Trans-aconitic acid inhibits the growth and photosynthesis of Glycine max

Rapid Identification of Phytotoxins Produced by Glomerella cingulata Using High-Resolution Mass Spectrometry-Based Qualification, Targeted Structural Confirmation and Their Characteristics Investigation

Glomerella cingulata is a pathogenic fungus that can cause apple Glomerella leaf spot (GLS), a new and destructive apple disease in China. Phytotoxins are important factors closely related to the disease process, but there is still no report on the phytotoxins of G. cingulata. The aim of this study was to rapidly identify the phytotoxins of this pathogen using a strategy of HRMS-based preliminary qualification, followed by targeted structure confirmation and also investigation of phytotoxicity characteristics. First, the crude toxin sample was directly analyzed by the UPLC-HRMS and GC-MS, and the data were processed to screen for possible phytotoxic compounds using MS library and the phytotoxicity-related literature. The reference standards of credible phytotoxic compounds were then subjected to targeted structure validation (signal comparison between standards and compounds in crude toxin via HPLC-DAD, UPLC-MS/MS, and GC-MS), and also the phytotoxicity assay. The results confirmed six phytotoxins produced by G. cingulata, namely 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-bis(hydroxymethyl)furan (BHMF), 2-furoic acid (FA), 2,3-butanediol, trans-aconitic acid (TAA), and cis-aconitic acid (CAA). Of these, HMFCA and TAA exhibited greater phytotoxicity. Main characteristics: All of them were non-host-selective toxins, and toxins were synergistically phytotoxic to the host when mixed. BHMF, HMFCA, FA, TAA, and CAA could be commonly produced by all tested strains, and their phytotoxicity can be significantly inhibited or even eliminated at high temperatures or high pH. The elucidation of the phytotoxins of G. cingulata in this work could provide information on the pathogenesis and control of apple GLS.

Terpinen-4-ol from tea tree oil prevents Aspergillus flavus growth in postharvest wheat grain

Plant volatile organic compounds (PVOCs) have gained increasing attention for their role in preventing fungal spoilage and insect contamination in postharvest agro-products owing to their effectiveness and sustainability. In this study, the essential oil was extracted from fresh M. alternifolia (tea tree) leaves, and the fumigation vapor of tea tree oil (TTO) completely inhibited the growth of Aspergillus flavus on agar plates at a concentration of 1.714 μL/mL. Terpinen-4-ol was identified as the major component (40.76 %) of TTO volatiles analyzed using headspace gas chromatography-mass spectrometry. Terpinen-4-ol vapor completely inhibited the A. flavus growth on agar plates and 20 % moisture wheat grain at 0.556 and 1.579 μL/mL, respectively, indicating that terpinen-4-ol serves as the main antifungal constituent in TTO volatiles. The minimum inhibitory concentration of terpinen-4-ol in liquid-contact culture was 1.6 μL/mL. Terpinen-4-ol treatment caused depressed, wrinkled, and punctured mycelial morphology and destroyed the plasma membrane integrity of A. flavus. Metabolomics analysis identified significant alterations in 93 metabolites, with 79 upregulated and 14 downregulated in A. flavus mycelia exposed to 1.6 μL/mL terpinen-4-ol for 6 h, involved in multiple cellular processes including cell membrane permeability and integrity, the ABC transport system, pentose phosphate pathway, and the tricarboxylic acid cycle. Biochemical analysis and 2,7-dichlorofluorescein diacetate staining showed that terpinen-4-ol induced oxidative stress and mitochondrial dysfunction in A. flavus mycelia. This study provides new insights into the antifungal effects of the main TTO volatile compounds terpinen-4-ol on the growth of A. flavus.

A broad assessment of Eremurus spectabilis M. Bieb: chemical and elemental composition, total phenolic and antimicrobial activity analysis, and quantum chemical calculations of radical scavenging potential

Eremurus spectabilis M. Bieb was extensively investigated experimentally and theoretically, including the antioxidant properties of compounds such as flavonoids, hydroxycinnamic acid derivatives, hydroxybenzoic acid derivatives, and organic acids. Antioxidant activity was investigated using the Density Functional Theory (DFT) method based on three known mechanisms: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET). Subcritical water extraction (SWE), soxhlet extraction (SE), and solvent extraction (SOE) techniques were applied in the extraction process. Malic acid was the major compound with an extract concentration of 38,532.84 ± 1849.58 µg analyte/kg, total phenolics, and free radical scavenging activity were 10.67 mg gallic acid/mL extract and 73.89% per mg/mL extract, respectively. P, Fe, Na, Mg, K, and Ca were the main elements. The antibacterial activity of E. spectabilis against seven bacteria was evaluated, and it was found to be higher than the commercial antibiotics P10 and AMC30.

Accumulation patterns of tobacco root allelopathicals across different cropping durations and their correlation with continuous cropping challenges

Introduction

Continuous cropping challenges have gradually emerged as pivotal factors limiting the sustainable development of agricultural production. Allelopathicals are considered to be the primary obstacles. However, there is limited information on allelopathic accumulation across various continuous cropping years and its correlation with the associated challenges.

Methods

Tobacco was subjected to varying planting durations: 1 year (CR), 5 years (CC5), 10 years (CC10), and 15 years (CC15).

Results

Our findings unveiled discernible disparities in tobacco growth patterns across diverse continuous cropping periods. Notably, the most pronounced challenges were observed in the CC5 category, characterized by yield reduction, tobacco black shank outbreaks, and a decline in beneficial flora. Conversely, CC15 exhibited a substantial reduction in challenges as the continuous cropping persisted with no significant differences when compared to CR. Within the tobacco rhizosphere, we identified 14 distinct allelopathic compounds, with 10 of these compounds displaying noteworthy variations among the four treatments. Redundancy analysis (RDA) revealed that eight allelopathic compounds exhibited autotoxic effects on tobacco growth, with MA, heptadecanoic acid, and VA ranking as the most potent inhibitors. Interaction network highlighted the pivotal roles of VA and EA in promoting pathogen proliferation and impeding the enrichment of 13 beneficial bacterial genera. Furthermore, a structural equation model elucidated that MA and EA primarily exert direct toxic effects on tobacco, whereas VA fosters pathogen proliferation, inhibits the enrichment of beneficial bacteria, and synergistically exacerbates the challenges associated with continuous cropping alongside EA.

Discussion

These findings suggested discernible disparities in tobacco growth patterns across the various continuous cropping periods. The most pronounced challenges were observed in CC5, whereas CC15 exhibited a substantial reduction in challenges as continuous cropping persisted. VA may play a pivotal role in this phenomenon by interacting with pathogens, beneficial bacterial genera, and EA.

Allelopathy: an alternative tool for sustainable agriculture

Population increase, poverty, environmental degradation, and the use of synthetic herbicides are interdependent and closely linked and hence influence global food safety and stability of world agriculture. On the one hand, varied weeds, insects, and other pests have caused a tremendous loss in agricultural crop productivity annually. On the other hand, the use of synthetic insecticides, herbicides, fungicides, and other pesticides significantly disturbed the ecology of biotic communities in agricultural and natural ecosystems. Eventually, it destroyed the ecological balance in food chains. Interestingly, natural products released by the plants (allelochemicals) are secondary metabolites involved in ecological interactions and could be an important source of alternative agrochemicals. Mainly released by the plants as an outcome of acquaintances with other plants in their vicinity, these allelochemicals can also be used as eco-friendly substitutes for synthetic herbicides and other pesticides. Despite these facts, agrochemicals are either preferred over allelochemicals or the latter are not known in the direction of their use in achieving sustainability in agriculture. Given this, considering recent reports, this paper aims to: (1) emphasize allelochemicals; (2) overview the major biochemistry of allelochemicals; (3) critically discuss the role of allelopathy (and underlying major mechanisms) in the management of noxious weeds, insect pests, and major plant pathogens; and (4) enlighten the significant aspects so far not or least explored in the current context.

Response mechanisms of sugarcane seedlings to the allelopathic effects of root aqueous extracts from sugarcane ratoons of different ages

Sugarcane ratoon performance declines with increasing age due to the intergenerational accumulation and release of allelochemicals by old sugarcane roots. We aimed to clarify the effects of these allelochemicals on sugarcane seedling growth under continuous sugarcane ratoon cropping. We investigated the allelopathic effects of treatment with root aqueous extracts from sugarcane ratoons of different ages on the osmoregulatory substance content, antioxidant enzyme activity, membrane lipid peroxidation product content, photosynthetic physiological characteristics, and root exudate enzymatic characteristics of sugarcane seedlings. The root aqueous extracts exerted allelopathic effects on sugarcane seedlings. The relative electrolyte leakage, proline content, soluble protein content, soluble sugar content, malondialdehyde content, and catalase activity of the leaves were more sensitive than those of the roots. Conversely, the superoxide dismutase and peroxidase activities of the roots (positive response) were more sensitive than those of the leaves (negative response). The total chlorophyll content and net photosynthetic rate of the leaves exhibited relatively sensitive negative responses. Urease activity negatively responded but sucrase activity positively responded. We concluded that the root aqueous extracts of sugarcane ratoons may exert their allelopathic effects by affecting the level of osmoregulatory substances and causing peroxidative damage to the cell membranes of sugarcane seedlings and altering the activities of various enzymes in the rhizosphere.

Multi-omic characterization of bifunctional peroxidase 4-coumarate 3-hydroxylase knockdown in Brachypodium distachyon provides insights into lignin modification-associated pleiotropic effects

A bifunctional peroxidase enzyme, 4-coumarate 3-hydroxylase (C3H/APX), provides a parallel route to the shikimate shunt pathway for the conversion of 4-coumarate to caffeate in the early steps of lignin biosynthesis. Knockdown of C3H/APX (C3H/APX-KD) expression has been shown to reduce the lignin content in Brachypodium distachyon. However, like many other lignin-modified plants, C3H/APX-KDs show unpredictable pleiotropic phenotypes, including stunted growth, delayed senescence, and reduced seed yield. A system-wide level understanding of altered biological processes in lignin-modified plants can help pinpoint the lignin-modification associated growth defects to benefit future studies aiming to negate the yield penalty. Here, a multi-omic approach was used to characterize molecular changes resulting from C3H/APX-KD associated lignin modification and negative growth phenotype in Brachypodium distachyon. Our findings demonstrate that C3H/APX knockdown in Brachypodium stems substantially alters the abundance of enzymes implicated in the phenylpropanoid biosynthetic pathway and disrupt cellular redox homeostasis. Moreover, it elicits plant defense responses associated with intracellular kinases and phytohormone-based signaling to facilitate growth-defense trade-offs. A deeper understanding along with potential targets to mitigate the pleiotropic phenotypes identified in this study could aid to increase the economic feasibility of lignocellulosic biofuel production.

Aconitic Acid Recovery from Renewable Feedstock and Review of Chemical and Biological Applications

Aconitic acid (propene-1,2,3-tricarboxylic acid) is the most prevalent 6-carbon organic acid that accumulates in sugarcane and sweet sorghum. As a top value-added chemical, aconitic acid may function as a chemical precursor or intermediate for high-value downstream industrial and biological applications. These downstream applications include use as a bio-based plasticizer, cross-linker, and the formation of valuable and multi-functional polyesters that have also been used in tissue engineering. Aconitic acid also plays various biological roles within cells as an intermediate in the tricarboxylic acid cycle and in conferring unique survival advantages to some plants as an antifeedant, antifungal, and means of storing fixed pools of carbon. Aconitic acid has also been reported as a fermentation inhibitor, anti-inflammatory, and a potential nematicide. Since aconitic acid can be sustainably sourced from renewable, inexpensive sources such as sugarcane, molasses, and sweet sorghum syrup, there is enormous potential to provide multiple streams of additional income to the sugar industry through downstream industrial and biological applications that we discuss in this review.

Searching Hit Potential Antimicrobials in Natural Compounds Space against Biofilm Formation

Biofilms are communities of microorganisms that can colonize biotic and abiotic surfaces and thus play a significant role in the persistence of bacterial infection and resistance to antimicrobial. About 65% and 80% of microbial and chronic infections are associated with biofilm formation, respectively. The increase in infections by multi-resistant bacteria instigates the need for the discovery of novel natural-based drugs that act as inhibitory molecules. The inhibition of diguanylate cyclases (DGCs), the enzyme implicated in the synthesis of the second messenger, cyclic diguanylate (c-di-GMP), involved in the biofilm formation, represents a potential approach for preventing the biofilm development. It has been extensively studied using PleD protein as a model of DGC for in silico studies as virtual screening and as a model for in vitro studies in biofilms formation. This study aimed to search for natural products capable of inhibiting the Caulobacter crescentus enzyme PleD. For this purpose, 224,205 molecules from the natural products ZINC15 database, have been evaluated through molecular docking and molecular dynamic simulation. Our results suggest trans-Aconitic acid (TAA) as a possible starting point for hit-to-lead methodologies to obtain new inhibitors of the PleD protein and hence blocking the biofilm formation.