Biodiversity is adversely affected by the growing levels of synthetic chemicals released into the environment due to agricultural activities. This has been the driving force for embracing sustainable agriculture. Plant secondary metabolites offer promising alternatives for protecting plants against microbes, feeding herbivores, and weeds. Terpenes are the largest among PSMs and have been extensively studied for their potential as antimicrobial, insecticidal, and weed control agents. They also attract natural enemies of pests and beneficial insects, such as pollinators and dispersers. However, most of these research findings are shelved and fail to pass beyond the laboratory and greenhouse stages. This review provides an overview of terpenes, types, biosynthesis, and their roles in protecting plants against microbial pathogens, insect pests, and weeds to rekindle the debate on using terpenes for the development of environmentally friendly biopesticides and herbicides.

The phenylpropanoid pathway remains a key target for most climate-resilient crop development, owing to it being a precursor to over 8000 metabolites, including flavonoids and lignin compounds, including their derivatives. These metabolites are involved in biotic and abiotic stress tolerance, inviting several studies into their roles in plant defense, drought, temperature, UV, and nutrient stress tolerance. Literature is currently inundated with cutting-edge reports on the phenylpropanoid pathways and their functions. Here, we provide a comprehensive update on the biosynthesis of phenylpropanoids, mainly lignin and flavonoids, their roles in biotic and abiotic interaction, and transcending topics, including pest and diseases, drought, temperature, and UV stress tolerance. We further reviewed the post-transcriptional, post-translational, and epigenetic modifications regulating phenylpropanoid metabolism and highlighted their applications and optimization strategies for large-scale production. This review provides an all-inclusive update on recent reports on the metabolism of phenylpropanoids in plants.

Fungi infections cause approximately 60–70% yield loss through diseases such as rice blast, powdery mildew, Fusarium rot, downy mildew, etc. Plants naturally respond to these infections by eliciting an array of protective metabolites to confer physical or chemical protection. Among plant metabolites, lignin, a phenolic compound, thickens the middle lamella and the secondary cell walls of plants to curtail fungi infection. The biosynthesis of monolignols (lignin monomers) is regulated by genes whose transcript abundance significantly improves plant defense against fungi. The catalytic activities of lignin biosynthetic enzymes also contribute to the accumulation of other defense compounds. Recent advances focus on modifying the lignin pathway to enhance plant growth and defense against pathogens. This review presents an overview of monolignol regulatory genes and their contributions to fungi immunity, as reported over the last five years. This review expands the frontiers in lignin pathway engineering to enhance plant defense.

Societal Impact Statement: Gossypol and its derivatives represent a class of toxic and immunosuppressive compounds that are naturally synthesized in cottonseed. These compounds pose several health hazards to humans and animals, such as heart and lung damage, breathing difficulties, and death in swine. In poultry, gossypol reduces egg production and slows growth. Studies have also shown that gossypol can indirectly harm humans and animals through the food chain. Although several physical and chemical approaches are adopted to reduce gossypol levels in cottonseed before food and feed processing, these techniques are expensive. Therefore, genetically regulating gossypol production in cotton could provide a cheaper alternative.Summary: Cotton (Gossypium spp.), the most important fiber crop, is cultivated in over a hundred countries to provide raw materials for the growing textile industry. The seed obtained after delinting cotton is a rich source of protein with a vast potential for oil and feed production. Cottonseed oil production is estimated at 5.08 million metric tons and is expected to generate over 6.56 billion United States Dollars in revenue by 2029. The cake from defatted cottonseed is used as animal feed and food supplements. However, the contamination of gossypol in cottonseed limits its use. Gossypol ingestion impairs weight gain and causes anorexia, respiratory distress, and death under extreme exposure. This review highlights the significance of cottonseed oil and meal; the pharmacological uses and impact of gossypol; the chemistry, toxicity, and bioactivity of gossypol; and the physical and chemical methods used in gossypol removal during feed and food supplement processing. In addition, the biosynthetic pathway of gossypol and attempts to genetically transform some key regulators of this pathway to produce glandless cottonseed or reduce the gossypol levels in the seed are discussed.

Cassava (Manihot esculenta) is a vital tropical staple crop with expanding relevance beyond food security, particularly in developing functional beverages and nutraceutical products. This review discusses the implications of selected chemicals in cassava roots for beverage production, notably cyanogenic glycosides and phenolic compounds. We further highlight the role of cassava as a substrate for beverage production, the nutritional significance of cassava-based beverages, and the health benefits and functional potential of cassava as a key ingredient in beverage production. We also discuss the probiotic and prebiotic properties and the antioxidant activity of chemicals in cassava-based beverages for health benefits. Additionally, we review the challenges, opportunities, and innovations regarding commercialization.