Cytochrome P450s as genes for crop improvement

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.

Unraveling the functional characterization of a jasmonate-induced flavonoid biosynthetic CYP45082G24 gene in Carthamus tinctorius

The cytochrome P450 superfamily of monooxygenases plays a major role in the evolution and diversification of plant natural products. The function of cytochrome P450s in physiological adaptability, secondary metabolism, and xenobiotic detoxification has been studied extensively in numerous plant species. However, their underlying regulatory mechanism in safflower still remained unclear. In this study, we aimed to elucidate the functional role of a putative CtCYP82G24-encoding gene in safflower, which suggests crucial insights into the regulation of methyl jasmonate-induced flavonoid accumulation in transgenic plants. The results showed that methyl jasmonate (MeJA) was associated with a progressive upregulation of CtCYP82G24 expression in safflower among other treatment conditions including light, dark, and polyethylene glycol (PEG). In addition, transgenic plants overexpressing CtCYP82G24 demonstrated increased expression level of other key flavonoid biosynthetic genes, such as AtDFR, AtANS, and AtFLS, and higher content of flavonoid and anthocyanin accumulation when compared with wild-type and mutant plants. Under exogenous MeJA treatment, the CtCYP82G24 transgenic overexpressed lines showed a significant spike in flavonoid and anthocyanin content compared with wild-type and mutant plants. Moreover, the virus-induced gene silencing (VIGS) assay of CtCYP82G24 in safflower leaves exhibited decreased flavonoid and anthocyanin accumulation and reduced expression of key flavonoid biosynthetic genes, suggesting a possible coordination between transcriptional regulation of CtCYP82G24 and flavonoid accumulation. Together, our findings confirmed the likely role of CtCYP82G24 during MeJA-induced flavonoid accumulation in safflower.

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.

Genomic and transcriptomic-based analysis of agronomic traits in sugar beet (Beta vulgaris L.) pure line IMA1

Sugar beet (Beta vulgaris L.) is an important sugar-producing and energy crop worldwide. The sugar beet pure line IMA1 independently bred by Chinese scientists is a standard diploid parent material that is widely used in hybrid-breeding programs. In this study, a high-quality, chromosome-level genome assembly for IMA1was conducted, and 99.1% of genome sequences were assigned to nine chromosomes. A total of 35,003 protein-coding genes were annotated, with 91.56% functionally annotated by public databases. Compared with previously released sugar beet assemblies, the new genome was larger with at least 1.6 times larger N50 size, thereby substantially improving the completeness and continuity of the sugar beet genome. A Genome-Wide Association Studies analysis identified 10 disease-resistance genes associated with three important beet diseases and five genes associated with sugar yield per hectare, which could be key targets to improve sugar productivity. Nine highly expressed genes associated with pollen fertility of sugar beet were also identified. The results of this study provide valuable information to identify and dissect functional genes affecting sugar beet agronomic traits, which can increase sugar beet production and help screen for excellent sugar beet breeding materials. In addition, information is provided that can precisely incorporate biotechnology tools into breeding efforts.

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.

Genome-Wide Identification of CYP72A Gene Family and Expression Patterns Related to Jasmonic Acid Treatment and Steroidal Saponin Accumulation in Dioscorea zingiberensis

Dioscorea zingiberensis is a medicinal herb containing a large amount of steroidal saponins, which are the major bioactive compounds and the primary storage form of diosgenin. The CYP72A gene family, belonging to cytochromes P450, exerts indispensable effects on the biosynthesis of numerous bioactive compounds. In this work, a total of 25 CYP72A genes were identified in D. zingiberensis and categorized into two groups according to the homology of protein sequences. The characteristics of their phylogenetic relationship, intron–exon organization, conserved motifs and cis-regulatory elements were performed by bioinformatics methods. The transcriptome data demonstrated that expression patterns of DzCYP72As varied by tissues. Moreover, qRT-PCR results displayed diverse expression profiles of DzCYP72As under different concentrations of jasmonic acid (JA). Likewise, eight metabolites in the biosynthesis pathway of steroidal saponins (four phytosterols, diosgenin, parvifloside, protodeltonin and dioscin) exhibited different contents under different concentrations of JA, and the content of total steroidal saponin was largest at the dose of 100 μmol/L of JA. The redundant analysis showed that 12 DzCYP72As had a strong correlation with specialized metabolites. Those genes were negatively correlated with stigmasterol and cholesterol but positively correlated with six other specialized metabolites. Among all DzCYP72As evaluated, DzCYP72A6, DzCYP72A16 and DzCYP72A17 contributed the most to the variation of specialized metabolites in the biosynthesis pathway of steroidal saponins. This study provides valuable information for further research on the biological functions related to steroidal saponin biosynthesis.

Role of Cytochrome P450 Enzymes in Plant Stress Response

Cytochrome P450s (CYPs) are the largest enzyme family involved in NADPH- and/or O₂-dependent hydroxylation reactions across all the domains of life. In plants and animals, CYPs play a central role in the detoxification of xenobiotics. In addition to this function, CYPs act as versatile catalysts and play a crucial role in the biosynthesis of secondary metabolites, antioxidants, and phytohormones in higher plants. The molecular and biochemical processes catalyzed by CYPs have been well characterized, however, the relationship between the biochemical process catalyzed by CYPs and its effect on several plant functions was not well established. The advent of next-generation sequencing opened new avenues to unravel the involvement of CYPs in several plant functions such as plant stress response. The expression of several CYP genes are regulated in response to environmental stresses, and they also play a prominent role in the crosstalk between abiotic and biotic stress responses. CYPs have an enormous potential to be used as a candidate for engineering crop species resilient to biotic and abiotic stresses. The objective of this review is to summarize the latest research on the role of CYPs in plant stress response.

In vitro activity and formulation of a flavonoid-containing cashew pulp extract for the topical treatment of acne and the protection of skin against premature aging

The cashew nut is an important product in Brazil, both for consumption and export, with the pulp of the cashew fruit being considered a by-product despite its high flavonoid content. In this study, the use of cashew pulp extract as a treatment for acne and in the prevention of early skin damage was investigated. Its flavonoid content was determined using spectrophotometric identification, and its effects on cell and bacterial viability, the migration of keratinocytes, and antioxidant activity in vitro were evaluated. Furthermore, it was incorporated into an emulsion for topical administration, and the physical-chemical stability parameters of the formulation were determined. The cashew pulp contained flavonoids with healing and antioxidant activity, and was not toxic to keratinocyte cells in a viability test. The flavonoid-rich formulation was stable, indicating that this is a promising formulation for use in the treatment of acne and protection of skin against premature damage.

Overexpression of the GbF3'H1 Gene Enhanced the Epigallocatechin, Gallocatechin, and Catechin Contents in Transgenic Populus

Ginkgo biloba L. leaves are a flavonoid resource for the pharmaceutical industry. The flavonoid 3'-hydroxylase (F3'H) is a key enzyme in the flavonoid biosynthesis pathway. However, the role of F3'H in flavonoid biosynthesis and metabolism is unclear. In this study, we characterized and functionally analyzed the ginkgo F3'H gene GbF3'H1 that encodes a protein of 520 amino acids. Expression profiling showed that GbF3'H1 was highly expressed in the leaves of ginkgo in September. Subcellular localization showed that GbF3'H1 occurred predominately in the cytoplasm. Transgenic poplars overexpressing GbF3'H1 had more red pigmentation in leaves than did wild-type (WT) plants. Furthermore, the concentrations of epigallocatechin, gallocatechin, and catechin in the downstream products synthesized by flavonoids were significantly higher in the transgenic plants than in the WT plants. These results indicate that the overexpression of GbF3'H1 enhances flavonoid production in transgenic plants and provides new insights into flavonoid biosynthesis and metabolism.

In vitro SPF and Photostability Assays of Emulsion Containing Nanoparticles with Vegetable Extracts Rich in Flavonoids

The aim of study was to determine the in vitro sun protection factor (SPF) and the photostability profile of a topical formulation composed of nanoparticles loaded with vegetable extracts and to assess its physicochemical properties. Chitosan/tripolyphosphate (TPP) nanoparticles loaded with flavonoids-enriched vegetable extracts (Ginkgo biloba L., Dimorphandra mollis Benth, Ruta graveolens, and Vitis vinifera L.) were produced and characterized for their morphology, mean particle size, zeta potential, and encapsulation efficiency. A final topical formulation was obtained by dispersing chitosan/TPP nanoparticles in an o/w emulsion. Results showed that nanoparticles dispersion exhibited yellowish color, spherical shape, and uniform appearance. Extract-loaded chitosan/TPP nanoparticles showed a mean particle size of 557.11 ± 3.1 nm, polydispersity index of 0.39 ± 0.27, zeta potential of + 11.54 ± 2.1 mV, and encapsulation efficiency of 75.89% of rutin. The recorded texture parameters confirm that the developed formulation is appropriate for skin application. The SPF obtained was 2.3 ± 0.4, with a critical wavelength of 387.0 nm and 0.69 UVA/UVB ratio. The developed formulation exhibited photostability, allowing the release of flavonoids from nanoparticles while retaining rutin into the skin in a higher extension.

Study of the interaction of flavonoids with 3-mercaptopropionic acid modified CdTe quantum dots mediated by cetyltrimethyl ammonium bromide in aqueous medium

Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0×10^-6molL^-1 to 6.0×10^-5molL^-1 and from 1.0×10^-5molL^-1 to 6.0×10^-4molL^-1 for kaempferol. The sensibility of the Stern-Volmer curves (K_s) indicated that quercetin interacts more strongly with the probe: K_{s quercetin}>K_{s kaempferol}>K_{s rutin}>K_{s morin}. The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3'and 4') in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10^-5molL^-1 level. In CTAB organized dispersions, K_{s 3-hydroxyflavone}>K_{s 7-hydroxyflavone}>K_{s flavona}>K_{s rutin} in the range from 1.0×10^-6molL^-1 to 1.2×10^-5molL^-1 for flavones and of 1.0×10^-6molL^-1 to 1.0×10^-5molL^-1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs.

Differential expression of genes in purple-shoot tea tender leaves and mature leaves during leaf growth

BACKGROUND

Tea (Camellia sinensis L.), contains high levels of secondary metabolic products with both commercial and medicinal value. At present, most cultivated tea plant have green leaves; although tea plants with purple leaves exist, their supply is inadequate. During leaf growth and maturation, the content of secondary metabolic compounds decreases, resulting in higher content in tender purple leaves (TPL), and lower content in mature green leaves (MGL). The aim of this study was to analyze the differential expression of genes in these two tissues, with a cDNA-AFLP (amplified fragment length polymorphism) approach and biochemical analysis.

RESULTS

Compared to MGL samples, TPL samples had higher content of anthocyanin, total polyphenols and total catechins, a higher carotenoid-to-chlorophyll ratio and lower content of soluble sugars (glucose, fructose and sucrose). TPL samples showed a lower photosynthetic ability, demonstrated by a lower CO2 assimilation and carbohydrate accumulation rate. Using cDNA-AFLP with 256 primer combinations, differential transcript profiling generated 148 matched transcript-derived fragments (TDFs). Among these TDFs, 77 genes were upregulated and 71 were downregulated. These were grouped into 11 functional categories which are important for final tea quality parameters.

CONCLUSIONS

Our data presented the first effort to elucidate the molecular basis of differential accumulation of key metabolites during tea leaf maturation. Our findings also provided a theoretical molecular explanation for the color change during leaf growth.

A Decade of Molecular Understanding of Withanolide Biosynthesis and In vitro Studies in Withania somnifera (L.) Dunal: Prospects and Perspectives for Pathway Engineering

Withania somnifera, a multipurpose medicinal plant is a rich reservoir of pharmaceutically active triterpenoids that are steroidal lactones known as withanolides. Though the plant has been well-characterized in terms of phytochemical profiles as well as pharmaceutical activities, limited attempts have been made to decipher the biosynthetic route and identification of key regulatory genes involved in withanolide biosynthesis. This scenario limits biotechnological interventions for enhanced production of bioactive compounds. Nevertheless, recent emergent trends vis-à-vis, the exploration of genomic, transcriptomic, proteomic, metabolomics, and in vitro studies have opened new vistas regarding pathway engineering of withanolide production. During recent years, various strategic pathway genes have been characterized with significant amount of regulatory studies which allude toward development of molecular circuitries for production of key intermediates or end products in heterologous hosts. Another pivotal aspect covering redirection of metabolic flux for channelizing the precursor pool toward enhanced withanolide production has also been attained by deciphering decisive branch point(s) as robust targets for pathway modulation. With these perspectives, the current review provides a detailed overview of various studies undertaken by the authors and collated literature related to molecular and in vitro approaches employed in W. somnifera for understanding various molecular network interactions in entirety.

Expression of TaCYP78A3, a gene encoding cytochrome P450 CYP78A3 protein in wheat (Triticum aestivum L.), affects seed size

Several studies have described quantitative trait loci (QTL) for seed size in wheat, but the relevant genes and molecular mechanisms remain largely unknown. Here we report the functional characterization of the wheat TaCYP78A3 gene and its effect on seed size. TaCYP78A3 encoded wheat cytochrome P450 CYP78A3, and was specifically expressed in wheat reproductive organs. TaCYP78A3 activity was positively correlated with the final seed size. Its silencing caused a reduction of cell number in the seed coat, resulting in an 11% decrease in wheat seed size, whereas TaCYP78A3 over-expression induced production of more cells in the seed coat, leading to an 11-48% increase in Arabidopsis seed size. In addition, the cell number in the final seed coat was determined by the TaCYP78A3 expression level, which affected the extent of integument cell proliferation in the developing ovule and seed. Unfortunately, TaCYP78A3 over-expression in Arabidopsis caused a reduced seed set due to an ovule developmental defect. Moreover, TaCYP78A3 over-expression affected embryo development by promoting embryo integument cell proliferation during seed development, which also ultimately affected the final seed size in Arabidopsis. In summary, our results indicated that TaCYP78A3 plays critical roles in influencing seed size by affecting the extent of integument cell proliferation. The present study provides direct evidence that TaCYP78A3 affects seed size in wheat, and contributes to an understanding of the cellular basis of the gene influencing seed development.

Evolution and association analysis of GmCYP78A10 gene with seed size/weight and pod number in soybean

Seed-size/weight traits, controlled by multiple genes in soybean, play an important role in determining seed yield. However, the molecular mechanisms controlling the seed size and weight in soybean remain unclear. In Arabidopsis, P450/CYP78A gene family has been proved extremely relevant to seed size (such as AtCYP78A5, AtCYP78A6 and AtCYP78A9). We found that a soybean GmCYP78A10 gene underwent artificial selection during soybean breeding. The GmCYP78A10a allele mainly distributed in wild soybean (Glycine soja), but has been eliminated in the cultivars during early stage of soybean breeding, while the GmCYP78A10b allele has been accumulated and become the predominant allele in cultivated soybean (G. max). ANOVA analysis showed that the mean seed weight, seed width and seed thickness of soybean varieties with GmCYP78A10b allele was significantly heavier/bigger than those with GmCYP78A10a allele (P < 0.01). The allele could explain 7.2 % variation in seed weight. The pod number of the soybeans with GmCYP78A10b allele significantly decreased compared to those with GmCYP78A10a allele (P < 0.01, R(2) = 5.8 %), while other agronomic traits including seed weight/plant were not significantly affected by these two alleles. We speculated that during the early stage of soybean breeding, breeders selected big seed carrying GmCYP78A10b allele, but lowered pod number simultaneously. Overall, the selection did not cause the significantly change in soybean seed yield. Our results suggests that the soybean GmCYP78A10 gene may have a similar function to those genes belonging to P450/CYP78A subfamily in Arabidopsis and provides new information for the genetic control of seed size in soybean.

Molecular cloning, bacterial expression and functional characterisation of cytochrome P450 monooxygenase, CYP97C27, and NADPH-cytochrome P450 reductase, CPR I, from Croton stellatopilosus Ohba

The cDNAs for cytochrome P450 monooxygenase (designated as CYP97C27 by D. Nelson's group) and NADPH-cytochrome P450 reductase (designated as CPR I based on its classification) were isolated from Croton stellatopilosus leaves, which actively biosynthesise plaunotol (18-OH geranylgeraniol). CYP97C27 and CPR I contain open reading frames encoding proteins of 471 and 711 amino acids with predicted molecular masses of 53 and 79kDa, respectively. By aligning the deduced sequences of CYP97C27 and CPR I with other plant species, all functional domains of CYP97C27 (heme and oxygen binding) and CPR I (CYP- and FMN, FAD, and NADPH cofactor binding) were identified. Amino acid sequence comparison indicated that both CYP97C27 (85-93%) and CPR I (79-83%) share high sequence identities with homologous proteins in other plant species, suggesting that CYP97C27 belongs to the CYP97C subfamily and that CPR I belongs to class I of the dicotyledonous CPR. Functional characterisation of both enzymes, produced in Escherichia coli (pET32a/BL21(DE3)) as recombinant proteins, showed that simultaneous incubation of CYP97C27 and CPR I with the substrate geranylgeraniol (GGOH) and coenzyme NADPH led to formation of the product plaunotol. In C. stellatopilosus, the levels of the CYP97C27 and CPR I transcripts were highly correlated with those of several mRNAs involved in the plaunotol biosynthetic pathway, suggesting that CYP97C27 and CPR I are the enzymes that catalyse the last hydroxylation step of the pathway.

Cloning and expression of a CYP720B orthologue involved in the biosynthesis of diterpene resin acids in Pinus brutia

Cytochrome P450 monooxygenases mediate a broad range of oxidative reactions involved in the biosynthesis of both primary and secondary metabolites in plants. Until now, only two P450 genes, CYP720B1 from Pinus taeda and CYP720B4 from Picea sitchensis, have been functionally characterised and described in the literature. The purpose of this study was to describe the cloning and expression of CYP720B from Pinus brutia due to its suggested role in the synthesis of bioactive compounds used for chemical defence against insects. A PCR product of the P. brutia CYP720B gene was cloned into the pCR8/GW/TOPO cloning vector. After optimising the sequence for codon usage in yeast, it was transferred into the inducible expression vector pYES-DEST52 and transfected into the S. cerevisiae INVSc1 strain. Sequence analysis showed that the P. brutia CYP720B gene contains an open reading frame of 1,464 nucleotides, which encodes a 53,570 Da putative protein of 487 amino acid residues. The putative protein contains the classic heme-binding sequence motif that is conserved in all P450 enzymes. It shares 99 and 61% identity with the deduced amino acid sequences of CYP720B1 from Pinus taeda and CYP720B4 from Picea sitchensis, respectively. Recombinant CYP720B protein expression was confirmed using western blot analysis. Furthermore, recombinant CYP720B was functionally active, showing a Soret peak at approximately 448 nm in the reduced CO difference spectra. These data suggest that the cloned gene is an orthologue of CYP720B in P. brutia and might be involved in DRA biosynthesis.

Drought stress-induced compositional changes in tolerant transgenic rice and its wild type

Comparing well-watered versus deficit conditions, we evaluated the chemical composition of grains harvested from wild-type (WT) and drought-tolerant, transgenic rice (Oryza sativa L.). The latter had been developed by inserting AtCYP78A7, which encodes a cytochrome P450 protein. Two transgenic Lines, '10B-5' and '18A-4', and the 'Hwayoung' WT were grown under a rainout shelter. After the harvested grains were polished, their levels of key components, including proximates, amino acids, fatty acids, minerals and vitamins were analysed to determine the effect of watering system and genotype. Drought treatment significantly influenced the levels of some nutritional components in both transgenic and WT grains. In particular, the amounts of lignoceric acid and copper in the WT decreased by 12.6% and 39.5%, respectively, by drought stress, whereas those of copper and potassium in the transgenics rose by 88.1-113.3% and 10.4-11.9%, respectively, under water-deficit conditions.

NADPH-cytochrome P450 reductase: molecular cloning and functional characterization of two paralogs from Withania somnifera (L.) dunal

Withania somnifera (L.) Dunal, a highly reputed medicinal plant, synthesizes a large array of steroidal lactone triterpenoids called withanolides. Although its chemical profile and pharmacological activities have been studied extensively during the last two decades, limited attempts have been made to decipher the biosynthetic route and identification of key regulatory genes involved in withanolide biosynthesis. Cytochrome P450 reductase is the most imperative redox partner of multiple P450s involved in primary and secondary metabolite biosynthesis. We describe here the cloning and characterization of two paralogs of cytochrome P450 reductase from W. somnifera. The full length paralogs of WsCPR1 and WsCPR2 have open reading frames of 2058 and 2142 bp encoding 685 and 713 amino acid residues, respectively. Phylogenetic analysis demonstrated that grouping of dual CPRs was in accordance with class I and class II of eudicotyledon CPRs. The corresponding coding sequences were expressed in Escherichia coli as glutathione-S-transferase fusion proteins, purified and characterized. Recombinant proteins of both the paralogs were purified with their intact membrane anchor regions and it is hitherto unreported for other CPRs which have been purified from microsomal fraction. Southern blot analysis suggested that two divergent isoforms of CPR exist independently in Withania genome. Quantitative real-time PCR analysis indicated that both genes were widely expressed in leaves, stalks, roots, flowers and berries with higher expression level of WsCPR2 in comparison to WsCPR1. Similar to CPRs of other plant species, WsCPR1 was un-inducible while WsCPR2 transcript level increased in a time-dependent manner after elicitor treatments. High performance liquid chromatography of withanolides extracted from elicitor-treated samples showed a significant increase in two of the key withanolides, withanolide A and withaferin A, possibly indicating the role of WsCPR2 in withanolide biosynthesis. Present investigation so far is the only report of characterization of CPR paralogs from W. somnifera.

Characterization of two NADPH: cytochrome P450 reductases from cotton (Gossypium hirsutum)

Cytochrome P450 monooxygenases (P450s) are commonly involved in biosynthesis of endogenous compounds and catabolism of xenobiotics, and their activities rely on a partner enzyme, cytochrome P450 reductase (CPR, E.C.1.6.2.4). Two CPR cDNAs, GhCPR1 and GhCPR2, were isolated from cotton (Gossypium hirsutum). They are 71% identical to each other at the amino acid sequence level and belong to the Class I and II of dicotyledonous CPRs, respectively. The recombinant enzymes reduced cytochrome c, ferricyanide and dichlorophenolindophenol (DCPIP) in an NADPH-dependent manner, and supported the activity of CYP73A25, a cinnamate 4-hydroxylase of cotton. Both GhCPR genes were widely expressed in cotton tissues, with a reduced expression level of GhCPR2 in the glandless cotton cultivar. Expression of GhCPR2, but not GhCPR1, was inducible by mechanical wounding and elicitation, indicating that the GhCPR2 is more related to defense reactions, including biosynthesis of secondary metabolites.

Differential expression of candidate genes for lignin biosynthesis under drought stress in maize leaves

In order to provide information for the development of molecular selection markers for drought tolerance improvement, the methods of prometric analysis, quantitative real-time PCR and field evaluation were employed for the identification of the differential expression of candidate genes under drought stress in maize. At seventeen, twenty-four and forty-eight hours of polyethylene glycol-simulated drought stress at the seventh leaf stage, leaf samples were collected from two drought-tolerant inbred lines for prometric analysis by two-dimensional electrophoresis and peptide mass fingerprinting. Fifty-eight proteins out of more than 500 were found in response to drought stress. Three drought-induced spots 2506, 3507 and 4506 showed sequence similarity with cinnamyl alcohol dehydrogenase, cytochrome protein 96A8 and S-adenosyl-L-methionine synthase, respectively. The expression of two key enzymes to lignin biosynthesis was quantified by quantitative real-time PCR among three drought-tolerant and one drought-sensitive inbred lines under drought stress and well-watered control conditions. After a decrease at the beginning of drought stress, the expression of cinnamyl alcohol dehydrogenase and caffeate O-methyltransferase recovered at twenty-four hours of the drought stress in the three drought-tolerant lines, but not in the drought-sensitive lines. Leaf lignin content, anthesis-silking interval and grain weight per plant were investigated with six inbred lines of varying drought tolerance under drought stress and well-watered control. Drought tolerance coefficients of these three characters were calculated and the correlation coefficients among these drought tolerance coefficients were estimated. Significant difference in leaf lignin content was found among the inbred lines and in response to drought stress. Close correlations were observed between the drought tolerant coefficients for leaf lignin content and grain weight per plant, and between the drought tolerant coefficients for leaf lignin content and anthesis-silking interval. These results indicate that leaf lignin content is a useful index for evaluation of drought tolerance in maize. Molecular selection markers can be developed on the basis of differential expression of the candidate genes and applied to maize improvement for drought tolerance.

Expression analysis of defense-related genes in wheat in response to infection by Fusarium graminearum

Fusarium head blight (FHB), caused by the fungi Fusarium graminearum and Fusarium culmorum, is a worldwide disease of wheat (Triticum aestivum L.). The Chinese cultivar Ning 7840 is one of a few wheat cultivars with resistance to FHB. GeneCalling, an open-architecture mRNA-profiling technology, was used to identify differentially expressed genes induced or suppressed in spikes of Ning 7840 after infection by F. graminearum. One hundred and twenty-five cDNA fragments representing transcripts differentially expressed in wheat spikes were identified. Based on BLASTN and BLASTX analyses, putative functions were assigned to some of the genes: 28 were assigned functions in primary metabolism and photosynthesis, 7 were involved in defense response, 14 were involved in gene expression and regulation, 24 encoded proteins associated with structure and protein synthesis, 42 lacked homology to sequences in the database, and 3 were similar to cloned multidrug resistance or disease resistance proteins. Of particular interest in this study were genes associated with resistance and defense against pathogen infection. Real-time quantitative reverse-transcription PCR indicated that of 51 genes tested, 19 showed 2-fold or greater induction or suppression in infected Ning 7840 in comparison with the water-treated control. The remaining 32 genes were not significantly induced or suppressed in infected Ning 7840 compared with the control. Subsequently, these 19 induced or suppressed genes were examined in the wheat line KS24-1, containing FHB resistance derived from Lophopyrum elongatum, and Len, an FHB-susceptible wheat cultivar. The temporal expression of some of these sequences encoding resistance proteins or defense-related proteins showed FHB (resistance specific) induction, suggesting that these genes play a role in protection against toxic compounds in plant-fungus interactions. On the basis of comprehensive expression profiling of various biotic or abiotic stress response genes revealed by quantitative PCR in this study and other supporting data, we hypothesized that the plant-pathogen interactions may be highly integrated into a network of diverse biosynthetic pathways.

Identification of a cytochrome P450 cDNA (CYP98A5) from Phaseolus vulgaris, inducible by 3,5-dichlorosalicylic acid and 2,6-dichloro isonicotinic acid

To investigate the involvement of cytochrome P450s in the metabolism of plants treated with xenobiotic agrochemicals, bean leaves were treated with 3,5-dichlorosalicylic acid (DC-SA), a priming agent of plant defense and 2,6-dichloroisonicotinic acid (DC-INA), a chemical inducer of systemic acquired resistance. Through the use of directed differential display reverse transcription polymerase chain reactions, a differentially expressed cDNA amplicon, found to be up-regulated by both DC-SA and DC-INA treatment, was identified as a cytochrome P450 cDNA, CYP98A5. The nucleotide sequence indicates extensive homology to 3'-hydroxylases of p-coumaroyl esters. Dot blot analysis of leaves treated with various SA and isonicotinic acid derivatives showed enhanced expression of CYP98A5 due to DC-SA and DC-INA. Northern blot analysis of a time-dependent induction study of CYP98A5 in treated bean leaves indicated that DC-SA induces CYP98A5 mRNA transcripts earlier than DC-INA. Both inducers resulted in high transcript levels 24-48 h after treatment. The up-regulation of CYP98A5 is supportive of the conditioning and sensitizing effects of DC-SA and DC-INA to elicit a more rapid and effective defense response.

Functional analysis of a novel male fertility CYP86MF gene in Chinese cabbage (Brassica campestris L. ssp. chinensis makino)

In our earlier work, a cytochrome P450 CYP86MF gene was isolated from floral bud of Chinese cabbage (Brassica campestris L. ssp. chinensis Makino, syn. B. rapa L.) by mRNA differential display PCR (DD-PCR) and rapid amplification of cDNA ends (RACE). To unravel the biological function of CYP86MF gene, the antisense fragment from the CYP86MF gene was transferred into Chinese cabbage pak-choi (B. campestris ssp. chinensis var. communis Tsen et Lee). Out of 22 plants transformed with the antisense gene constructed from the CYP86MF, 20 reached to flowering stage. Morphological investigations showed that the transgenic plants developed the normal floral organ. However, they remained self-infertile, even when artificial self-pollination was performed in the bud stage. Pollen germination test indicated that the pollen from the transgenic line TB-2 could not germinate normally. Further physiological, biochemical and cytological analyses showed that only significant difference was detectable in contents of the endogenous hormones, and a layer of unknown material adhered to the surface of microspore. The present studies thus provided valuable clues for understanding the biological function of the CYP86C subfamily genes. Furthermore, our studies also demonstrate a novel method for obtaining artificial male sterility line of Chinese cabbage.

Modified nicotine metabolism in transgenic tobacco plants expressing the human cytochrome P450 2A6 cDNA

In this study, the human cytochrome P450 (CYP) 2A6 was used in order to modify the alkaloid production of tobacco plants. The cDNA for human CYP2A6 was placed under the control of the constitutive 35S promoter and transferred into Nicotiana tabacum via Agrobacterium-mediated transformation. Transgenic plants showed formation of the recombinant CYP2A6 enzyme but no obvious phenotypic changes. Unlike wild-type tobacco, the transgenic plants accumulated cotinine, a metabolite which is usually formed from nicotine in humans. This result substantiates that metabolic engineering of the plant secondary metabolism via mammalian P450 enzymes is possible in vivo.

cDNA-AFLP reveals genes differentially expressed during the hypersensitive response of cassava

SUMMARY The tropical staple cassava is subject to several major diseases, such as cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis. Disease-resistant genotypes afford the only practical solution, yet despite the global importance of this crop, little is known about its defence mechanisms. cDNA-AFLP was used to isolate cassava genes differentially expressed during the hypersensitive reaction (HR) of leaves in response to an incompatible Pseudomonas syringae pathovar. Seventy-eight transcript-derived fragments (TDFs) showing differential expression (c. 75% up-regulated, 25% down-regulated) were identified. Many encoded putative homologues of known defence-related genes involved in signalling (e.g. calcium transport and binding, ACC oxidases and a WRKY transcription factor), cell wall strengthening (e.g. cinnamoyl coenzyme A reductase and peroxidase), programmed cell death (e.g. proteases, 26S proteosome), antimicrobial activity (e.g. proteases and beta-1,3-glucanases) and the production of antimicrobial compounds (e.g. DAHP synthase and cytochrome P450s). Full-length cDNAs including a probable matrix metalloprotease and a WRKY transcription factor were isolated from six TDFs. RT-PCR or Northern blot analysis showed HR-induced TDFs were maximally expressed at 24 h, although some were produced by 6 h; some were induced, albeit more slowly, in response to wounding. This work begins to reveal potential defence-related genes of this understudied, major crop.

CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana

Brassinosteroids (BRs) are plant hormones that are essential for a wide range of developmental processes in plants. Many of the genes responsible for the early reactions in the biosynthesis of BRs have recently been identified. However, several genes for enzymes that catalyze late steps in the biosynthesis pathways of BRs remain to be identified, and only a few genes responsible for the reactions that produce bioactive BRs have been identified. We found that the ROTUNDIFOLIA3 (ROT3) gene, encoding the enzyme CYP90C1, which was specifically involved in the regulation of leaf length in Arabidopsis thaliana, was required for the late steps in the BR biosynthesis pathway. ROT3 appears to be required for the conversion of typhasterol to castasterone, an activation step in the BR pathway. We also analyzed the gene most closely related to ROT3, CYP90D1, and found that double mutants for ROT3 and CYP90D1 had a severe dwarf phenotype, whereas cyp90d1 single knockout mutants did not. BR profiling in these mutants revealed that CYP90D1 was also involved in BR biosynthesis pathways. ROT3 and CYP90D1 were expressed differentially in leaves of A. thaliana, and the mutants for these two genes differed in their defects in elongation of hypocotyls under light conditions. The expression of CYP90D1 was strongly induced in leaf petioles in the dark. The results of the present study provide evidence that the two cytochrome P450s, CYP90C1 and CYP90D1, play distinct roles in organ-specific environmental regulation of the biosynthesis of BRs.

Pest and disease resistance enhanced by heterologous suppression of a Nicotiana plumbaginifolia cytochrome P450 gene CYP72A2

The functional role of the Nicotiana plumbaginifolia cytochrome P450 gene CYP72A2 was investigated in transgenic plants. N. tabacum plants transformed with a sense or antisense CYP72A2 construct exhibited diminished heights, branched stems, smaller leaves and deformed flowers. Western blot analysis revealed reduced levels of a 58 kDa protein corresponding to CYP72A2, suggesting that the CYP72A2 homolog was suppressed in the sense and antisense plants. Transgenic plants had increased resistance to Manduca sexta larvae that consumed about 35 to 90 less of transgenic versus control leaves. A virulent strain of Pseudomonas syringae pv. tabaci induced a disease-limiting response followed by a delayed and decreased development of disease symptoms in the transgenics. CYP72A2 gene mediated resistance suggests that the plant-pest or -pathogen interactions may have been modified by changes in bioactive metabolite pools.

Gene expression profiling of systemically wound-induced defenses in hybrid poplar

As part of an ongoing effort to identify genes involved in poplar defense responses, and to provide a resource for comparative analysis of woody and non-woody plant defense, we generated expressed sequence tags (ESTs) from a library constructed from systemically wounded leaves of hybrid poplar (Populus trichocarpa x P. deltoides). Partial sequences were obtained from the 5' ends of 928 individual cDNAs, which could be grouped into 565 non-overlapping sequences. Of these, 447 sequences were singletons, while the remainder fell into 118 clusters containing up to 17 partially overlapping ESTs. Approximately 81% of the EST sequences showed similarity to previously described sequences in public databases. Of these, the distribution of gene functions within the EST set indicated that approximately 11% of the ESTs encode proteins potentially involved in defense or secondary metabolism, while photosynthesis and primary metabolism accounted for 45% of the expressed genes. Two types of defense proteins, Kunitz trypsin inhibitors and chitinases, were found among the ten most abundant ESTs, indicating the significant impact of wounding on the leaf transcriptome and suggesting that these functions are important for hybrid poplar defense. In the course of this work, three new wound-inducible Kunitz trypsin inhibitor-like genes and two new chitinase-like genes were characterized. A suite of other systemically wound-induced genes were identified using northern and macroarray analysis, indicating diversity and multiplicity in the induced defense response. Overall, we demonstrate that defense-related genes of hybrid poplar have a variety of functions, and show remarkably diverse expression patterns upon wounding.

Cloning, functional expression, and subcellular localization of multiple NADPH-cytochrome P450 reductases from hybrid poplar

NADPH:cytochrome P450 reductase (CPR) provides reducing equivalents to diverse cytochrome P450 monooxygenases. We isolated cDNAs for three CPR genes (CPR1, CPR2, and CPR3) from hybrid poplar (Populus trichocarpa x Populus deltoides). Deduced CPR2 and CPR3 amino acid sequences were 91% identical, but encoded isoforms divergent from CPR1 (72% identity). CPR1 and CPR2 were co-expressed together with the P450 enzyme cinnamate-4-hydroxylase (C4H) in yeast (Saccharomyces cerevisiae). Microsomes isolated from strains expressing CPR1/C4H or CPR2/C4H enhanced C4H activities approximately 10-fold relative to the C4H-only control strain, and catalyzed NADPH-dependent cytochrome c reduction. The divergent CPR isoforms (CPR1 and CPR2/3) contained entirely different N-terminal sequences, which are conserved in other plant CPRs and are diagnostic for two distinct classes of CPRs within the angiosperms. C-terminal green fluorescent protein fusions to CPR1 and CPR2 were constructed and expressed in both yeast and Arabidopsis. The fusion proteins expressed in yeast retained the ability to support C4H activity and, thus, were catalytically active. Both CPR::green fluorescent protein fusion proteins were strictly localized to the endoplasmic reticulum in transgenic Arabidopsis. The lack of localization of either isoform to chloroplasts, where P450s are known to be present, suggests that an alternative P450 reduction system may be operative in this organelle. Transcripts for the three poplar CPR genes were present ubiquitously in all tissues examined, but CPR2 showed highest expression in young leaf tissue.

Flavonoids-potent and versatile biologically active compounds interacting with cytochromes P450

Flavonoids represent a group of phytochemicals exhibiting a wide range of biological activities arising mainly from their antioxidant properties and ability to modulate several enzymes or cell receptors. Flavonoids have been recognized to exert anti-bacterial and anti-viral activity, anti-inflammatory, anti-angionic, analgesic, anti-allergic effects, hepatoprotective, cytostatic, apoptotic, estrogenic and anti-estrogenic properties. However, not all flavonoids and their actions are necessarily beneficial. Some flavonoids have mutagenic and/or prooxidant effects and can also interfere with essential biochemical pathways. Among the proteins that interact with flavonoids, cytochromes P450 (CYPs), monooxygenases metabolizing xenobiotics (e.g. drugs, carcinogens) and endogenous substrates (e.g. steroids), play a prominent role. Flavonoid compounds influence these enzymes in several ways: flavonoids induce the expression of several CYPs and modulate (inhibit or stimulate) their metabolic activity. In addition, some CYPs participate in metabolism of flavonoids. Flavonoids enhance activation of carcinogens and/or influence the metabolism of drugs via induction of specific CYPs. On the other hand, inhibition of CYPs involved in carcinogen activation and scavenging reactive species formed from carcinogens by CYP-mediated reactions can be beneficial properties of various flavonoids. Flavonoids show an estrogenic or anti-estrogenic activity owing to the structural similarity with the estrogen skeleton. Mimicking natural estrogens, they bind to estrogen receptor and modulate its activity. They also block CYP19, a crucial enzyme involved in estrogen biosynthesis. Flavonoids in human diet may reduce the risk of various cancers, especially hormone-dependent breast and prostate cancers, as well preventing menopausal symptoms. For these reasons the structure-function relationship of flavonoids is extensively studied to provide an inspiration for a rational drug and/or chemopreventive agent design of future pharmaceuticals.