The whitefly, Bemisia tabaci, is a destructive and invasive pest of many horticultural plants including poinsettia (Euphorbia pulcherrima). Outbreaks of B. tabaci cause serious damage by direct ...feeding on phloem sap, and spreading 100+ plant viruses to crops. Bemisia tabaci were observed more frequently on green than red poinsettia leaves, and the factors responsible for this are unknown. Here, we investigated the development rate, survivorship, fecundity of B. tabaci feeding on green versus red leaves, as well as the leaves' volatiles, trichome density, anthocyanin content, soluble sugars, and free amino acids. Compared to red leaves, B. tabaci on green leaves showed increased fecundity, a higher female sex ratio, and survival rate. The green color alone was more attractive to B. tabaci than red. Red leaves of poinsettia contained more phenol, and panaginsene in their volatiles. Alpha-copaene and caryophyllene were more abundant in the volatiles of poinsettia green leaves. Leaf trichome density, soluble sugars and free amino acids were higher in green than red leaves of poinsettia, anthocyanin was lower in green than red leaves. Overall, green leaves of poinsettia were more susceptible and attractive to B. tabaci. The morphological and chemical variation between red and green leaves also differed; further investigation may reveal how these traits affect B. tabaci's responses.
The range of floral colors is determined by the type of plant pigment accumulated by the plant. Anthocyanins are the most common flavonoid pigments in angiosperms; they provide a wide range of ...visible colors from red-magenta to blue-purple, products of cyanidin and delphinidin biosynthesis, respectively. For the floriculture industry, floral color is one of the most important ornamental characteristics for the development of new commercial varieties; however, most plant species are restricted to a certain color spectrum, limited by their own genetics. In fact, many ornamental crops lack bluish varieties due to the lack of activity of essential biosynthetic enzymes for the accumulation of delphinidin. An example is the poinsettia (
Willd. ex Klotzsch), the ornamental plant symbol of Christmas and native to Mexico. Its popularity is the result of the variety of colors displayed by its bracts, a kind of modified leaves that accumulate reddish pigments based mainly on cyanidin and, to a lesser extent, on pelargonidin. The commercial success of this plant lies in the development of new varieties and, although consumers like the typical red color, they are also looking for poinsettias with new and innovative colors. Previous research has demonstrated the possibility of manipulating flower color through metabolic engineering of the anthocyanin biosynthesis pathway and plant tissue culture in different ornamental plant species. For example, transgenic cultivars of flowers such as roses, carnations or chrysanthemums owe their attractive bluish colors to a high and exclusive accumulation of delphinidin. Here, we discuss the possibilities of genetic engineering of the anthocyanin biosynthetic pathway in
through the introduction of one or more foreign delphinidin biosynthetic genes under the transcriptional control of a pathway-specific promoter, and the genome editing possibilities as an alternative tool to modify the color of the bracts. In addition, some other approaches such as the appropriate selection of the cultivars that presented the most suitable intracellular conditions to accumulate delphinidin, as well as the incorporation of genes encoding anthocyanin-modifying enzymes or transcription factors to favor the bluish pigmentation of the flowers are also revised.
•Transcriptomes of green and red-turning bracts of poinsettia were analysed.•The contents of flavonoids in poinsettia bracts were monitored.•Inhibition of DFR leads to produce byproducts rather than ...anthocyanins.•DFR content was increased under short-day conditions in poinsettia bracts.•DFR contributes to anthocyanin accumulation in red-turning bracts of poinsettia.
Poinsettia (Euphorbia pulcherrima, Willd. ex Klotzsch) originated in Mexico is an important ornamental tree in all over the world because its bract color can change from green to red under short-day conditions. In view of this, poinsettia not only has high ornamental value but also is an important model plant in studies on anthocyanin metabolism regulated by photoperiod. In this research, we compared the content of metabolic products in anthocyanin biosynthesis pathway and transcriptome sequencing data between green and red-turning bracts of poinsettia to clarify the mechanism of color change. The results of metabolic product analysis suggested that far downstream genes such as dihydroflavonol 4-reductase (DFR) gene in anthocyanin biosynthesis pathway could be inhibited in green bracts. A total of 91,917 uni-transcripts were identified through transcriptome sequencing. Seventy-two uni-transcripts were assigned to flavonoid biosynthesis pathways. Through a correlation analysis of gene expression profiles and color compound contents, DFR was taken into account as a candidate gene promoting anthocyanin accumulation in poinsettia bracts under short-day conditions. Transgenic research showed that overexpression of poinsettia DFR significantly increased the anthocyanin content in Arabidopsis (Arabidopsis thaliana). Based on these results, this research identified DFR as a promoter of anthocyanin accumulation in poinsettia bracts under short-day conditions. Moreover, the results of this research will shed light on elucidation of anthocyanin biosynthesis mechanism of plants and provide candidate genes for genetic improvement on poinsettia.
Background: Euphorbia pulcherrima is highly ornamental value of poinsettia flower, which posses colorful bracts and low temperature resistant leave. Its embryos or adventitious buds were cultivated ...mainly from stems, petioles and tender buds. The cultivation of seedlings is studied firstly for improving the quality of Poinsettia.
Methods: A rapid and reproducible regeneration system of leaves and stems with buds has been established. There is a comparative analysis of the results of tissue culture of different varieties of Poinsettia.
Result: The best medium component of hormones about leaf callus of poinsettia inducing cluster buds formation comprise 6-BA 1.0 mg/L, KT 0.4 mg/L, NAA 0.1 mg/L and 2,4-D 0.05 mg/L. Its medium component inducing cluster buds proliferation include 6-BA 1.2 mg/L and NAA 0.05 mg/L. The medium component about stem with bud inducing cluster buds to germinate comprise 6-BA 1.5 mg/L and NAA 0.1 mg/L. Its medium component inducing cluster buds proliferation include 6-BA 1.0 mg/L and NAA 0.05 mg/L. The different hormones and different addition level of Ac have effect on the length of the root and quantity of the first level root and the second level root.
Commercially available poinsettia (Euphorbia pulcherrima) varieties prevalently accumulate cyanidin derivatives and show intense red coloration. Orange-red bract color is less common. We investigated ...four cultivars displaying four different red hues with respect to selected enzymes and genes of the anthocyanin pathway, putatively determining the color hue.
Red hues correlated with anthocyanin composition and concentration and showed common dark red coloration in cultivars 'Christmas Beauty' and 'Christmas Feeling' where cyanidin derivatives were prevalent. In contrast, orange-red bract color is based on the prevalent presence of pelargonidin derivatives that comprised 85% of the total anthocyanin content in cv. 'Premium Red' and 96% in cv. 'Harvest Orange' (synonym: 'Orange Spice'). cDNA clones of flavonoid 3'-hydroxylase (F3'H) and dihydroflavonol 4-reductase (DFR) were isolated from the four varieties, and functional activity and substrate specificity of the corresponding recombinant enzymes were studied. Kinetic studies demonstrated that poinsettia DFRs prefer dihydromyricetin and dihydroquercetin over dihydrokaempferol, and thus, favor the formation of cyanidin over pelargonidin. Whereas the F3'H cDNA clones of cultivars 'Christmas Beauty', 'Christmas Feeling', and 'Premium Red' encoded functionally active enzymes, the F3'H cDNA clone of cv. 'Harvest Orange' contained an insertion of 28 bases, which is partly a duplication of 20 bases found close to the insertion site. This causes a frameshift mutation with a premature stop codon after nucleotide 132 and, therefore, a non-functional enzyme. Heterozygosity of the F3'H was demonstrated in this cultivar, but only the mutated allele was expressed in the bracts. No correlation between F3'H-expression and the color hue could be observed in the four species.
Rare orange-red poinsettia hues caused by pelargonidin based anthocyanins can be achieved by different mechanisms. F3'H is a critical step in the establishment of orange red poinsettia color. Although poinsettia DFR shows a low substrate specificity for dihydrokaempferol, sufficient precursor for pelargonidin formation is available in planta, in the absence of F3'H activity.
To investigate the herbicidal potential of 2,5-diketopiperazines (2,5-DKPs), we applied a known protocol to produce a series of 2,5-DKPs through intramolecular N-alkylation of Ugi adducts. However, ...the method was not successful for the cyclization of adducts presenting aromatic rings with some substituents at the ortho position. Results from DFT calculations showed that the presence of voluminous groups at the ortho position of a benzene ring results in destabilization of the transition structure. Lower activation enthalpies for the SN2-type cyclization of Ugi adducts were obtained when bromine, instead of a chlorine anion, is the leaving group, indicating that the activation enthalpy for the cyclization step controls the formation of the 2,5-DKP. Some Ugi adducts and 2,5-DKPs formed crystals with suitable qualities for single-crystal X-ray diffraction data collection. Phytotoxic damage of some 2,5-DKPs on leaves of the weed Euphorbia heterophylla did not differ from those caused by the commercial herbicide diquat.
Whether increased natural enemy density or adding a second natural enemy species will provide superior pest suppression in greenhouse augmentative biological control is unknown for many commercially ...available natural enemy species. In this study, we use sweetpotato whiteflies, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), on poinsettias, Euphorbia pulcherrima Willd. ex Klotzsch (Malpighiales: Euphorbiaceae), to determine whether adding Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) to Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae) is better for B. tabaci suppression compared with either natural enemy alone, both with and without challenges with whitefly immigration or delayed natural enemy releases. The number of whiteflies on caged poinsettias treated with different natural enemy release rates (single or double rate), natural enemy species (one or two species), natural enemy delayed release (weeks 4 and 8), and whitefly immigration treatments (introduced at week 4 or week 8) was censused biweekly for 16 wk. Both species used in combination provided similar or better suppression of whiteflies compared with either natural enemy alone. Both species combined also provided superior suppression of whiteflies when challenged with whitefly immigration or delays in natural enemy releases compared with E. eremicus alone. Whitefly immigration or delays in E. eremicus releases did not increase whitefly populations, suggesting that suppression of whiteflies by E. eremicus alone is relatively robust. This study found no evidence for negative interactions between E. eremicus and A. swirskii for suppressing B. tabaci.
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