Natural pyrethrin insecticides produced by Dalmatian pyrethrum (Tanacetum cinerariifolium) have low mammalian toxicity and short environmental persistence, providing an alternative to widely used ...synthetic agricultural insecticides that pose a threat to human health and the environment. A recent surge of interest in the use of pyrethrins as agricultural insecticides coincides with the discovery of several new genes in the pyrethrin biosynthetic pathway. Elucidation of this pathway facilitates efforts to breed improved pyrethrum varieties and to engineer plants with improved endogenous defenses or hosts for heterologous pyrethrin production. We describe the current state of knowledge related to global pyrethrum production, the pyrethrin biosynthetic pathway and its regulation, and recent efforts to engineer the pyrethrin pathway in diverse plant hosts.
Pyrethrin insecticides produced by Tanacetum cinerariifolium provide a human-safe and ecologically sound alternative to widely used synthetic insecticides.The development of transcriptomic and genomic resources for T. cinerariifolium facilitated the elucidation of numerous steps in the pyrethrin biosynthetic pathway.Pyrethrin biosynthetic genes have been engineered into diverse plant hosts; these efforts demonstrate the promise of engineering plants with improved endogenous defenses or of the development of an alternative source to pyrethrins for use as insecticides.
Sekundarni metaboliti biljaka imaju važnu ulogu u reakciji biljaka na abiotički i biotički stres. Neke od bioaktivnih komponenti imaju izražena insekticidna svojstva, pa onda govorimo o insekticidnim ...biljkama poput dalmatinskog (Tanacetum cinerariifolium /Trevir./ Sch. Bip.) i kavkaškog buhača (Tanacetum coccineum (Willd.) Grierson) (aktivne komponente - piretrini), duhana (nikotin), neema (azadirahtin) i dr. Botanički insekticidi su uglavnom kraće perzistentnosti, pa su na osnovi njihove kemijske strukture razvijeni stabilniji sintetski insekticidi – piretroidi i neonikotinoidi, S ograničavanjem primjene kemijskih insekticida, botanički insekticidi dobivaju sve značajniju ulogu i u konvencionalnoj zaštiti bilja, ne samo ekološkoj. Posebno su značajni prirodni piretrini. Zbog brze razgradnje imaju kratku karencu što je često nedostatak, ali je i prikladno za zaštitu bilja prije same berbe, što je posebno prikladno kod suzbijanja octene mušice ploda.
► Pyrethrum seed germination was best under dark conditions. ► Increasing salt and drought stress inhibited seed germination and seedling growth. ► Pyrethrum seedlings grew well at osmotic potential ...≥−0.6
MPa in NaCl. ► The inhibition of salts on germination resulted from drought stress rather than salt toxicity. ► Hydropriming is effective to improve germination under salt and drought stress.
Poor germination and seedling establishment are major problems in arid and semi-arid environments, and these characteristics are considered to be important factors in later plant growth and yield. Laboratory experiments were conducted on freshly harvested pyrethrum (
Tanacetum cinerariifolium) seeds to investigate the effects of light (influenced by the seeding method) and seed hydropriming on germination, and shoot and root growth at 25
°C. Exposure to light could reduce germination from 52% to 22% and increase the mean germination time (MGT) from 7 to 12 days. The responses of hydroprimed and unprimed seeds to salt and drought stress were determined at osmotic potentials of 0 (distilled water), −0.3, −0.6, −0.9, −1.2
MPa in NaCl and PEG6000. Seed germination and seedling growth were inhibited by increasing salt and drought stress. The germination percentage of unprimed seeds was reduced from 52% to 16% in −1.2
MPa NaCl, and no seeds germinated at osmotic potentials ≤−0.9
MPa PEG. Both shoot and root growth were inhibited at osmotic potentials ≤−0.9
MPa NaCl and ≤−0.6
MPa PEG. Hydropriming shortened the delay of MGT at all osmotic potentials, and improved the germination percentage in distilled water (from 52% to 59%) and resistance to salt stress with nearly double germination (from 16% to 29%) at the highest salt concentration. When non-germinated seeds were transferred to distilled water after 20 days of incubation in total up to 12–15% of NaCl and 25–27% of PEG stressed seeds did not recover. These results show that the inhibition of the germination and seedling growth at the same osmotic potential of NaCl and PEG resulted from drought stress rather than salt toxicity, and that hydropriming is an effective tool to improve the quality of pyrethrum seeds.
Plant defensive mimicry based on the aphid alarm pheromone (E)-β-farnesene (EβF) was previously shown to operate in Tanacetum cinerariifolium (Asteraceae) flowers. Germacrene D (GD), is another ...dominant volatile of T. cinerariifolium flowers and may modulate both defense and pollination. Here, we find that the increase in GD/EβF ratio at later developmental stages is correlated with the tissue distribution in the flower head: the total content of EβF and GD is similar, but GD accumulates comparatively more in the upper disk florets. Naphthol and N, N-dimethyl-p-phenylenediamine dihydrochloride (NADI)-stained purple ducts containing EβF and GD, were observed in the five petal lips of the corolla and two-lobed stigma of disk florets. By contrast in the peduncle, EβF accounts for nearly 80% of total terpenes, compared to 5% for GD. EβF is accumulated inside inner cortex cells and parenchyma cells of the pith in young peduncle. This is followed by the formation of terpene-filled axial secretory cavities parallel to the vascular bundles. In conclusion, the observed developmental and diurnal emissions of different EβF/GD ratios appear to be regulated by their tissue distribution.
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•EβF and GD are the dominant volatiles with similar contents in pyrethrum flowers.•GD accumulates comparatively more in the upper disk florets.•EβF and GD were observed in the five petal lips of the corolla and two-lobed stigma of disk florets.•In peduncle, EβF was accumulated in the cortex cells and further stored in the secretory ducts.
Pyrethrins, synthesized in the perennial plant
, are a class of terpene mixtures with high insecticidal activity and low human toxicity, which are widely used in plant-derived pesticides. Numerous ...studies have identified multiple pyrethrins biosynthesis enzymes, which can be enhanced by exogenous hormones such as methyl jasmonate (MeJA). However, the mechanism by which hormone signaling regulates pyrethrins biosynthesis and the potential involvement of certain transcription factors (TFs) remain unclear. In this study, we found that the expression level of a TF in
was significantly increased after treatment with plant hormones (MeJA, abscisic acid). Subsequent analysis identified this TF as a member of the basic region/leucine zipper (bZIP) family and was thus named
. TcbZIP60 was localized in the nucleus, suggesting that it is involved in the transcription process. The expression profiles of
were similar to those of pyrethrins synthesis genes in different flower organs and at different flowering stages. Furthermore, TcbZIP60 could directly bind to the E-box/G-box motifs in the promoters of the pyrethrins synthesis genes
and
to activate their expression. Transient overexpression of
increased the expression levels of pyrethrins biosynthesis genes, leading to the significant accumulation of pyrethrins. Silencing of
significantly downregulated pyrethrins accumulation and the expression of related genes. Overall, our results reveal a novel TF, TcbZIP60, that regulates both the terpenoid and jasmonic acid pathways of pyrethrins biosynthesis in
.
Seeds collected from 10 Dalmatian pyrethrum (Tanacetum cinerariifolium /Trevir./ Sch. Bip. Asteraceae) populations naturally occurring along the Adriatic coast and islands, were used to establish a ...common garden with the aim of estimating the variation of pyrethrin compounds between and within populations. A recently optimized matrix solid phase dispersion (MSPD) method was used for the extraction of six pyrethrin compounds from dry flower heads of 200 Dalmatian pyrethrum individuals. Separation and quantification of pyrethrin compounds were performed by high performance liquid chromatography with diode array detector (HPLC-DAD). High variability in pyrethrin content and composition was observed within and between populations. Total pyrethrin content in individual samples varied from 0.10% to 1.35% of flower dry weight. On average, the lowest total pyrethrin content was observed in the population of Pelješac (0.22%) and the highest in the island populations of Mali Lošinj and Zlarin (0.87%). The population of Mali Lošinj had the most favourable pyrethrin profile, including the lowest variability in total pyrethrin content, the highest pyrethrin I (PI) content (up to 60.47%) and PI/PII ratio (up to 5.88), as well as the lowest pyrethrin II (PII) content. In contrast, the populations from Biokovo and Pelješac represented pyrethrin profiles with the lowest content of total pyrethrin, PI and PI/PII ratio. The Biokovo population also had the highest PII content (43.18% on average), while the Pelješac population had the highest jasmolin I (JI) and jasmolin II (JII) content. Four different chemotypes were determined by cluster analysis. Chemotype P1 is the most promising for future breeding programs and is characterized by the highest total pyrethrin content, PI content and PI/PII ratio, as important measures of insecticidal activity. Correlation analysis of each pyrethrin compound with 25 environmental variables and Principal Component Analysis (PCA) were carried out and the importance of optimum temperature and precipitation on pyrethrin quantity and quality was suggested. Total pyrethrin content was significantly correlated with six temperature and five precipitation parameters. Pyrethrin I, PII and cinerin II (CII) were significantly correlated mainly with temperature parameters; JII and cinerin I (CI) with precipitation parameters, while JI was correlated with temperature range and precipitation parameters. The mountainous Biokovo population was an outlier in the PCA analysis, mainly due to the extremely low values of temperature parameters at a higher altitude. Precipitation variables separated the central Adriatic islands inhabiting drier habitats from populations inhabiting habitats with greater precipitation. The high-resolution data from this study provide the opportunity for individual-based selection for breeding plants with the best pyrethrin profiles, as well as for increased adaptation to broader climatic conditions.
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•High intra- and interpopulation chemical diversity exists in pyrethrum populations.•Four distinct pyrethrin chemotypes were observed varying in insecticidal potential.•The individual-based selection of pyrethrin profiles for breeding is proposed.•Temperature and precipitation are correlated with pyrethrin content and composition.
Pyrethrin is a potent biopesticide, a natural mixture of six compounds (pyrethrin I and II, cinerin I and II, and jasmolin I and II), biosynthesized in plants of Dalmatian pyrethrum (
Tanacetum ...cinerariifolium
(Trevir.) Sch. Bip.), a species endemic to the eastern Adriatic coast, but grown worldwide. Not many known natural insecticides encompass such superior qualities as pyrethrin—very high efficacy against a broad spectrum of pests in combination with minor adverse effects on human health and the environment. In previous decades, pyrethrin was largely replaced by its synthetic derivatives, pyrethroids. However, due to their harmful effects on various species and ecosystems, the use of pyrethrin should again take the lead. This review summarizes one century (1920–2020) of research on the properties and use of pyrethrum as a source of pyrethrins. The primary focus is on presenting its current advantages and disadvantages, toxicity on target and non-target species, biosynthesis, factors that influence the pyrethrins content in pyrethrum, comparison of different methods of their extraction and determination; as well as its production potential and development of new products. The final goal is to present possible approaches to improve and enhance the use of this highly effective but still underused phytochemical insecticide with unique properties.
a In the natural pesticides known as pyrethrins, which are esters produced in flowers of Tanacetum cinerariifolium (Asteraceae), the monoterpenoid acyl moiety is pyrethric acid or chrysanthemic acid.
...We show here that pyrethric acid is produced from chrysanthemol in six steps catalyzed by four enzymes, the first five steps occurring in the trichomes covering the ovaries and the last one occurring inside the ovary tissues.
Three steps involve the successive oxidation of carbon 10 (C10) to a carboxylic group by TcCHH, a cytochrome P450 oxidoreductase. Two other steps involve the successive oxidation of the hydroxylated carbon 1 to give a carboxylic group by TcADH2 and TcALDH1, the same enzymes that catalyze these reactions in the formation of chrysanthemic acid. The ultimate result of the actions of these three enzymes is the formation of 10-carboxychrysanthemic acid in the trichomes. Finally, the carboxyl group at C10 is methylated by TcCCMT, a member of the SABATH methyltransferase family, to give pyrethric acid. This reaction occurs mostly in the ovaries.
a Expression in N. benthamiana plants of all four genes encoding aforementioned enzymes, together with TcCDS, a gene that encodes an enzyme that catalyzes the formation of chrysanthemol, led to the production of pyrethric acid.
Researchers have established that (+)‐7‐iso‐jasmonic acid ((+)‐7‐iso‐JA) is an intermediate in the production of cis‐jasmone (CJ); however, the biosynthetic pathway of CJ has not been fully ...described. Previous reports stated that CJ, a substructure of pyrethrin II produced by pyrethrum (Tanacetum cinerariifolium), is not biosynthesized through this biosynthetic pathway. To clarify the ambiguity, stable isotope‐labelled jasmonates were synthesized, and compounds were applied to apple mint (Mentha suaveolens) via air propagation. The results showed that cis‐jasmone is not generated from intermediate (+)‐7‐iso‐JA, and (+)‐7‐iso‐JA is not produced from 3,7‐dideydro‐JA (3,7‐ddh‐JA); however, 3,7‐didehydro‐JA and 4,5‐didehydro‐7‐iso‐JA were converted into CJ and JA, respectively.
GC MS/MS experiments using deuterium‐labelled methyl jasmonate, methyl 4,5‐didehydro‐jasmonate, and methyl 3,7‐didehydro‐jasmonate. The compounds were provided by air propagation, and the biosynthetic pathways identified to produce jasmonic acid and cis‐jasmone were separate and independent in Mentha suavelons.
Natural pyrethrins have high application value, and are widely used as a green pesticide in crop pest prevention and control. Pyrethrins are mainly extracted from the flower heads of
; however, the ...natural content is low. Therefore, it is essential to understand the regulatory mechanisms underlying the synthesis of pyrethrins through identification of key transcription factors. We identified a gene encoding a MYC2-like transcription factor named
from
transcriptome, which is induced by methyl jasmonate. In the present study, we evaluated the regulatory effects and mechanisms of TcbHLH14 using expression analysis, a yeast one-hybrid assay, electrophoretic mobility shift assay, and overexpression/virus-induced gene silencing experiments. We found that TcbHLH14 can directly bind to the cis-elements of the pyrethrins synthesis genes
and
to activate their expression. The transient overexpression of TcbHLH14 enhanced expression of the
and
genes. Conversely, transient silencing of
downregulated the expression of
and
and reduced the content of pyrethrins. In summary, these results indicate that the potential application of TcbHLH14 in improving the germplasm resources and provide a new insight into the regulatory network of pyrethrins biosynthesis of
to further inform the development of engineering strategies for increasing pyrethrins contents.
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