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High concentrations of environmental ammonia can cause reduced immunity and death in fish, causing enormous economic losses. Air‐breathing fish usually have a high ammonia tolerance and are very suitable for high‐density fish farming. However, research on the effects of environmental ammonia on air‐breathing fish immunity is lacking. Therefore, this study investigated the effects of environmental ammonia on the immunity of large‐scale loach (Paramisgurnus dabryanus) by exposing fish to 30 mmol/L NH4Cl solution and subsequently analyzing the changes in serum and liver immune indicators, including total protein, albumin, globulin, immunoglobulin (Ig) M, lysozyme, complement component (C) 3 and C4, heat shock protein (HSP) 70, HSP90, tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, IL‐6, and IL‐12. Results revealed that ammonia exposure significantly affected the total protein, albumin, globulin, IgM, complement C3 and C4, HSP70, HSP90, and inflammatory cytokine contents in the body, indicating that ammonia exposure induced a significant immune response and lowered bodily immunity. However, most of the immune indicators significantly decreased in the later stages of the experiment, suggesting a weakened immune response, which may be due to the species‐specific ammonia detoxification ability of large‐scale loach that reduces ammonia toxicity in the body. This study demonstrated the effects of high concentration of environmental ammonia on the immune response in Paramisgurnus dabryanus. Species‐specific ammonia detoxification strategies in P. dabryanus could weaken the immune response induced by high environmental ammonia.

Background As the predominant secondary metabolic pathway in tea plants, flavonoid biosynthesis increases with increasing temperature and illumination. However, the concentration of most flavonoids decreases greatly in light-sensitive tea leaves when they are exposed to light, which further improves tea quality. To reveal the metabolism and potential functions of flavonoids in tea leaves, a natural light-sensitive tea mutant ( Huangjinya ) cultivated under different light conditions was subjected to metabolomics analysis. Results The results showed that chlorotic tea leaves accumulated large amounts of flavonoids with ortho-dihydroxylated B-rings (e.g., catechin gallate, quercetin and its glycosides etc.), whereas total flavonoids (e.g., myricetrin glycoside, epigallocatechin gallate etc.) were considerably reduced, suggesting that the flavonoid components generated from different metabolic branches played different roles in tea leaves. Furthermore, the intracellular localization of flavonoids and the expression pattern of genes involved in secondary metabolic pathways indicate a potential photoprotective function of dihydroxylated flavonoids in light-sensitive tea leaves. Conclusions Our results suggest that reactive oxygen species (ROS) scavenging and the antioxidation effects of flavonoids help chlorotic tea plants survive under high light stress, providing new evidence to clarify the functional roles of flavonoids, which accumulate to high levels in tea plants. Moreover, flavonoids with ortho-dihydroxylated B-rings played a greater role in photo-protection to improve the acclimatization of tea plants.

In this work, the efficiency of chitosan as a biocontrol agent against Fusarium solani on tomato plants was determined and the antifungal activity and the induction of defence enzymes were evaluated. Treatments were carried out with different concentrations of chitosan (1, 2 and 3 g L−1) combined with a synthetic fungicide (carbendazim). The results showed that all chitosan treatments significantly inhibited the mycelial growth and biomass of F. solani, with the most effective results obtained with the 3 g L−1 treatment. Scanning electron microscopy revealed that chitosan causes severe structural damage to F. solani, including cell lysis and the deformation of mycelium and spores. In addition, plants treated with chitosan showed significant improvements in height, stem diameter, root dry biomass and root length compared to those treated with synthetic fungicide and the control (no chitosan application). Enzyme assays showed that chitosan significantly increased superoxide dismutase, catalase, peroxidase and phenylalanine ammonia-lyase activity, indicating an increased defensive response. These results suggest that chitosan is a viable and less toxic alternative for the management of disease caused by F. solani in tomato plants, promoting both plant health and growth.

Plants are equipped with a wide range of defensive mechanisms such as morphophysiological, biochemical, molecular, and hormonal signaling for protecting against insect-pest infestation. The infestation of a devastating pest shoot fly [Atherigona soccata (Rodani)] at seedling stage causes huge loss of sorghum crop productivity. In morphophysiological screening ICSV700, ICSV705, and IS18551 have been categorized as resistant, PSC-4 moderately resistant, SL-44 and SWARNA as susceptible. The present study focused on the role of defensive gene expression and its products viz: superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), polyphenol oxidase (PPO), phenyl alanine ammonia lyase (PAL), responsive enzymes, and metabolites restoring redox status in sorghum plants against shoot fly infestation. In both leaf and stem tissue of sorghum genotypes, shoot fly infestation induced SOD, APX, DHAR, GR, PAL, and PPO activities while CAT activity was significantly declined at 15 and 21 days after emergence (DAE). IS18551 with resistant behavior showed upregulation of SOD, GR, APX, and DHAR along with accumulation of ascorbate, glutathione enhancing redox status of the plant during shoot fly infestation at later stage of infestation. While SWARNA with susceptible response exhibited enhanced activity of phenylpropanoid pathway enzymes PAL and PPO which in turn increased the levels of secondary metabolites like o-dihydroxyphenol and other phenols deterring the insect to attack the plant. The qRT-PCR data predicted that stress-responsive genes were initially unregulated in SWARNA; however, at 21 DAE, multifold higher expression of SOD, CAT, APX, and PPO (24.8-, 37.2-, 21.7-, and 17.9-fold respectively) in 1S18551 indicates the resistance behavior of this genotype against insect infestation owing to sustainable development capability.

Herbivory damage leads to induction of rapid signals and responses in plants such as oxidative burst, accumulation of secondary metabolites and defensive proteins. Response of various defensive enzymes and secondary metabolites in flag leaf samples of six bread wheat varieties against aphid feeding was investigated. Six bread wheat varieties, namely PBW 621 and HD 2967 (timely sown irrigated), PBW 590 and PBW 658 (late sown irrigated), and PBW 644 and PBW 660 (timely sown rainfed) were grown under the aphid infested and uninfested conditions and were sampled at a regular interval to analyze the biochemical changes caused by aphid feeding. A tremendous increase in the overall activity of various enzymes namely superoxide dismutase, glutathione reductase, phenylalanine ammonia lyase and polyphenol oxidase was observed, all of which play an important role in plants defense towards aphid feeding. Each wheat genotype showed an overall difference in their defensive activity towards aphid feeding. However, certain genotypes under different conditions showed significantly less susceptibility towards aphid damage.Abbreviations: GR: glutathione reductase; HPR: host plant resistance; PAL: phenylalanine ammonia lyase; PPO: poly phenol oxidase; POD: peroxidase; SOD: superoxide dismutase

Leaf spot disease caused by Alternaria pathogens seriously threatens peony production. The physiological mechanism of peony resistance to the pathogen is little reported. This study aimed to reveal the defensive mechanism of peonies in response to the pathogen Alternaria tenuissima. The disease-resistant (R) variety ‘Zi Fengyu’ and susceptible (S) variety ‘Heihai Botao’ were employed, and some parameters in the leaves were analyzed after inoculation with A. tenuissima, mainly including the hypersensitive response (HR), activity of defensive enzymes, and expression of disease-resistance genes. The results showed that compared with the responses in the S genotype, HR occurred more rapidly in the R genotype. Meanwhile, the activity of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) and other two defense enzymes (polyphenol oxidase and phenylalanine ammonia-lyase) increased more significantly, and the expression of pathogenesis-related (PR) genes (PlPR1, PlPR2, PlPR4B, PlPR5, and PlPR10) and two WRKY genes (PlWRKY13 and PlWRKY65) was more strongly induced. These responses collectively contributed to the disease resistance of the R genotype. These findings provided a theoretical basis for understanding the intrinsic mechanism of peony resistance to Alternaria leaf spot disease and breeding the disease-resistant peony varieties using a molecular approach.

Silicic acid (SA) is an important source of silicon (Si) that induces resistance in plants against insect pests. The present study aimed to investigate the impact of foliar spray of SA on the biological parameters of aphid, Lipaphis erysimi and the activity of defensive enzymes in rapeseed ( Brassica napus L.). The first experiment evaluated the biological parameters of L. erysimi with two treatments viz., foliar application of 0.4% SA and a control. The results indicated that the foliar spray of 0.4% SA in rapeseed significantly reduced the nymphal period, adult longevity and fecundity of L. erysimi compared to the control. In the 0.4% SA- treated rapeseed, the nymphal period, adult longevity and fecundity of L. erysimi were 7.00 days, 7.96 days and 23.52 nymphs/ female, respectively, while in the control, these were 7.92 days, 8.80 days and 26.04 nymphs/ female, respectively. Furthermore, the foliar application of 0.4% SA significantly enhanced the Si content (0.31%) in rapeseed compared to control (0.16%). The second experiment aimed to investigate the activity of plant defensive enzymes in rapeseed with four treatments: 0.4% SA alone, aphid alone, 0.4% SA + aphid and a control. The results revealed no significant changes in the activity of defense related enzymes such as peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia- lyase (PAL) in the treatments of 0.4% SA alone and the control. However, a significant increase in enzyme activities were observed in both the 0.4% SA + aphid and aphid alone treatments. Notably, the 0.4% SA + aphid exhibited higher levels of plant defensive enzymes activity compared to the aphid alone treatment, suggesting the role of Si in enhancing the defensive responses in rapeseed against L. erysimi . Additionally, this study established a significant negative correlation between Si content and biological parameters of L. erysimi .

Background and aims Ganoderma boninense causes basal stem rot disease of oil palm, a serious problem in many countries producing crude palm oil. Ganoderma penetrates host cells by producing cell wall degrading enzymes (CWDEs) and its mycelia trigger defense responses in the host plant. The soil physicochemical properties affect plant growth and soil microbes. Only limited knowledge is available on the relationship between soil characteristics and occurrence of plant diseases. Thus, this study aimed to determine soil physicochemical properties, CWDEs in rhizosphere soil, PR proteins, and defensive enzymes in plant roots, and to look for potential associations in Ganoderma -infected oil palm plantations. Methods Roots and rhizosphere soil were sampled from Ganoderma infected and non- infected oil palms from the main oil palm plantation area in southern Thailand. Spectrophotometry was used to investigate enzyme activities. Results Fungal laccase, lignin peroxidase (LiP), and manganese peroxidase (MnP) were positively correlated to organic matter (OM) and organic carbon (OC) concentrations, but these enzymes were negatively correlated to soil pH. Cellulase was sensitive to soil physicochemical properties when compared with laccase, LiP, MnP and xylanase. Regarding plant defensive enzymes, high levels of OM, OC, calcium, potassium, manganese, magnesium, nitrogen and zinc in soil were related to chitinase, β-1,3-glucanase, phenylalanine ammonia lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) synthesis in oil palms. Moreover, POD, PPO and PAL were positively correlated to fungal laccase, LiP and MnP. Conclusions Our results indicate that the relationships between fungal enzymes, defense related enzymes in host plant, and soil physicochemical properties, are involved in determining basal stem rot disease occurrence in oil palm.

Algal–bacterial granular sludge, a new biological technology, has been widely recognized due to its highly effective pollutant treatment and energy efficiency. This study investigated the effects of environmental concentrations of Cr(VI) (0.5–2.5 mg/L) on the performance of algal–bacterial granular sludge and self-defensive responses after 90 days of cultivation. The results showed that Cr(VI) affected chemical oxygen demand (COD) decrease, ammonia-N and phosphate removal, with different trends being apparent. A linear decline in COD decrease was observed, whereas an initial decrease and then increase in ammonia-N and phosphate removal took place. Algal–bacterial granular sludge effectively removed Cr(VI) from wastewater through biological adsorption and reduction, showing the potential to treat Cr(VI)-contaminated wastewater. Cr(VI) affected the community abundance of the algal–bacterial granular sludge, in which Chlorophyceae and cyanobacteria were vulnerable under Cr(VI)-induced stress. To reduce the toxicity of Cr(VI), over-produced EPS-PN and antioxidant enzymes (MDA, SOD and CAT) acted as self-defensive responses to resist oxidative damage. This study aimed to conduct a comprehensive environmental sustainability assessment of the algal–bacterial granular sludge process in treating municipal wastewater containing Cr(VI). It is hoped that this study can provide useful information for improved engineering feasibility of algal–bacterial granular sludge.

Cotton aphids (Aphis gossypii Glover) cause harm by feeding on phloem sap and spreading plant viruses to lily. Understanding the mechanisms by which aphids infest lily plants is crucial for effective aphid management and control. In this study, we investigated the activity of antioxidants, integrated nontargeted metabolomes and transcriptomes of lilies infested by cotton aphids to explore the changes in lily leaves. Overall, the results indicated that the catalase (CAT) activity in the leaves of the lily plants was greater than that in the leaves of the control plants. A comprehensive identification of 604 substances was conducted in the leaves. Furthermore, the differentially abundant metabolite analysis revealed the enrichment of phenylalanine metabolism and α-linolenic acid metabolism. Moreover, 3574 differentially expressed genes (DEGs), whose expression tended to increase, were linked to glutathione metabolism and phenylpropanoid biosynthesis. In addition, the integrated analysis revealed that the defensive response of lily leaves to aphids is manifested through antioxidant reactions, phenylpropane and flavonoid biosynthesis, and α-linolenic acid metabolism. Finally, the key metabolites were CAT, glutathione, coumaric acid, and jasmonic acid, along with the key genes chalcone synthase (CHS), phenylalanine ammonia-lyase (PAL), and 12-oxo-phytodienoic acid reductase (OPR). Accordingly, the findings of this research elucidate the molecular and metabolic reactions of A. gossypii in lily plants, offering valuable insights for developing aphid resistance strategies in lily farming.