Catalysis by allene oxide synthases (CYP74A and CYP74C): Alterations by the Phe/Leu mutation at the SRS-1 region

Alterations of asparagus (Asparagus officinalis L.) divinyl ether synthase (CYP74H2) catalysis by site-directed mutagenesis

Divinyl ether synthases (DESs) are the enzymes catalyzing the dehydration of fatty acid hydroperoxides to divinyl ether oxylipins. DESs, along with allene oxide synthases (AOSs), hydroperoxide lyases (HPLs), and epoxyalcohol synthases (EASs), are members of the CYP74 clan of unusual cytochromes P450 playing a key role in the lipoxygenase pathway. The present work focuses on the study of the structure-function relationships in Asparagus officinalis DES (AoDES, CYP74H2) via site-directed mutagenesis at some catalytically essential sites. Single mutant forms L106F and L282G retained the DES activity. However, the L106F mutant possessed significant alteration of stereochemical specificity of divinyl ether synthesis compared with WT AoDES. For example, while WT AoDES specifically converted linoleic acid 13(S)-hydroperoxide into (11Z)-etheroleic acid, its yield was significantly reduced by the L106F mutation, whereas etheroleic and (all-E)-etheroleic acids were the major ones. In contrast, the L282G mutation did not significantly affect the (11Z)-etheroleic acid formation. However, the L282G protein produced some additional products like those of HPL and EAS, along with divinyl ethers. The L106F/L282G double mutant protein lost DES activity. It converted α-linolenic 9- and 13-hydroperoxides into HPL chain cleavage products. At the same time, this mutant efficiently converted the linoleic acid 9-hydroperoxide into diol, 9,14-dihydroxy-10,12-octadecadienoic acid, presumably via the hydrolysis of the short-lived epoxydiene, 9,10-epoxy-11,13-octadecadienoic acid. Furthermore, the L106F/L282G/Q343P triple mutant showed AOS activity alongside DES. The appearance of EAS and HPL catalysis, as well as the biosynthesis of 9,14-epoxydiene via short-lived epoxydiene via site-directed mutagenesis in the catalytically relevant domains of DES, was demonstrated for the first time.

Sequence similarity networks bear out hierarchical relationships of green cytochrome P450

Land plants have diversified enzyme families. One of the most prominent is the cytochrome P450 (CYP or CYP450) family. With over 443,000 CYP proteins sequenced across the tree of life, CYPs are ubiquitous in archaea, bacteria, and eukaryotes. Here, we focused on land plants and algae to study the role of CYP diversification. CYPs, acting as monooxygenases, catalyze hydroxylation reactions crucial for specialized plant metabolic pathways, including detoxification and phytohormone production; the CYPome consists of one enormous superfamily that is divided into clans and families. Their evolutionary history speaks of high substrate promiscuity; radiation and functional diversification have yielded numerous CYP families. To understand the evolutionary relationships within the CYPs, we employed sequence similarity network analyses. We recovered distinct clusters representing different CYP families, reflecting their diversified sequences that we link to the prediction of functionalities. Hierarchical clustering and phylogenetic analysis further elucidated relationships between CYP clans, uncovering their shared deep evolutionary history. We explored the distribution and diversification of CYP subfamilies across plant and algal lineages, uncovering novel candidates and providing insights into the evolution of these enzyme families. This identified unexpected relationships between CYP families, such as the link between CYP82 and CYP74, shedding light on their roles in plant defense signaling pathways. Our approach provides a methodology that brings insights into the emergence of new functions within the CYP450 family, contributing to the evolutionary history of plants and algae. These insights can be further validated and implemented via experimental setups under various external conditions.

Epoxyalcohol Synthase Branch of Lipoxygenase Cascade

Oxylipins are one of the most important classes of bioregulators, biosynthesized through the oxidative metabolism of unsaturated fatty acids in various aerobic organisms. Oxylipins are bioregulators that maintain homeostasis at the cellular and organismal levels. The most important oxylipins are mammalian eicosanoids and plant octadecanoids. In plants, the main source of oxylipins is the lipoxygenase cascade, the key enzymes of which are nonclassical cytochromes P450 of the CYP74 family, namely allene oxide synthases (AOSs), hydroperoxide lyases (HPLs), and divinyl ether synthases (DESs). The most well-studied plant oxylipins are jasmonates (AOS products) and traumatin and green leaf volatiles (HPL products), whereas other oxylipins remain outside of the focus of researchers' attention. Among them, there is a large group of epoxy hydroxy fatty acids (epoxyalcohols), whose biosynthesis has remained unclear for a long time. In 2008, the first epoxyalcohol synthase of lancelet Branchiostoma floridae, BfEAS (CYP440A1), was discovered. The present review collects data on EASs discovered after BfEAS and enzymes exhibiting EAS activity along with other catalytic activities. This review also presents the results of a study on the evolutionary processes possibly occurring within the P450 superfamily as a whole.

Cytochrome P450 Gene Families: Role in Plant Secondary Metabolites Production and Plant Defense

Cytochrome P450s (CYPs) are the most prominent family of enzymes involved in NADPH- and O2-dependent hydroxylation processes throughout all spheres of life. CYPs are crucial for the detoxification of xenobiotics in plants, insects, and other organisms. In addition to performing this function, CYPs serve as flexible catalysts and are essential for producing secondary metabolites, antioxidants, and phytohormones in higher plants. Numerous biotic and abiotic stresses frequently affect the growth and development of plants. They cause a dramatic decrease in crop yield and a deterioration in crop quality. Plants protect themselves against these stresses through different mechanisms, which are accomplished by the active participation of CYPs in several biosynthetic and detoxifying pathways. There are immense potentialities for using CYPs as a candidate for developing agricultural crop species resistant to biotic and abiotic stressors. This review provides an overview of the plant CYP families and their functions to plant secondary metabolite production and defense against different biotic and abiotic stresses.

Ketols Emerge as Potent Oxylipin Signals Regulating Diverse Physiological Processes in Plants

Plants produce an array of oxylipins implicated in defense responses against various stresses, with about 600 oxylipins identified in plants to date. Most known oxylipins are the products of lipoxygenase (LOX)-mediated oxygenation of polyunsaturated fatty acids. One of the most well-characterized oxylipins produced by plants is the hormone jasmonic acid (JA); however, the function of the vast majority of oxylipins remains a mystery. One of the lesser-studied groups of oxylipins is comprised of ketols produced by the sequential action of LOX, allene oxide synthase (AOS), followed by non-enzymatic hydrolysis. For decades, ketols were mostly considered mere by-products of JA biosynthesis. Recent accumulating evidence suggests that ketols exhibit hormone-like signaling activities in the regulation of diverse physiological processes, including flowering, germination, plant-symbiont interactions, and defense against biotic and abiotic stresses. To complement multiple reviews on jasmonate and overall oxylipin biology, this review focuses specifically on advancing our understanding of ketol biosynthesis, occurrence, and proposed functions in diverse physiological processes.

Oxylipin biosynthesis in spikemoss Selaginella moellendorffii: Identification of allene oxide synthase (CYP74L2) and hydroperoxide lyase (CYP74L1)

Nonclassical P450s of the CYP74 family catalyse the secondary conversions of fatty acid hydroperoxides to bioactive oxylipins in plants. The model organism, spikemoss Selaginella moellendorffii Hieron, possesses at least ten CYP74 genes of novel J, K, L, and M subfamilies. The cloning of three CYP74L genes and catalytic properties of recombinant proteins are described in the present work. The CYP74L1 possessed mainly hydroperoxide lyase (HPL) activity towards the 13(S)-hydroperoxide of α-linolenic acids (13-HPOT) and nearly equal HPL and allene oxide synthase (AOS) activities towards the 13(S)-hydroperoxide of linoleic acids (13-HPOD). The 9-hydroperoxides were poor substrates for CYP74L1 and led to the production of mainly the α-ketols (AOS products) and minorities of HPL and epoxyalcohol synthase (EAS) products. The CYP74L2 possessed the AOS activity towards all tested hydroperoxides. CYP74L3 possessed low HPL/EAS activity. Besides, the aerial parts of S. moellendorffii plants possessed complex oxylipins patterns including divinyl ethers, epoxyalcohols, and 12-oxo-phytodienoic acid. Characterization of the CYP74L enzymes and oxylipin pattern updates the knowledge on the complex oxylipin biosynthetic machinery in the surviving oldest taxa of vascular plants.

Green Leaf Volatile-Burst in Selaginella moellendorffii

Green leaf volatiles (GLVs) consist of six-carbon volatile aldehydes, alcohols, and their esters. They are formed from polyunsaturated fatty acids and are involved in the defense of plants against herbivores and pathogens. GLVs generally have low concentrations in intact healthy plant tissues, but the biosynthetic pathway to form GLVs is quickly activated by mechanical damage to tissues, an event called the GLV-burst. Most seed plants have the ability to implement GLV-burst; however, this potential in non-seed plants has not been extensively researched. In this study, we examined the GLV-burst capacity of monilophytes, lycophytes, and bryophytes, and confirmed that monilophytes and lycophytes showed substantial GLV-burst ability, while bryophytes did not, with a few exceptions. When the genome sequence of a model lycophyte, Selaginella moellendorffii was reviewed, 10 genes were found that showed high similarity with the non-canonical cytochrome P450 enzymes, CYP74s, specialized in oxylipin formation. Recombinant proteins expressed with Escherichia coli showed that one of them had the ability to encode allene oxide synthase, and another encoded hydroperoxide lyase (HPL), preferring linolenic acid 13-hydroperoxide, and it was inferred that this gene was responsible for GLV-burst in S. moellendorffii. Based on the phylogenetic tree constructed with CYP74s of non-seed and seed plants, we hypothesized that HPL was acquired independently in the lycophyte and seed plants through diversification of CYP74 genes.

Plant cytochrome P450 plasticity and evolution

The superfamily of cytochrome P450 (CYP) enzymes plays key roles in plant evolution and metabolic diversification. This review provides a status on the CYP landscape within green algae and land plants. The 11 conserved CYP clans known from vascular plants are all present in green algae and several green algae-specific clans are recognized. Clan 71, 72, and 85 remain the largest CYP clans and include many taxa-specific CYP (sub)families reflecting emergence of linage-specific pathways. Molecular features and dynamics of CYP plasticity and evolution are discussed and exemplified by selected biosynthetic pathways. High substrate promiscuity is commonly observed for CYPs from large families, favoring retention of gene duplicates and neofunctionalization, thus seeding acquisition of new functions. Elucidation of biosynthetic pathways producing metabolites with sporadic distribution across plant phylogeny reveals multiple examples of convergent evolution where CYPs have been independently recruited from the same or different CYP families, to adapt to similar environmental challenges or ecological niches. Sometimes only a single or a few mutations are required for functional interconversion. A compilation of functionally characterized plant CYPs is provided online through the Plant P450 Database (erda.dk/public/vgrid/PlantP450/).

Plant cytochrome P450s: Role in stress tolerance and potential applications for human welfare

Cytochrome P450s (CYPs) are a versatile group of enzymes and one of the largest families of proteins, controlling various physiological processes via biosynthetic and detoxification pathways. CYPs perform multiple roles through a critical irreversible enzymatic reaction in which an oxygen atom is inserted within hydrophobic molecules, converting them into the reactive and hydro soluble components. During evolution, plants have acquired significantly more number of CYPs and represent about 1% of the encoded genes . CYPs are highly conserved proteins involved in growth, development and tolerance against biotic and abiotic stresses. Furthermore, CYPs reinforce plants' molecular and chemical defense mechanisms by regulating the biosynthesis of secondary metabolites, enhancing reactive oxygen species (ROS) scavenging and controlling biosynthesis and homeostasis of phytohormones, including abscisic acid (ABA) and jasmonates. Thus, they are the critical targets of metabolic engineering for enhancing plant defense against environmental stresses. Additionally, CYPs are also used as biocatalysts in the fields of pharmacology and phytoremediation. Herein, we highlight the role of CYPs in plant stress tolerance and their applications for human welfare.

Case Report: Identification of a de novo Missense Mutation in the F8 Gene, p.(Phe690Leu)/c.2070C > A, Causing Hemophilia A: A Case Report

Hemophilia A is an X-linked recessive bleeding disorder caused by various types of pathological defects in the factor VIII gene (F8/FVIII). Preimplantation genetic testing for monogenic disease (PGT-M) is a powerful tool to tackle the transmission of monogenic inherited disorders from generation to generation. In our case, a mutation in F8 had passed through female carriers in a hemophilia A family and resulted in two male patients with hemophilia A. To identify the etiological genetic variants of F8, next-generation sequencing (NGS) was used for chromosome copy number variation detection, Sanger sequencing to verify mutation sites, single nucleotide polymorphism (SNP) for site amplification, and sequencing to validate the genetic linkage. Finally, a novel missense mutation, p. (Phe690Leu)/c.2070C > A, occurring in exon 13 of F8, was screened out as a pathogenic mutation. Following this, an F8 normal euploid blastocyst was transferred. At the 18th week, the pregnant mother underwent amniocentesis, NGS, Sanger sequencing, and SNP typing that further confirmed that the fetus had a healthy genotype. After delivery, a neonatal blood sample was sent for FVIII concentration detection, and the result established that the FVIII protein was rescued to a nearly average level. We first identified a new type of pathogenic mutation in F8, which has not been previously reported, selected a genetically healthy progeny for an affected family, and provided valuable knowledge of the diagnosis and treatment of hemophilia A.