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Abstract Salicylic acid (SA) is a central regulator of plant immunity, and precise control of its levels is essential to balance defense and growth. However, the mechanisms controlling the stability and abundance of SA-catabolizing enzymes remain elusive. Here we show that the SA hydroxylases DOWNY MILDEW RESISTANT 6 (DMR6) and DMR6-LIKE OXYGENASE 1 (DLO1) are targeted for ubiquitin–proteasome-dependent degradation. SA promotes DMR6 turnover but stabilizes DLO1, linking catalytic activity and conformational dynamics to protein fate. Structural and biochemical analyses indicate that SA binding induces conformational changes in DMR6, particularly in a conserved C-terminal helix, which may contribute to its susceptibility to degradation. Proximity labeling of DMR6 and DLO1 identified a previously uncharacterized Kelch-type F-box protein, which we designate as DMR6-ASSOCIATED F-BOX 1 (DAF1), that contributes to SCF-type E3 ligase-mediated proteasomal turnover of DMR6 in planta, thereby modulating SA-mediated cell death. Complementary proximity labeling of the SCF adaptor ASK1 in Arabidopsis duringPseudomonas syringaeinfection uncovered remodeling of F-box networks while consistently recovering DMR6 and DLO1, highlighting their integration within immune-responsive proteolytic circuits. These findings support a self-limiting regulatory circuit in which SA simultaneously induces and destabilizes its catabolic enzymes, coupling hormone metabolism with proteasome-mediated control of immune homeostasis. 

Abstract Plant agriculture contributes substantially to global greenhouse gas emissions, yet it also offers powerful opportunities for climate change mitigation. Here, we focus on how to identify and prioritize synthetic biology strategies to reduce emissions and sequester carbon through plant-based interventions. Effective solutions must process large volumes of carbon, be scalable, yield a positive life-cycle balance, and be economically viable, technically feasible, and deployable in field conditions without undue damage to what remains of nature on Earth. Using Fermi estimation, we quantify the per-hectare, annual, and 100-year CO2-equivalent (CO2e) drawdown potential of emerging synthetic biology strategies—including improved CO2 fixation, reduced yield losses, root-deposited biopolymers, engineered nitrogen fixation, and methane reduction—and benchmark them against nonengineered approaches such as biochar, forestation, and fast-growing biomass crops. We used a 100-year horizon to allow for both development and implementation of high-risk but high-impact synthetic biology strategies. We integrate factors such as per-hectare effectiveness, year-on-year sequestration, deployment area, and storage durability. We demonstrate that while per-hectare impacts vary by orders of magnitude (<1 to >30 t CO2e/ha/year), deployment scale is the dominant factor determining total impact. Targeted synthetic biology strategies implemented across existing agricultural systems could deliver ∼120 Gt CO2e drawdown over a century and contribute to an additional ∼140 Gt CO2e drawdown. Decreasing synthetic nitrogen fertilizer use and biochar implementation have the biggest CO2e impact potential. Early-stage quantitative evaluation is critical to guide R&D toward climate-relevant solutions and deliver a prioritized portfolio of near- and long-term strategies. A transdisciplinary approach—linking synthetic biology, agronomy, engineering, and social systems—is essential to realize impact. This work offers a framework for evaluating plant agriculture-based climate mitigation strategies and highlights a key role for synthetic biology in mitigation pathways. Regular re-evaluation of strategies should be performed to ensure that they are meaningful for climate change mitigation as other factors evolve. 

Abstract Strawberry (Fragaria × ananassa) is a globally cultivated fruit crop appreciated by consumers for its unique flavor and aroma. Major groups of volatile organic compounds that define strawberry aroma include terpenes, fatty acid esters, furanones, and benzenoids, with complex terpene blends contributing characteristic fruity, citrus, and floral notes. Here, we report the genome-wide identification and functional analysis of the terpene synthase (TPS) family that governs terpene chemical diversity in strawberry. Mining of the allo-octoploid genome of the commercial “Royal Royce” cultivar identified 75 TPS gene candidates. Biochemical characterization of 33 mono-, sesqui- and di-TPS enzymes via recombinant protein assays and/or microbial co-expression studies demonstrated TPS activities involved in the biosynthesis of nearly two-thirds of known strawberry terpenes as well as products not previously described in octoploid strawberry. Complementary metabolomic and transcriptomic studies across a diversity panel of strawberry accessions illustrated substantial variation in the composition and abundance of more than 30 common and accession-specific terpene aroma metabolites. Analysis of 2 commercial accessions, “Royal Royce” and “Mara de Bois,” with contrasting aroma profiles further revealed accession-specific alterations of terpene metabolism during fruit ripening. These findings expand our understanding of the biosynthetic genes and pathways underlying strawberry terpene metabolism and provide resources to develop breeding strategies toward improving desirable strawberry aroma traits. 

Real Christmas trees contribute ~$2.5 billion to the US economy annually. True fir (Abies spp.) are the most popular trees and account for the majority of sales. The real Christmas tree commodity board identified aroma as the primary driver for consumers to purchase a real tree. We conducted consumer aroma panels for five (Fraser, noble, Nordmann, Trojan, and concolor) of the most popular fir Christmas trees in the US. Based on aroma characteristics alone, Fraser fir was found to be most liked while noble fir ranked last amongst consumers. Gas Chromatography Mass Spectroscopy metabolite profiling of terpene (the major drivers of conifer aroma) putatively identified 132 mono- and sesquiterpene and 48 diterpene metabolites across all five species. Among these, the sesquiterpene, β-bisabolene, was strongly correlated with consumer liking. These findings provide a resource to identify compounds positively associated with consumer preference to help guide Christmas tree genetic improvement efforts. 

Abstract The Plant Metabolic Network (PMN) is a free online database of plant metabolism available at https://plantcyc.org. The latest release, PMN 16, provides metabolic databases representing >1200 metabolic pathways, 1.3 million enzymes, >8000 metabolites, >10 000 reactions and >15 000 citations for 155 plant and green algal genomes, as well as a pan-plant reference database called PlantCyc. This release contains 29 additional genomes compared with PMN 15, including species listed by the African Orphan Crop Consortium and nonflowering plant species. Furthermore, 52 new enzymes with experimentally supported function information have been included in this release. The single-species databases contain a combination of experimental information from the literature and computationally predicted information obtained through PMN’s database generation pipeline for a single species, while PlantCyc contains only experimental information but for any species within Viridiplantae. PMN is a comprehensive resource for querying, visualizing, analyzing and interpreting omics data with metabolic knowledge. It also serves as a useful and interactive tool for teaching plant metabolism. 

Abstract The diversity of plant natural products presents a rich resource for accelerating drug discovery and addressing pressing human health issues. However, the challenges in accessing and cultivating source species, as well as metabolite structural complexity, and general low abundance present considerable hurdles in developing plant-derived therapeutics. Advances in high-throughput sequencing, genome assembly, gene synthesis, analytical technologies, and synthetic biology approaches, now enable us to efficiently identify and engineer enzymes and metabolic pathways for producing natural and new-to-nature therapeutics and drug candidates. This review highlights challenges and progress in plant natural product discovery and engineering by example of recent breakthroughs in identifying the missing enzymes involved in the biosynthesis of the anti-cancer agent Taxol^®. These enzyme resources offer new avenues for the bio-manufacture and semi-synthesis of an old blockbuster drug. 

Summary Diverse networks of specialized metabolites promote plant fitness by mediating beneficial and antagonistic environmental interactions. In maize (Zea mays), constitutive and dynamically formed cocktails of terpenoids, benzoxazinoids, oxylipins, and phenylpropanoids contribute to plant defense and ecological adaptation. Recent research has highlighted the multifunctional nature of many specialized metabolites, serving not only as elaborate chemical defenses that safeguard against biotic and abiotic stress but also as regulators in adaptive developmental processes and microbiome interactions. Great strides have also been made in identifying the modular pathway networks that drive maize chemical diversity. Translating this knowledge into strategies for enhancing stress resilience traits has the potential to address climate‐driven yield losses in one of the world's major food, feed, and bioenergy crops. 

Abstract The evolutionary expansion of specialized metabolism has shaped the ability of plants to adapt to combined pathogen, pest, and other environmental pressures. For instance, the duplication and divergence of ancestral gibberellin pathway genes have given rise to specialized kauralexin and dolabralexin diterpenoids in maize (Zea mays) that serve as core components of disease resistance and stress adaptation. Here, we describe the biosynthesis and elicited production of rosalexins as a previously unrecognized component of the maize chemical defense network. By integrating genomics-enabled gene discovery, combinatorial enzyme assays, and AI-assisted enzyme mechanistic studies we show that maize rosalexin biosynthesis proceeds via a distinct 5-rosanol scaffold formed by the pairwise activity of two diterpene synthases, ZmTPS38/CPS2/AN2 and ZmTPS42/KSL1, recruited from gibberellin metabolism. Further oxygenation by the promiscuous P450 enzyme, ZmCYP71Z18, yields epoxyrosanol that, in turn, can undergo epoxide ring opening to form trihydroxyrosanol. Epoxyrosanol, but not 5-rosanol or trihydroxyrosanol, display strong inhibitory activity on fungal pathogen growthin vitro, highlighting the contribution of the epoxide group to antibiotic efficacy. Large variation in rosalexin presence and abundance exists across maize genotypes due to expansiveZmTPS42/KSL1gene sequence variation and pseudogenization. Transcriptomics and targeted metabolomics demonstrated the pathogen-elicited accumulation of rosalexins in maize lines featuring functionalZmTPS42/KSL1genes. However, no dominant pathogen resistance phenotype was observed in association with rosalexin abundance. These collective findings expand our knowledge of how multiple interconnected diterpenoid pathways arose in maize via duplication of hormone-metabolic genes and enable the utilization of a common precursor to form modular chemical defense layers. Significance StatementPlant diterpenoids play critical roles in crop development, stress defense and ecological adaptation. In maize, diterpenoids serve as key components of chemical defenses against pests and diseases with direct impact on crop immunity and vigor. Enzymes of the diterpene synthase and cytochrome P450 families largely drive diterpenoid chemical diversity. This study reports the discovery and characterization of the pathway forming rosalexin diterpenoids in maize. Pathogen-elicited accumulation and in vitro antifungal activity of rosalexin metabolites supports a physiological function in maize chemical defense. 

Abstract Plants deploy both primary and species-specific, specialized metabolites to communicate with other organisms and adapt to environmental challenges, including interactions with soil-dwelling microbial communities. However, the role of specialized metabolites in modulating plant-microbiome interactions often remains elusive. In this study, we report that maize ( Zea mays ) diterpenoid metabolites with known antifungal bioactivities also influence rhizosphere bacterial communities. Metabolite profiling showed that dolabralexins, antibiotic diterpenoids that are highly abundant in roots of some maize varieties, can be exuded from the roots. Comparative 16S rRNA gene sequencing determined the bacterial community composition of the maize mutant Zman2 ( anther ear 2 ), which is deficient in dolabralexins and closely related bioactive kauralexin diterpenoids. The Zman2 rhizosphere microbiome differed significantly from the wild-type sibling with the most significant changes observed for Alphaproteobacteria of the order Sphingomonadales. Metabolomics analyses support that these differences are attributed to the diterpenoid deficiency of the Zman2 mutant, rather than other large-scale metabolome alterations. Together, these findings support physiological functions of maize diterpenoids beyond known chemical defenses, including the assembly of the rhizosphere microbiome. 

The cereal scutellum is a hub for diverse specialized defense metabolism and pathway discovery.