anthocyanin pigments
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Redressing the roles of anthocyanin pigments in vegetative and reproductive organs
<p>Anthocyanin pigments are common in both reproductive and vegetative organs in plants, yet their functional significance is not entirely understood. While communicative functions have received considerable attention in reproductive organs and the role of anthocyanic colouration in frugivore and pollinator attraction is well understood, it has also been suggested that anthocyanins provide a communicative function in vegetative organs i.e. it may be that anthocyanic colouration in leaves deters herbivores by signalling a plant’s defensive investment. Conversely, there is evidence that anthocyanins in vegetative organs perform a number of physiological functions such as photoprotection and mitigation of various environmental stressors. While these physiological roles have received considerable attention in leaves, little is known about the applicability of these functions to anthocyanins in reproductive organs. There is evidently a gap in anthocyanin research; no study has provided unequivocal support for a communicative function for anthocyanins in vegetative organs and no study has shown that anthocyanins perform a physiological function in the reproductive organs in any species other than domesticated crop plants. To address this imbalance in anthocyanin research my thesis tested for a signalling role in vegetative organs, and then investigated a physiological role for anthocyanins in reproductive organs. In chapter two, I hypothesised that for Pseudowintera colorata, red (anthocyanic) leaf margins reduce leaf herbivory by signalling to herbivorous insects the presence of increased chemical defences. Using a natural population of P. colorata, I showed that leaves with the wider red margins contained higher concentrations of anthocyanins and polygodial, a sesquiterpene dialdehyde with known anti-feedant properties, and incurred less natural herbivory. Additionally, laboratory feeding trials involving a natural P. colorata herbivore, Ctenopseustis obliquana larvae, showed a preference for green-margined leaves over red, but only when feeding trials were conducted under light regimes which allowed discrimination of leaf colour. Collectively, my data show that red leaf margins provide a reliable and effective visual signal of chemical defence in P. colorata. Moreover, C. obliquana larvae apparently perceive and respond to the colour of leaf margins, rather than to olfactory cues. My study is therefore the first to provide direct support for a communicative function for anthocyanins in vegetative organs. In peduncles, rays and pedicels, the sterile components of an inflorescence, anthocyanin accumulation has exclusively been considered an adaptation to promote frugivore visitation; however, anthocyanins may instead be produced to mitigate light stress. In chapter three, I tested the requirements of a physiological function, that anthocyanins provide photoprotection for Sambucus nigra peduncles which turn red prior to fruit maturation. I found that accumulation of red pigmentation required exposure to full sunlight and that anthocyanins significantly reduced the quantity of green light that would normally reach chlorenchyma in the peduncle. Under saturating white light, red peduncles maintained higher quantum efficiencies of photosystem II compared to green peduncles, and red portions of peduncle recovered from photoinactivation more quickly than did green portions. My data are, therefore, the first to show that anthocyanins perform a physiological function in the reproductive organs of a naturalised species. In chapter four, I hypothesised that anthocyanin accumulation in senescing Sambucus canadensis peduncles prolongs senescence and enhances nitrogen resorption. Red peduncles possessed several traits indicative of a prolonged senescence; their rates of chlorophyll and xanthophyll decline were lower, while tensile strength and elasticity were higher than for green peduncles. Red peduncles were also less susceptible to photoinactivation than the green ones at the later stages of senescence. However, manipulating green peduncles with light filters possessing transmittance properties comparable to an anthocyanic tissue layer did not increase peduncle longevity or nitrogen resorption. I concluded that like senescing leaves, red peduncles display many characteristics indicative of a prolonged senescence, but I am unable to attribute this benefit to the presence of anthocyanins. This thesis provides a significant contribution to our understanding of the role of anthocyanins in plants in two ways: it is the first to directly demonstrate that anthocyanins perform a communicative function in vegetative organs, and is the first to show for a naturalised (non-cultivar) species, that anthocyanins perform a physiological function in reproductive organs.</p>
<p>Anthocyanin pigments are common in both reproductive and vegetative organs in plants, yet their functional significance is not entirely understood. While communicative functions have received considerable attention in reproductive organs and the role of anthocyanic colouration in frugivore and pollinator attraction is well understood, it has also been suggested that anthocyanins provide a communicative function in vegetative organs i.e. it may be that anthocyanic colouration in leaves deters herbivores by signalling a plant’s defensive investment. Conversely, there is evidence that anthocyanins in vegetative organs perform a number of physiological functions such as photoprotection and mitigation of various environmental stressors. While these physiological roles have received considerable attention in leaves, little is known about the applicability of these functions to anthocyanins in reproductive organs. There is evidently a gap in anthocyanin research; no study has provided unequivocal support for a communicative function for anthocyanins in vegetative organs and no study has shown that anthocyanins perform a physiological function in the reproductive organs in any species other than domesticated crop plants. To address this imbalance in anthocyanin research my thesis tested for a signalling role in vegetative organs, and then investigated a physiological role for anthocyanins in reproductive organs. In chapter two, I hypothesised that for Pseudowintera colorata, red (anthocyanic) leaf margins reduce leaf herbivory by signalling to herbivorous insects the presence of increased chemical defences. Using a natural population of P. colorata, I showed that leaves with the wider red margins contained higher concentrations of anthocyanins and polygodial, a sesquiterpene dialdehyde with known anti-feedant properties, and incurred less natural herbivory. Additionally, laboratory feeding trials involving a natural P. colorata herbivore, Ctenopseustis obliquana larvae, showed a preference for green-margined leaves over red, but only when feeding trials were conducted under light regimes which allowed discrimination of leaf colour. Collectively, my data show that red leaf margins provide a reliable and effective visual signal of chemical defence in P. colorata. Moreover, C. obliquana larvae apparently perceive and respond to the colour of leaf margins, rather than to olfactory cues. My study is therefore the first to provide direct support for a communicative function for anthocyanins in vegetative organs. In peduncles, rays and pedicels, the sterile components of an inflorescence, anthocyanin accumulation has exclusively been considered an adaptation to promote frugivore visitation; however, anthocyanins may instead be produced to mitigate light stress. In chapter three, I tested the requirements of a physiological function, that anthocyanins provide photoprotection for Sambucus nigra peduncles which turn red prior to fruit maturation. I found that accumulation of red pigmentation required exposure to full sunlight and that anthocyanins significantly reduced the quantity of green light that would normally reach chlorenchyma in the peduncle. Under saturating white light, red peduncles maintained higher quantum efficiencies of photosystem II compared to green peduncles, and red portions of peduncle recovered from photoinactivation more quickly than did green portions. My data are, therefore, the first to show that anthocyanins perform a physiological function in the reproductive organs of a naturalised species. In chapter four, I hypothesised that anthocyanin accumulation in senescing Sambucus canadensis peduncles prolongs senescence and enhances nitrogen resorption. Red peduncles possessed several traits indicative of a prolonged senescence; their rates of chlorophyll and xanthophyll decline were lower, while tensile strength and elasticity were higher than for green peduncles. Red peduncles were also less susceptible to photoinactivation than the green ones at the later stages of senescence. However, manipulating green peduncles with light filters possessing transmittance properties comparable to an anthocyanic tissue layer did not increase peduncle longevity or nitrogen resorption. I concluded that like senescing leaves, red peduncles display many characteristics indicative of a prolonged senescence, but I am unable to attribute this benefit to the presence of anthocyanins. This thesis provides a significant contribution to our understanding of the role of anthocyanins in plants in two ways: it is the first to directly demonstrate that anthocyanins perform a communicative function in vegetative organs, and is the first to show for a naturalised (non-cultivar) species, that anthocyanins perform a physiological function in reproductive organs.</p>
<p>Anthocyanin pigments are synthesised in the leaves of many plants, however the adaptive significance of these pigments is not entirely understood. It has been postulated that their red colours may function as visual signals through coevolution between herbivorous insects and their host tree species, though the hypothesis lacks solid empirical evidence. I investigated the leaf signalling hypothesis using Pseudowintera colorata, focusing on five areas: 1) I exploited the natural polymorphism in leaf colour of P. colorata to test the predictions that (i) bright leaf colour is a reliable signal of a plant’s defensive commitment; (ii) insects in the field avoid trees that are brightly coloured; and (iii) the trees with the brightest leaves will have higher fitness. Relative to green leaves, redder foliage contained higher concentrations of polygodial, a sesquiterpene dialdehyde known to have strong antifeedant properties, and incurred less insect feeding damage. Redder trees hosted fewer Ctenopseustis spp. leafroller larvae than neighbouring matched green trees. Contrary to the predictions of the leaf signalling hypothesis, there was no difference in any of the measured fitness parameters between red and green trees, indicating that the leaf colour polymorphism in P. colorata is stable. 2) Many insects are sensitive to volatile organic compounds (VOCs), however the role of VOCs in plant-herbivore signalling has not been investigated. I analysed VOCs released from undamaged, herbivore- and mechanically-damaged red and green leaves of P. colorata, and the olfactory preferences of brownheaded leafroller (C. obliquana) larvae. While the VOC profiles of browsed and unbrowsed leaves were statistically distinguishable, the VOC profiles released from intact, herbivore-, and mechanically-damaged P. colorata leaves did not reliably identify leaf colour. Moreover, naïve and experienced C. obliquana larvae displayed no preference for the volatiles from mechanically-damaged red or green leaves. Therefore, I concluded that VOC compounds are not likely to play a large role in mediating insect herbivore-plant interactions in P. colorata. 3) Studies of leaf signalling rarely consider the influence of the light-absorbing properties of non-green pigments upon photosynthesis. I compared the photosynthetic and photoinhibitory responses of red and green leaves from matched, neighbouring pairs of P. colorata of contrasting colour. Redder P. colorata leaves in the field had a lower maximum photosynthetic assimilation rate than matched green leaves from neighbouring trees. However, I was unable to detect any measurable advantage in terms of photoprotection in the red P. colorata leaves as indicated by chlorophyll fluorescence profiles. My results indicate that the presence of anthocyanin pigments within non-senescing leaves may impose a slight photosynthetic cost to the plant. 4) I used literature searches, field surveys and laboratory bioassays to identify which invertebrate herbivores are most likely to participate in leaf-signalling interactions with P. colorata. Feeding preference bioassays showed that brownheaded leafrollers (C. obliquana and C. herana) and Auckland tree weta (Hemideina thoracica) preferentially consumed leaf material from green than red P. colorata leaves. Results from these bioassays, combined with my field surveys suggest that Ctenopseustis spp. leafroller larvae are the most likely coevolution partners for P. colorata. 5) There is a well-established link between nitrogen deficiency and leaf reddening. Additionally, leaf nutrients can influence foraging behaviour and performance of insect herbivores. I measured N and C contents of leaves from neighbouring matched pairs of red and green P. colorata. There were no significant differences in the amounts of, or ratio between, N and C between matched red and green leaves. This result indicates that differences in colour and herbivory among P. colorata leaves are not attributable to differences in leaf nutrients. Taken together, my results suggest that foliar anthocyanins in P. colorata do function as visual signals, however their effect on herbivory is small. Additionally, interindividual variation in non-senescing leaf colour in P. colorata may be stable due to a trade off between signalling and photosynthesis. Discussions of leaf signalling need to follow the examples of other fields studying the interactions between plants and insects and move from overly simple models to those that incorporate more of the complexity that is observed in the natural world.</p>
<p>Anthocyanin pigments are synthesised in the leaves of many plants, however the adaptive significance of these pigments is not entirely understood. It has been postulated that their red colours may function as visual signals through coevolution between herbivorous insects and their host tree species, though the hypothesis lacks solid empirical evidence. I investigated the leaf signalling hypothesis using Pseudowintera colorata, focusing on five areas: 1) I exploited the natural polymorphism in leaf colour of P. colorata to test the predictions that (i) bright leaf colour is a reliable signal of a plant’s defensive commitment; (ii) insects in the field avoid trees that are brightly coloured; and (iii) the trees with the brightest leaves will have higher fitness. Relative to green leaves, redder foliage contained higher concentrations of polygodial, a sesquiterpene dialdehyde known to have strong antifeedant properties, and incurred less insect feeding damage. Redder trees hosted fewer Ctenopseustis spp. leafroller larvae than neighbouring matched green trees. Contrary to the predictions of the leaf signalling hypothesis, there was no difference in any of the measured fitness parameters between red and green trees, indicating that the leaf colour polymorphism in P. colorata is stable. 2) Many insects are sensitive to volatile organic compounds (VOCs), however the role of VOCs in plant-herbivore signalling has not been investigated. I analysed VOCs released from undamaged, herbivore- and mechanically-damaged red and green leaves of P. colorata, and the olfactory preferences of brownheaded leafroller (C. obliquana) larvae. While the VOC profiles of browsed and unbrowsed leaves were statistically distinguishable, the VOC profiles released from intact, herbivore-, and mechanically-damaged P. colorata leaves did not reliably identify leaf colour. Moreover, naïve and experienced C. obliquana larvae displayed no preference for the volatiles from mechanically-damaged red or green leaves. Therefore, I concluded that VOC compounds are not likely to play a large role in mediating insect herbivore-plant interactions in P. colorata. 3) Studies of leaf signalling rarely consider the influence of the light-absorbing properties of non-green pigments upon photosynthesis. I compared the photosynthetic and photoinhibitory responses of red and green leaves from matched, neighbouring pairs of P. colorata of contrasting colour. Redder P. colorata leaves in the field had a lower maximum photosynthetic assimilation rate than matched green leaves from neighbouring trees. However, I was unable to detect any measurable advantage in terms of photoprotection in the red P. colorata leaves as indicated by chlorophyll fluorescence profiles. My results indicate that the presence of anthocyanin pigments within non-senescing leaves may impose a slight photosynthetic cost to the plant. 4) I used literature searches, field surveys and laboratory bioassays to identify which invertebrate herbivores are most likely to participate in leaf-signalling interactions with P. colorata. Feeding preference bioassays showed that brownheaded leafrollers (C. obliquana and C. herana) and Auckland tree weta (Hemideina thoracica) preferentially consumed leaf material from green than red P. colorata leaves. Results from these bioassays, combined with my field surveys suggest that Ctenopseustis spp. leafroller larvae are the most likely coevolution partners for P. colorata. 5) There is a well-established link between nitrogen deficiency and leaf reddening. Additionally, leaf nutrients can influence foraging behaviour and performance of insect herbivores. I measured N and C contents of leaves from neighbouring matched pairs of red and green P. colorata. There were no significant differences in the amounts of, or ratio between, N and C between matched red and green leaves. This result indicates that differences in colour and herbivory among P. colorata leaves are not attributable to differences in leaf nutrients. Taken together, my results suggest that foliar anthocyanins in P. colorata do function as visual signals, however their effect on herbivory is small. Additionally, interindividual variation in non-senescing leaf colour in P. colorata may be stable due to a trade off between signalling and photosynthesis. Discussions of leaf signalling need to follow the examples of other fields studying the interactions between plants and insects and move from overly simple models to those that incorporate more of the complexity that is observed in the natural world.</p>
Introduction. Smart food packaging that alerts consumers to spoilt food by changing color is based on affordable and biodegradable raw materials. The research objective was to develop films from anionic polysaccharides and anthocyanin pigment that can be used as a freshness indicator of minced fish. Study objects and methods. The study featured frozen black currant berries (Ríbes nígrum), polysaccharide-based anthocyanin films, and minced fish. Extracts of anthocyanin pigment and films based on agar, kappa-carrageenan, chitosan, starch, and anthocyanin pigments were analyzed by IR spectroscopy. Results and its discussion. Anionic polysaccharides, i.e. agar and kappa-carrageenan, demonstrated good film-forming properties. Films based on 1.5% agar and 2% kappa-carrageenan showed elasticity, resilience, plasticity, and sufficient resistance to mechanical deformation. Neutral polysaccharide starch and cationic polysaccharide chitosan appeared to have no such qualities. An IR spectral analysis revealed chemical interactions between polysaccharide and anthocyanin molecules. It indicated the electrostatic nature of the polyelectrolyte complexes of the anthocyanin pigment with anionic polysaccharides. A film based on 1.5% agar fortified with anthocyanin pigment was used as a test-system for analyzing the quality of fish. The minced fish samples were wrapped in the anthocyanin film and left for 2–7 min to register the color change of the film. When the anthocyanin film came in contact with fresh fish, the color of the film did not change even after prolonged contact. When the film came into contact with spoilt fish, the color of the film began to change after 2 min of contact. When the contact time reached 7 min, the film turned blue. Conclusion. The type of polysaccharide and the interaction between polysaccharides and anthocyanin pigment had a significant effect on film formation. Anionic polysaccharides demonstrated the best results. Electrostatic interactions between anionic polysaccharides and anthocyanin pigments produced stable polyelectrolyte complexes. The new smart films were able to determine the quality of minced fish.
Choices of blue food colourants are extremely limited, with only two options in the USA, synthetic blue no. 1 and no. 2, and a third available in Europe, patent blue V. The food industry is investing heavily in finding naturally derived replacements, with limited success to date. Here, we review the complex and multifold mechanisms whereby blue pigmentation by anthocyanins is achieved in nature. Our aim is to explain how structure determines the functionality of anthocyanin pigments, particularly their colour and their stability. Where possible, we describe the impact of progressive decorations on colour and stability, drawn from extensive but diverse physico-chemical studies. We also consider briefly how this understanding could be harnessed to develop blue food colourants on the basis of the understanding of how anthocyanins create blues in nature.
Abstract This study aims to identify anthocyanin pigments in Sudanese roselle and examine their inhibitory activity toward xanthine oxidase (XO) enzyme via in silico docking approach. A number of four samples of Sudanese roselle (red and white) from different regions of Sudan were investigated by high sensitive technique, i.e. LC-MS to identify anthocyanins. Four anthocyanins were identified in all samples; delphinidin-3-glucoside (Dp-3-glu), cyanidin-3-sambubioside (Cy-3-sam), pelargonidin chloride (Pg Chloride), and petuinidin-3-glucoside (Pt-3-glu); in addition to one flavanol; gossypetin (Goss). The anthocyanins of the white samples are suggested to be presented in the yellowish or colorless pseudo base structures. The identified anthocyanins were tested against the inhibition toward xanthine oxidase via molecular docking. All anthocyanins were found to be excellent XO inhibitors superior to the most recent commercially used hyperuricemia drug; i.e. topiroxostat. The binding energies of the complexes (ligand-XO) are lower than the energy of the topiroxostat-XO complex. The binding energies order is: pt-3- dp-3-glu > cy-3-sam > goss > pg chloride. According to our investigation, roselle anthocyanins are considered as good potential future XO-inhibitors drugs; and promising candidates to treat several related diseases.
Genetically modified carnation (Dianthus caryophyllus L.) line IFD-25958-3 with product name Moonberry™, expresses three introduced traits. The dfr gene from Petunia x hybrida and the f3′5′h gene from Viola hortensis, coding for dihydroflavonol 4-reductase (DFR) and flavonoid 3′,5′-hydroxylase (F3′5′H), respectively, lead to the biosynthesis of anthocyanin pigments, which confer the desired violet/blue colour to the flowers. A mutated als gene (SuRB) from Nicotiana tabacum has also been inserted, coding for an acetolactate synthase (ALS) variant protein and thereby conferring tolerance to the active, ALS-inhibiting, herbicidal substances chlorimuron, thifensulfuron and sulfonylureas, used to facilitate the selection of GM shoots during genetic transformation. Of note, carnation Moonberry IFD25958-3 contained a hairpin RNA interference (RNAi) gene, which down-regulates endogenous dfr. Bioinformatics analyses of the inserted DNA and flanking sequences in carnation Moonberry IFD-25958-3 have not indicated a potential production of putative harmful proteins or polypeptides caused by the genetic modification. Genomic stability of the functional insert and consistent expression of the dfr and f3′5′h genes, have been shown over several generations of carnation Moonberry IFD-25958-3. Data reported from several field trials show that carnation Moonberry IFD-25958-3 petals contain higher levels of the anthocyanins delphinidin and cyanidin, and lower levels of pelargonidin compared to the non-GM (conventional) carnation counterpart Cerise Westpearl (CW). Other morphological traits were reported and along with differing petal colour, carnation Moonberry IFD-25958-3 differed significantly in nine traits compared to conventional carnation counterpart CW. Aqueous extracts from leaves or petals showed no mutagenic activity in vitro. ALS, DFR, and F3’5’H proteins do not show sequence resemblance to known toxins or IgE-dependent allergens, nor have they been reported to be toxic to animals or cause IgE-mediated allergic reactions. The anthocyanins delphinidin and cyanidin are present in numerous foods and are also approved food additives. Carnations are cultivated in Norway, but since 1) the intended uses includes import of cut flowers for ornamental use only, 2) the spread and viability of pollen from the cut flowers is low, 3) seed formation in cut flowers is unlikely to occur, and 4) spread of inserted genes to target or non-target organisms is either unlikely to occur or is not of biological relevance, the VKM GMO Panel does not consider that carnation Moonberry IFD-25958-3 represents an environmental risk in Norway. Considering that carnation Moonberry IFD-25958-3 is not intended for cultivation or use as food or feed, the VKM GMO Panel considers that comparative analysis of the newly synthesised anthocyanin pigments delphinidin, cyanidin and pelargonidin in its petals is sufficient for the risk assessment. The reported morphological differences between Moonberry IFD-25958-3 and its conventional carnation counterpart Cerise Westpearl (CW) do not raise safety concerns. It is unlikely that the DFR, F3’5’H or ALS proteins, or the delphinidin or cyanidin pigments, will introduce a toxic or allergenic potential in Moonberry IFD-25958-3. Based on current knowledge and information supplied by the applicant, and considering the intended use, which excludes cultivation and use as food and feed, the VKM GMO Panel concludes that Moonberry IFD-25958-3 is as safe as its conventional counterpart CW. Based on the current knowledge and considering its import, distribution and intended use as cut ornamental flowers, the VKM GMO Panel concludes that it is unlikely that carnation Moonberry IFD-25958-3 will have any adverse effects on the biotic or abiotic environment in Norway.
