Explore the vast range of titles available.

Andrographis paniculata (Kalmegh) has long been used across Asia, America, and Africa to treat diseases such as diabetes, high blood pressure, ulcers, leprosy, and malaria. Like all plants, it synthesizes diverse secondary metabolites through pathways such as the phenylpropanoid pathway. Key enzymes include Phenylalanine Ammonia-Lyase (PAL), which converts phenylalanine to trans-cinnamic acid, Chalcone synthase (CHS), which initiates flavonoid biosynthesis, and Dihydroflavonol-4-reductase (DFR), which reduces dihydroflavonols to leucoanthocyanidins. These metabolites provide defense against biotic and abiotic stresses due to their antioxidant and antimicrobial properties, contributing to the plant’s therapeutic value. This study profiles these metabolites and examines expression of phenylpropanoid genes using PCR. Metallothionein gene expression, linked to metal detoxification, was also analyzed, offering insights into the plant’s metabolism.

Phenylpropanoids, the largest class of natural products including flavonoids, anthocyanins, monolignols and tannins perform multiple functions ranging from photosynthesis, nutrient uptake, regulating growth, cell division, maintenance of redox homeostasis and biotic and abiotic stress responses. Being sedentary life forms, plants possess several regulatory modules that increase their performance in varying environments by facilitating activation of several signaling cascades upon perception of developmental and stress signals. Of the various regulatory modules, those involving MYB transcription factors are one of the extensive groups involved in regulating the phenylpropanoid metabolic enzymes in addition to other genes. R2R3 MYB transcription factors are a class of plant-specific transcription factors that regulate the expression of structural genes involved in anthocyanin, flavonoid and monolignol biosynthesis which are indispensable to several developmental pathways and stress responses. The aim of this review is to present the regulation of the phenylpropanoid pathway by MYB transcription factors via Phospholipase D/phosphatidic acid signaling, downstream activation of the structural genes, leading to developmental and/or stress responses. Specific MYB transcription factors inducing or repressing specific structural genes of anthocyanin, flavonoid and lignin biosynthetic pathways are discussed. Further the roles of MYB in activating biotic and abiotic stress responses are delineated. While several articles have reported the role of MYB’s in stress responses, they are restricted to two or three specific MYB factors. This review is a consolidation of the diverse roles of different MYB transcription factors involved both in induction and repression of anthocyanin, flavonoid, and lignin biosynthesis.

There is no argument to the fact that insect herbivores cause significant losses to plant productivity in both natural and agricultural ecosystems. To counter this continuous onslaught, plants have evolved a suite of direct and indirect, constitutive and induced, chemical and physical defenses, and secondary metabolites are a key group that facilitates these defenses. Polyphenols—widely distributed in flowering plants—are the major group of such biologically active secondary metabolites. Recent advances in analytical chemistry and metabolomics have provided an opportunity to dig deep into extraction and quantification of plant-based natural products with insecticidal/insect deterrent activity, a potential sustainable pest management strategy. However, we currently lack an updated review of their multifunctional roles in insect-plant interactions, especially focusing on their insect deterrent or antifeedant properties. This review focuses on the role of polyphenols in plant-insect interactions and plant defenses including their structure, induction, regulation, and their anti-feeding and toxicity effects. Details on mechanisms underlying these interactions and localization of these compounds are discussed in the context of insect-plant interactions, current findings, and potential avenues for future research in this area.

The diversity of secondary compounds in the plant kingdom is huge. About 200,000 compounds are known, which are grouped into amines, non-protein amino acids, peptides, alkaloids, glucosinolates, cyanogenic glucosides, organic acids, terpenoids, quinones, polyacetylenes, and phenolics. The group of phenolic compounds consists of polyphenols, oligophenols and monophenols or simple phenolic compounds such as benzoic and cinnamic acids and their hydroxylated derivatives. Among the thousands of compounds present in ecological interactions, simple phenolic acids are the most abundant in soils, and many are described as allelochemicals. Given the physiological and biochemical importance of these compounds, we review their biosynthesis and metabolic actions in plants.

Lignin is central to overcoming recalcitrance in the enzyme hydrolysis of lignocellulose. While the term implies a physical barrier in the cell wall structure, there are also important biochemical components that direct interactions between lignin and the hydrolytic enzymes that attack cellulose in plant cell walls. Progress toward a deeper understanding of the lignin synthesis pathway – and the consistency between a range of observations over the past 40 years in the very extensive literature on cellulose hydrolysis – is resulting in advances in reducing a major impediment to cellulose conversion: the cost of enzymes. This review addresses lignin and its role in the hydrolysis of hardwood and other lignocellulosic residues. Lignin and lignin-derived phenolic compounds inhibit lignocellulolytic enzymes. While lignin nonspecifically adsorbs enzymes, phenolic compounds inhibit and/or deactivate them. The effect will vary depending on type of phenolic compounds, their concentration, and possible synergistic effects. The effect will also depend on the type of enzyme and microorganism from which they were produced. Enzymes from Trichoderma reesei are more susceptible to the inhibitory and/or deactivating effects than those from Aspergillus niger. Noncatalytic proteins, such as bovine serum albumin or soy-derived proteins, minimize the nonspecific adsorption of the hydrolytic enzymes on lignin. Understanding these mechanisms of enzyme inhibition or deactivation and approaches to mitigate them potentially favor continued reduction of cellulose conversion-associated costs.

Pathogens hitting the plant cell wall is the first impetus that triggers the phenylpropanoid pathway for plant defense. The phenylpropanoid pathway bifurcates into the production of an enormous array of compounds based on the few intermediates of the shikimate pathway in response to cell wall breaches by pathogens. The whole metabolomic pathway is a complex network regulated by multiple gene families and it exhibits refined regulatory mechanisms at the transcriptional, post-transcriptional, and post-translational levels. The pathway genes are involved in the production of anti-microbial compounds as well as signaling molecules. The engineering in the metabolic pathway has led to a new plant defense system of which various mechanisms have been proposed including salicylic acid and antimicrobial mediated compounds. In recent years, some key players like phenylalanine ammonia lyases (PALs) from the phenylpropanoid pathway are proposed to have broad spectrum disease resistance (BSR) without yield penalties. Now we have more evidence than ever, yet little understanding about the pathway-based genes that orchestrate rapid, coordinated induction of phenylpropanoid defenses in response to microbial attack. It is not astonishing that mutants of pathway regulator genes can show conflicting results. Therefore, precise engineering of the pathway is an interesting strategy to aim at profitably tailored plants. Here, this review portrays the current progress and challenges for phenylpropanoid pathway-based resistance from the current prospective to provide a deeper understanding.

Lignin is a complex aromatic biopolymer important for providing mechanical strength to the cell wall and resistance against both biotic and abiotic stresses. It helps in plant growth by providing physical strength and helping in long distance transport of water and minerals. Lignin biosynthetic genes are known to be induced under both biotic and abiotic stresses, and perturbations in lignin biosynthesis has shown to result in changes in plants defense responses against these stresses. It’s important to understand how these sophisticated mechanisms are employed by the plants to adapt to the adverse climatic conditions and develop more resilient plant varieties. In this review, we try to deliver a thorough comprehension of how lignin biosynthesis is altered under various environmental conditions. We believe this information will be useful in understanding the role of different lignin biosynthetic genes in conferring resistance against different stresses.

Plants have evolved complex mechanisms to cope with diverse abiotic stresses, with the phenylpropanoid pathway playing a central role in stress adaptation. This pathway produces an array of secondary metabolites, particularly polyphenols, which serve multiple functions in plant growth, development, regulating cellular processes, and stress responses. Recent advances in understanding the molecular mechanisms underlying phenylpropanoid metabolism have revealed complex regulatory networks involving MYB transcription factors as master regulators and their interactions with stress signaling pathways. This review summarizes our current understanding of polyphenol-mediated stress adaptations in plants, emphasizing the regulation and function of key phenylpropanoid pathway compounds. We discussed how various abiotic stresses, including heat and chilling stress, drought, salinity, light stress, UV radiation, nanoparticles stress, chemical stress, and heavy metal toxicity, modulate phenylpropanoid metabolism and trigger the accumulation of specific polyphenolic compounds. The antioxidant properties of these metabolites, including phenolic acids, flavonoids, anthocyanins, lignin, and polyphenols, and their roles in reactive oxygen species scavenging, neutralizing free radicals, membrane stabilization, and osmotic adjustment are discussed. Understanding these mechanisms and metabolic responses is crucial for developing stress-resilient crops and improving agricultural productivity under increasingly challenging environmental conditions. This review provides comprehensive insights into integrating phenylpropanoid metabolism with plant stress adaptation mechanisms, highlighting potential targets for enhancing crop stress tolerance through metabolic adjustment.

Fusarium head blight (FHB) threatens global wheat (Triticum aestivum L.) production and food security. Fhb1 confers stable, broad-spectrum resistance to FHB, but the underlying molecular mechanisms are not fully understood. In this study, integrated transcriptomic and proteomic analyses of near-isogenic lines for the Fhb1 locus revealed that Fhb1 coordinates a multi-layered defense network characterized by extensive transcriptome reprogramming and post-transcriptional regulation. The phenylpropanoid pathway emerged as a central downstream module, as Fhb1 coordinately upregulates the expression of genes encoding key enzymes in this pathway, including PHENYLALANINE AMMONIA LYASE (PAL), CINNAMATE 4-HYDROXYLASE (C4H), and 4-COUMARATE-CoA LIGASE (4CL). Gene regulatory network analysis identified the R2R3-MYB transcription factor TaMYB30-B1 as a key regulatory hub. A single nucleotide polymorphism (SNP) in TaMYB30-B1 was significantly associated with FHB resistance across natural wheat populations. This association was more pronounced in the absence of Fhb1. Our findings elucidate the mechanistic basis for Fhb1-mediated resistance and highlight TaMYB30-B1 as a valuable target for improving FHB resistance in wheat breeding programs.

Biotic stresses, particularly Verticillium wilt (VW), lead to a global decline in cotton yields. Here, we demonstrate that ectopic expression of ScALDH21, a gene from the desiccation-tolerant moss Syntrichia caninervis Mitt. and absent in angiosperms, enhances cotton's resistance to VW. Multi-year, multiple location field evaluations showed that transgenic cotton lines consistently exhibited two major advantages: markedly improved resistance to VW, and significantly reduced yield loss, with an approximate 23.8% yield increase relative to non-transgenic counterparts under pathogen infection conditions. This disease resistance is associated with enhanced capacity of the transgenic lines to scavenge reactive oxygen species (ROS), induced by pathogen infection. This finding aligns with the ScALDH21-conferred detoxification function. Transcriptome analyses revealed a significant alteration in expression pattern of those genes that regulate phenylpropanoid and jasmonic acid (JA) pathways. Correspondingly, the accumulation of lignin and defence-related metabolites (e.g., rutin, cyanidin and jasmonates) significantly increased, suggesting that ScALDH21-mediated activation of the phenylpropanoid and JA pathways contributes to enhanced resistance. Analyses of ScALDH21 binding activity using CUT&Tag and EMSA assays showed that it can bind to specific gene promoters within the cotton genome, highlighting that ScALDH21 not only catalyses the detoxification of aldehydes but also gains transcriptional regulatory roles. In summary, we demonstrate that expression of the heterologous ScALDH21 in cotton leads to enhancement of resistance to VW and elucidated the mechanism. Our findings further demonstrate a promising strategy to improve biotic resistance in crops by utilizing unique functional genes from evolutionarily distant species in extreme environments.