The Stimulatory Effects of Nanochitin Whisker on Carbon and Nitrogen Metabolism and on the Enhancement of Grain Yield and Crude Protein of Winter Wheat

Nanochitin whisker (NC) with a cationic nature could enhance plant photosynthesis, grain yield, and quality of wheat, but have not been systematically studied. This study was designed to investigate the stimulatory effects of NC on dry matter (DM) and nitrogen (N) accumulation and translocation, and on the metabolism of carbon (C) and N in later growth stages of winter wheat to reveal the enhancement mechanism of grain yield and crude protein concentration. Different parts of NC-treated plants from pot grown experiments were collected at the pre- and post-anthesis stages. The accumulation, translocation, and contributions of DM and N from pre-anthesis vegetation organs to grains, as well as key metabolic enzyme activities, including sucrose phosphate synthase (SPS) and phosphoenolpyruvate carboxylase (PEPC), were examined. The results showed that, at an application rate of 6 mg·kg⁻¹ of NC in the soil, the accumulation of DM and N were significantly enhanced by 16.2% and 38.8% in pre-anthesis, and by 15.4% and 30.0% in post-anthesis, respectively. Translocation of N and DM in the post-anthesis periods were enhanced by 38.4% and 50.9%, respectively. NC could also stimulate enzyme activities, and increased 39.8% and 57.1% in flag leaves, and by 36.0% and 58.8% in spikes, respectively, at anthesis. SPS and PEPC increased by 28.2% and 45.1% in flag leaves, and by 42.2% and 56.5% in spikes, respectively, at 15 days after anthesis. The results indicated that the NC promoted N metabolism more than C metabolism, and resulted in the enhancement of grain yield by 27.56% and of crude protein concentration in grain by 13.26%, respectively.

Polysaccharides from Grateloupia filicina enhance tolerance of rice seeds (Oryza sativa L.) under salt stress

Rice (Oryza sativa L.) is a salt-sensitive crop which could be suppressed seriously by salt stress at germination stage. Some seaweeds polysaccharides could enhance plants resistance but there is little research about polysaccharides from Grateloupia filicina in agriculture. Therefore, G. filicina polysaccharide (GFP) and low molecular weight (MW) G. filicina polysaccharide (LGFP) were applied to rice seeds under salt stress (GFP: 2093.4 kDa, LGFP-1: 40.8 kDa, LGFP-2: 22.6 kDa, LGFP-3: 5.1 kDa, LGFP-4: 3.0 kDa). Relatively low MW polysaccharides LGFP1-4 showed better effect than GFP, and LGFP-1 showed the best effect on germination potential, germination index, shoot/root length and vigor index than negative control by 26.67, 14.27, 30.50, 202.65 and 162.78%, respectively. Optimum concentration was determined at 0.1 mg/mL, and LGFP-1 increased proline content, superoxide dismutase (SOD) and peroxidase activities (POD) which improved ability of osmotic adjustment and reactive oxygen species (ROS) scavenging. FITC-labeled LGFP-1 (F-LGFP-1) was to investigate the polysaccharide absorption and it was be observed in root and shoot with different distribution. Finally, expression of Na⁺/H⁺ antiporter gene was up regulated which suggested LGFP-1 could protect rice seeds by regulating Na⁺ content. This research showed potential application of polysaccharides from G. filicina for increasing rice seeds salt tolerance.

The Sugar-Signaling Hub: Overview of Regulators and Interaction with the Hormonal and Metabolic Network

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future.

The Sugar-Signaling Hub: Overview of Regulators and Interaction with the Hormonal and Metabolic Network

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future.

miRNA and mRNA Expression Profiles Reveal Insight into Chitosan-Mediated Regulation of Plant Growth

Chitosan has been numerously studied as a plant growth regulator and stress tolerance inducer. To investigate the roles of chitosan as bioregulator on plant and unravel its possible metabolic responses mechanisms, we simultaneously investigated mRNAs and microRNAs (miRNAs) expression profiles of wheat seedlings in response to chitosan heptamer. We found 400 chitosan-responsive differentially expressed genes, including 268 up-regulated and 132 down-regulated mRNAs, many of which were related to photosynthesis, primary carbon and nitrogen metabolism, defense responses, and transcription factors. Moreover, miRNAs also participate in chitosan-mediated regulation on plant growth. We identified 87 known and 21 novel miRNAs, among which 56 miRNAs were induced or repressed by chitosan heptamer, such as miRNA156, miRNA159a, miRNA164, miRNA171a, miRNA319, and miRNA1127. The integrative analysis of miRNA and mRNA expression profiles in this case provides fundamental information for further investigation of regulation mechanisms of chitosan on plant growth and will facilitate its application in agriculture.