CYP77A19 and CYP77A20 characterized from Solanum tuberosum oxidize fatty acids in vitro and partially restore the wild phenotype in an Arabidopsis thaliana cutin mutant

Nitrile biosynthesis in nature: how and why?

Covering: up to the end of 2023Natural nitriles comprise a small set of secondary metabolites which however show intriguing chemical and functional diversity. Various patterns of nitrile biosynthesis can be seen in animals, plants, and microorganisms with the characteristics of both evolutionary divergence and convergence. These specialized compounds play important roles in nitrogen metabolism, chemical defense against herbivores, predators and pathogens, and inter- and/or intraspecies communications. Here we review the naturally occurring nitrile-forming pathways from a biochemical perspective and discuss the biological and ecological functions conferred by diversified nitrile biosyntheses in different organisms. Elucidation of the mechanisms and evolutionary trajectories of nitrile biosynthesis underpins better understandings of nitrile-related biology, chemistry, and ecology and will ultimately benefit the development of desirable nitrile-forming biocatalysts for practical applications.

Site-Directed Mutagenesis of VvCYP76F14 (Cytochrome P450) Unveils Its Potential for Selection in Wine Grape Varieties Linked to the Development of Wine Bouquet

Bouquet is a fascinating wine characteristic that serves as an indicator of wine quality, developing during the aging process. The multifunctional monoterpenol oxidase VvCYP76F14 in wine grapes sequentially catalyzes three reactions to produce (E)-8-carboxylinalool, a crucial precursor for wine bouquet. Previous studies indicated that the activity of VvCYP76F14 derived from different wine grape varieties did not correlate with the amino acid sequence differences. In this study, 54 wine grape varieties were categorized into neutral, aromatic, and full-bodied types based on the sequence differences of VvCYP76F14, closely correlated with the content of wine lactone precursors. Computer modeling and molecular docking analysis of the full-bodied CYP76F14 revealed 17, 19, and 18 amino acid residues in the VvCYP76F14-linalool, VvCYP76F14-(E)-8-hydroxylinalool, and VvCYP76F14-(E)-8-oxolinalool complexes, respectively. Site-directed mutagenesis and in vitro enzyme activity analysis confirmed the substitutions of the key amino acid residues in neutral and aromatic varieties. Notably, the D299 mutation of VvCYP76F14 resulted in the complete loss of (E)-8-oxolinalool and (E)-8-carboxylinalool activities, aligning with the undetectable levels of (E)-8-oxolinalool and (E)-8-carboxylinalool in "Yantai 2-3-37", which harbors the D299T substitution. Favorably, VvCYP76F14 could serve as a cost-effective fingerprint marker for screening superior hybrid offspring with the desired levels of wine lactone precursors.

Engineering of CYP82Y1, a cytochrome P450 monooxygenase: a key enzyme in noscapine biosynthesis in opium poppy

Protein engineering provides a powerful base for the circumvention of challenges tied with characteristics accountable for enzyme functions. CYP82Y1 introduces a hydroxyl group (-OH) into C1 of N-methylcanadine as the substrate to yield 1-hydroxy-N-methylcanadine. This chemical process has been found to be the gateway to noscapine biosynthesis. Owning to the importance of CYP82Y1 in this biosynthetic pathway, it has been selected as a target for enzyme engineering. The insertion of tags to the N- and C-terminal of CYP82Y1 was assessed for their efficiencies for improvement of the physiological performances of CYP82Y1. Although these attempts achieved some positive results, further strategies are required to dramatically enhance the CYP82Y1 activity. Here methods that have been adopted to achieve a functionally improved CYP82Y1 will be reviewed. In addition, the possibility of recruitment of other techniques having not yet been implemented in CYP82Y1 engineering, including the substitution of the residues located in the substrate recognition site, formation of the synthetic fusion proteins, and construction of the artificial lipid-based scaffold will be discussed. Given the fact that the pace of noscapine synthesis is constrained by the CYP82Y1-catalyzing step, the methods proposed here are capable of accelerating the rate of reaction performed by CYP82Y1 through improving its properties, resulting in the enhancement of noscapine accumulation.

Identification and characterization of cytochrome P450 CYP77A59 of loquat (Rhaphiolepis bibas) responsible for biosynthesis of phenylacetonitrile, a floral nitrile compound

MAIN CONCLUSION

Cytochrome P450 CYP77A59 is responsible for the biosynthesis of phenylacetonitrile in loquat flowers. Flowers of some plants emit volatile nitrile compounds, but the biosynthesis of these compounds is unclear. Loquat (Rhaphiolepis bibas) flowers emit characteristic N-containing volatiles, such as phenylacetonitrile (PAN), (E/Z)-phenylacetaldoxime (PAOx), and (2-nitroethyl)benzene (NEB). These volatiles likely play a defense role against pathogens and insects. PAN and NEB are commonly biosynthesized from L-phenylalanine via (E/Z)-PAOx. Two cytochrome P450s-CYP79D80 and "promiscuous fatty acid ω-hydroxylase" CYP94A90, which catalyze the formation of (E/Z)-PAOx from L-phenylalanine and NEB from (E/Z)-PAOx, respectively-are involved in NEB biosynthesis. However, the enzymes catalyzing the formation of PAN from (E/Z)-PAOx in loquat have not been identified. In this study, we aimed to identify candidate cytochrome P450s catalyzing PAN formation in loquat flowers. Yeast whole-cell biocatalyst assays showed that among nine candidate cytochrome P450s, CYP77A58 and CYP77A59 produced PAN from (E/Z)-PAOx. CYP77As catalyzed the dehydration of aldoximes, which is atypical of cytochrome P450; the reaction was NADPH-dependent, with an optimum temperature and pH of 40 °C and 8.0, respectively. CYP77As acted on (E/Z)-PAOx, (E/Z)-4-hydroxyphenylacetaldoxime, and (E/Z)-indole-3-acetaldoxime. Previously characterized CYP77As are known to hydroxylate fatty acids; loquat CYP77As did not act on tested fatty acids. We observed higher expression of CYP77A59 in flowers than in buds; expression of CYP77A58 was remarkably reduced in the flowers. Because the flowers, but not buds, emit PAN, CYP77A59 is likely responsible for the biosynthesis of PAN in loquat flowers. This study will help us understand the biosynthesis of floral nitrile compounds.

Role of Cytochrome P450 Enzyme in Plant Microorganisms' Communication: A Focus on Grapevine

Cytochromes P450 are ancient enzymes diffused in organisms belonging to all kingdoms of life, including viruses, with the largest number of P450 genes found in plants. The functional characterization of cytochromes P450 has been extensively investigated in mammals, where these enzymes are involved in the metabolism of drugs and in the detoxification of pollutants and toxic chemicals. The aim of this work is to present an overview of the often disregarded role of the cytochrome P450 enzymes in mediating the interaction between plants and microorganisms. Quite recently, several research groups have started to investigate the role of P450 enzymes in the interactions between plants and (micro)organisms, focusing on the holobiont Vitis vinifera. Grapevines live in close association with large numbers of microorganisms and interact with each other, regulating several vine physiological functions, from biotic and abiotic stress tolerance to fruit quality at harvest.

Characterization of the Oxylipin Pattern and Other Fatty Acid Oxidation Products in Freshly Pressed and Stored Plant Oils

Enzymatic and nonenzymatic oxidation of linoleic (LA) and α-linolenic acid (ALA) during pressing and storage of plant oils leads to a variety of oxylipins. We pressed oils from flaxseeds, rapeseeds, and sunflower seeds and analyzed the oxylipin pattern in freshly pressed oils. 9-/13-Hydro(pero)xy-LA/-ALA occurred in high concentration resulting probably from lipoxygenase-catalyzed reactions as well as autoxidation and photooxidation. However, in flaxseed and rapeseed oil, the highest concentrations were found for the terminal epoxy-ALA (15(16)-EpODE) and the hardly known 15-hydroxy-LA (15-HODE, 80 mg/100 g in flaxseed oil). Oils were stored for 6 months and the peroxide value (PV) as well as oxylipin and secondary volatile aldehyde concentrations were determined. While lipid peroxidation in flaxseed oil was surprisingly low, the oxylipin concentration and PV massively increased in rapeseed oil dependent on oxygen availability. Oxylipin concentrations correlated well with the PV, while secondary volatile aldehydes did not reflect the changes of oxylipins and PVs. The comprehensive analysis of hydroxy-, epoxy-, and dihydroxy-LA/-ALA reveals new and unique insights into the composition of plant oils and ongoing oxidation processes.

Genome-wide transcriptome analysis and characterization of the cytochrome P450 flavonoid biosynthesis genes in pigeon pea (Cajanus cajan)

226 CcCYP450 genes were identified at the genomic level and were classified into 45 clades based on phylogenetic analysis. CcCYP75B165 gene was found that might play important roles in the biosynthesis of flavonoids in pigeon pea, and was significantly induced by methyl jasmonate (MeJA). The cytochrome P450 mono-oxygenase (CYP450) superfamily plays a key role in the flavonoid biosynthesis pathway and resists different kinds of stresses. Several CYP450 genes have been identified to be involved in the biosynthesis of crop protection agents. However, the CcCYP450 genes from pigeon pea have not been identified. Here, 226 CcCYP450 genes were identified at the genomic level by analysing the gene structure, distribution on chromosomes, gene duplication, and conserved motifs and were classified into 45 clades based on phylogenetic analysis. RNA-seq analysis revealed clear details of CcCYP450 genes that varied with time of MeJA (methyl jasmonate) induction. Among them, six CcCYP450 subfamily genes were found that might play important roles in the biosynthesis of flavonoids in pigeon pea. The overexpression of CcCYP75B165 in pigeon pea significantly induced the accumulation of genistin and downregulated the contents of cajaninstilbene acid, apigenin, isovitexin, and genistein and the expression of flavonoid synthase genes. This study provides theoretical guidance and plant genetic resources for cultivating new pigeon pea varieties with high flavonoid contents and exploring the molecular mechanisms of the biosynthesis of flavonoids under MeJA treatment.

Molecular Biology, Composition and Physiological Functions of Cuticle Lipids in Fleshy Fruits

Fleshy fruits represent a valuable resource of economic and nutritional relevance for humanity. The plant cuticle is the external lipid layer covering the nonwoody aerial organs of land plants, and it is the first contact between fruits and the environment. It has been hypothesized that the cuticle plays a role in the development, ripening, quality, resistance to pathogen attack and postharvest shelf life of fleshy fruits. The cuticle's structure and composition change in response to the fruit's developmental stage, fruit physiology and different postharvest treatments. This review summarizes current information on the physiology and molecular mechanism of cuticle biosynthesis and composition changes during the development, ripening and postharvest stages of fleshy fruits. A discussion and analysis of studies regarding the relationship between cuticle composition, water loss reduction and maintaining fleshy fruits' postharvest quality are presented. An overview of the molecular mechanism of cuticle biosynthesis and efforts to elucidate it in fleshy fruits is included. Enhancing our knowledge about cuticle biosynthesis mechanisms and identifying specific transcripts, proteins and lipids related to quality traits in fleshy fruits could contribute to the design of biotechnological strategies to improve the quality and postharvest shelf life of these important fruit crops.

CYP77B1 a fatty acid epoxygenase specific to flowering plants

Contrary to animals, little is known in plants about enzymes able to produce fatty acid epoxides. In our attempt to find and characterize a new fatty acid epoxygenase in Arabidopsis thaliana, data mining brought our attention on CYP77B1. Modification of the N-terminus was necessary to get enzymatic activity after heterologous expression in yeast. The common plant fatty acid C18:2 was converted into the diol 12,13-dihydroxy-octadec-cis-9-enoic acid when incubated with microsomes of yeast expressing modified CYP77B1 and AtEH1, a soluble epoxide hydrolase. This diol originated from the hydrolysis by AtEH1 of the epoxide 12,13-epoxy-octadec-cis-9-enoic acid produced by CYP77B1. A spatio-temporal study of CYP77B1 expression performed with RT-qPCR revealed the highest level of transcripts in flower bud while, in open flower, the enzyme was mainly present in pistil. CYP77B1 promoter-driven GUS expression confirmed reporter activities in pistil and also in stamens and petals. In silico co-regulation data led us to hypothesize that CYP77B1 could be involved in cutin synthesis but when flower cutin of loss-of-function mutants cyp77b1 was analyzed, no difference was found compared to cutin of wild type plants. Phylogenetic analysis showed that CYP77B1 is strictly conserved in flowering plants, suggesting a specific function in this lineage.

Lipidomic Analysis of Oxidized Fatty Acids in Plant and Algae Oils

Linoleic acid (LA) and α-linolenic acid (ALA) in plant or algae oils are precursors to oxidized fatty acid metabolites known as oxylipins. Liquid chromatography tandem mass spectrometry was used to quantify oxylipins in soybean, corn, olive, canola, and four high-oleic acid algae oils at room temperature or after heating for 10 min at 100 °C. Flaxseed oil oxylipin concentrations were determined in a follow-up experiment that compared it to soybean, canola, corn, and olive oil. Published consumption data for soybean, canola, corn, and olive oil were used to estimate daily oxylipin intake. The LA and ALA fatty acid composition of the oils was generally related to their respective oxylipin metabolites, except for olive and flaxseed oil, which had higher LA derived monohydroxy and ketone oxylipins than other oils, despite their low LA content. Algae oils had the least amount of oxylipins. The change in oxylipin concentrations was not significantly different among the oils after short-term heating. The estimated oxylipin intake from nonheated soybean, canola, corn, and olive oil was 1.1 mg per person per day. These findings suggest that oils represent a dietary source of LA and ALA derived oxylipins and that the response of oils to short-term heating does not differ among the various oils.

Modification of olefinic double bonds of unsaturated fatty acids and other vegetable oil derivatives via epoxidation: A review

The highly strained ring in epoxides makes these compounds very versatile intermediates. Epoxidized vegetable oils are gaining a lot of attention as renewable and environmentally friendly feedstock with various industrial applications such as plasticizers, lubricant base oils, surfactants, etc. Numerous papers have been published on the development of the epoxidation methods and the number is still growing. This review reports the synthetic approaches and applications of epoxidized vegetable oils.

WAX INDUCER1 (HvWIN1) transcription factor regulates free fatty acid biosynthetic genes to reinforce cuticle to resist Fusarium head blight in barley spikelets

Fusarium head blight (FHB), caused by Fusarium graminearum, is one of the most devastating diseases of wheat and barley. Resistance to FHB is highly complex and quantitative in nature, and is most often classified as resistance to spikelet infection and resistance to spread of pathogen through the rachis. In the present study, a resistant (CI9831) and a susceptible (H106-371) two-row barley genotypes, with contrasting levels of spikelet resistance to FHB, pathogen or mock-inoculated, were profiled for metabolites based on liquid chromatography and high resolution mass spectrometry. The key resistance-related (RR) metabolites belonging to fatty acids, phenylpropanoids, flavonoids and terpenoid biosynthetic pathways were identified. The free fatty acids (FFAs) linoleic and palmitic acids were among the highest fold change RR induced (RRI) metabolites. These FFAs are deposited as cutin monomers and oligomers to reinforce the cuticle, which acts as a barrier to pathogen entry. Quantitative real-time PCR studies revealed higher expressions of KAS2, CYP86A2, CYP89A2, LACS2 and WAX INDUCER1 (HvWIN1) transcription factor in the pathogen-inoculated resistant genotype than in the susceptible genotype. Knockdown of HvWIN1 by virus-induced genes silencing (VIGS) in resistant genotype upon pathogen inoculation increased the disease severity and fungal biomass, and decreased the abundance of FFAs like linoleic and palmitic acids. Notably, the expression of CYP86A2, CYP89A2 and LAC2 genes was also suppressed, proving the link of HvWIN1 in regulating these genes in cuticle biosynthesis as a defense response.

Comparative transcriptome and proteome analysis to reveal the biosynthesis of gold nanoparticles in Arabidopsis

A large number of plants have been tested and exploited in search of a green chemistry approach for the fabrication of gold or other precious metal nanomaterials. Despite the potential of plant based methods, very little is known about the underlying biochemical reactions and genes involved in the biotransformation mechanism of AuCl₄ into gold nanoparticles (AuNPs). In this research, we thus focused on studying the effect of Au on growth and nanoparticles formation by analyses of transcriptome, proteome and ionome shift in Arabidopsis. Au exposure favored the growth of Arabidopsis seedling and induced formation of nanoparticles in root and shoot, as indicated by optical and hyperspectral imaging. Root transcriptome analysis demonstrated the differential expression of the members of WRKY, MYB and BHLH gene families, which are involved in the Fe and other essential metals homeostasis. The proteome analysis revealed that Glutathione S-transferases were induced in the shoot and suggested its potential role in the biosynthesis AuNPs. This study also demonstrated the role of plant hormone auxin in determining the Au induced root system architecture. This is the first study using an integrated approach to understand the in planta biotransformation of KAuCl₄ into AuNPs.

Stress memory induced rearrangements of HSP transcription, photosystem II photochemistry and metabolism of tall fescue (Festuca arundinacea Schreb.) in response to high-temperature stress

When plants are pre-exposed to stress, they can produce some stable signals and physiological reactions that may be carried forward as "stress memory". However, there is insufficient information about plants' stress memory responses mechanisms. Here, two tall fescue genotypes, heat-tolerant PI 574522 and heat-sensitive PI 512315, were subjected to recurring high-temperature pre-acclimation treatment. Two heat shock protein (HSP) genes, LMW-HSP and HMW-HSP, exhibited transcriptional memory for their higher transcript abundance during one or more subsequent stresses (S2, S3, S4) relative to the first stress (S1), and basal transcript levels during the recovery states (R1, R2, and R3). Activated transcriptional memory from two trainable genes could persist up to 4 days, and induce higher thermotolerance in tall fescue. This was confirmed by greater turf quality and lower electrolyte leakage. Pre-acclimation treatment inhibited the decline at steps of O-J-I-P and energy transport fluxes in active Photosystem II reaction center (PSII RC) for both tall fescue genotypes. The heat stress memory was associated with major shifts in leaf metabolite profiles. Furthermore, there was an exclusive increase in leaf organic acids (citric acid, malic acid, tris phosphoric acid, threonic acid), sugars (sucrose, glucose, idose, allose, talose, glucoheptose, tagatose, psicose), amino acids (serine, proline, pyroglutamic acid, glycine, alanine), and one fatty acid (butanoic acid) in pre-acclimated plants. These observations involved in transcriptional memory, PSII RC energy transport and metabolite profiles could provide new insights into the plant high-temperature response process.