Reduction In Carotenoid Content Research Articles

Integrated transcriptomics and metabolomics analyses of the effects of bagging treatment on carotenoid biosynthesis and regulation of Areca catechu L.

Fresh Aareca nut fruit for fresh fruit chewing commonly found in green or dark green hues. Despite its economic significance, there is currently insufficient research on the study of color and luster of areca. And the areca nut fruits after bagging showed obvious color change from green to tender yellow. In the study, we tried to explain this interesting variation in exocarp color. Fruits were bagged (with a double-layered black interior and yellow exterior) 45 days after pollination and subsequently harvested 120 days after pollination. In this study, we examined the the chlorophyll and carotenoid content of pericarp exocarp, integrated transcriptomics and metabolomics to study the effects of bagging on the carotenoid pathway at the molecular level. It was found that the chlorophyll and carotenoid content of bagged areca nut (YP) exocarp was significantly reduced. A total of 21 differentially expressed metabolites (DEMs) and 1784 differentially expressed genes (DEGs) were screened by transcriptomics and metabolomics. Three key genes in the carotenoid biosynthesis pathway as candidate genes for qPCR validation by co-analysis, which suggested their role in the regulation of pathways related to crtB, crtZ and CYP707A. We described that light intensity may appear as a main factor influencing the noted shift from green to yellow and the ensuing reduction in carotenoid content after bagging.

Overexpression of PSY1 increases fruit skin and flesh carotenoid content and reveals associated transcription factors in apple (Malus × domestica).

Knowledge of the transcriptional regulation of the carotenoid metabolic pathway is still emerging and here, we have misexpressed a key biosynthetic gene in apple to highlight potential transcriptional regulators of this pathway. We overexpressed phytoene synthase (PSY1), which controls the key rate-limiting biosynthetic step, in apple and analyzed its effects in transgenic fruit skin and flesh using two approaches. Firstly, the effects of PSY overexpression on carotenoid accumulation and gene expression was assessed in fruit at different development stages. Secondly, the effect of light exclusion on PSY1-induced fruit carotenoid accumulation was examined. PSY1 overexpression increased carotenoid content in transgenic fruit skin and flesh, with beta-carotene being the most prevalent carotenoid compound. Light exclusion by fruit bagging reduced carotenoid content overall, but carotenoid content was still higher in bagged PSY fruit than in bagged controls. In tissues overexpressing PSY1, plastids showed accelerated chloroplast to chromoplast transition as well as high fluorescence intensity, consistent with increased number of chromoplasts and carotenoid accumulation. Surprisingly, the expression of other carotenoid pathway genes was elevated in PSY fruit, suggesting a feed-forward regulation of carotenogenesis when this enzyme step is mis-expressed. Transcriptome profiling of fruit flesh identified differentially expressed transcription factors (TFs) that also were co-expressed with carotenoid pathway genes. A comparison of differentially expressed genes from both the developmental series and light exclusion treatment revealed six candidate TFs exhibiting strong correlation with carotenoid accumulation. This combination of physiological, transcriptomic and metabolite data sheds new light on plant carotenogenesis and TFs that may play a role in regulating apple carotenoid biosynthesis.

Soil solution pH can affect the response of the common bean (Phaseolus vulgaris L.) to mesotrione residues

Soil pH can affect the adsorption of mesotrione and exacerbate crop injury under non-acidic conditions. Soil samples collected from the same location were irrigated with water solutions of pH 7.5, 6.5, 5.5, and 4.5 and treated with 72, 36, 24, 18, 9, 4.5, 2.3, and 1.1 g a.i. (active ingredient) of mesotrione/ha. Bean growth was monitored over 28 days. Soil pH solution did not influence the effect of mesotrione on plant fresh weight, while herbicide-induced visual injury and reduction in carotenoid content were significantly mitigated under acidic conditions. The lowest rate (1.1 g a.i./ha) applied in slightly acidic soil (pH 6.5) caused visual injury of 45% 28 days after treatment, while visual injuries on plants grown in soils with pH 4.5 were only 20%. Further, bean plants grown at pH 4.5 showed only 3.3% lower carotenoid content compared to control plants since for those grown in a slightly alkaline environment (pH 7.5) reduction of this pigment was 35.5%. The mean effective dose (ED50 ± standard error) of mesotrione for inhibition of carotenoids were 5.25 ± 0.61 g a.i./ha at pH 7.5, 9.57 ± 0.74 g a.i./ha at pH 6.5, 13.07 ± 0.91 g a.i./ha at pH 5.5, and 14.98 ± 0.94 g a.i./ha at pH 4.5. Results indicate that the common bean is highly susceptible to the presence of mesotrione residue and that this sensitivity strongly depends on soil pH solution.

Morpho-physiological, biochemical, and leaf epidermal responses of Desmostachya bipinnata L. in arid habitats

The response of morpho-physiological and leaf surface attributes along with antioxidant potential of Desmostachya bipinnata L. populations collected from arid regions with 1.7–3.7 soil moisture % and =22.8–49.6 dS m−1 ECe was evaluated for adaptability to aridity. Among soil attributes, soil pH, ECe, moisture content, saturation percentage, organic matter, P, Na+, K+, Ca2+, Mg2+, Cl, NH4-N, NO3-N and plant attributes related to the morphology, physiology, antioxidant potential were studied. With increasing aridity root:shoot length ratio (0.1–0.4 cm) increased while average leaf area (12–4 cm2), shoot biomass (5–0.5 g), and root biomass (0.8–0.1g) decreased significantly. Parallel to that chlorophyll a (1–0.1 mgg−1 fresh weight) degradation was observed along with reduced carotenoid content (0.25–0.05 mgg−1 fresh weight). All other organic osmolytes decreased except for total soluble sugars which increased (0.10–0.15 μmol g−1 fresh weight) as the dryness ratio increased and more activities of the antioxidant enzymes APX (0.5–3.5 units mg pro−1), CAT (0.1–0.8 units mg pro−1), POD (0.02–0.25 units μg pro−1), and SOD (2–7 units mg pro−1) were observed. Among soluble cations, Na+ concentration increased (14–24 mg g−1 dw) in shoot as the aridity increased while shoot K+ (35–15 mgg−1 dw) and Mg2+ concentration decreased in both root and shoot tissues. Ca2+ concentration increased in root while N and P content decreased. In conclusion, aridity reduced overall vegetative growth but enhanced root growth for better absorption of water from the deeper layers with concurrent silica deposition in epidermal layers for controlling water loss.

The impact of life stage and pigment source on the evolution of novel warning signal traits.

Our understanding of how novel warning color traits evolve in natural populations is largely based on studies of reproductive stages and organisms with endogenously produced pigmentation. In these systems, genetic drift is often required for novel alleles to overcome strong purifying selection stemming from frequency‐dependent predation and positive assortative mating. Here, we integrate data from field surveys, predation experiments, population genomics, and phenotypic correlations to explain the origin and maintenance of geographic variation in a diet‐based larval pigmentation trait in the redheaded pine sawfly (Neodiprion lecontei), a pine‐feeding hymenopteran. Although our experiments confirm that N. lecontei larvae are indeed aposematic—and therefore likely to experience frequency‐dependent predation—our genomic data do not support a historical demographic scenario that would have facilitated the spread of an initially deleterious allele via drift. Additionally, significantly elevated differentiation at a known color locus suggests that geographic variation in larval color is currently maintained by selection. Together, these data suggest that the novel white morph likely spread via selection. However, white body color does not enhance aposematic displays, nor is it correlated with enhanced chemical defense or immune function. Instead, the derived white‐bodied morph is disproportionately abundant on a pine species with a reduced carotenoid content relative to other pine hosts, suggesting that bottom‐up selection via host plants may have driven divergence among populations. Overall, our results suggest that life stage and pigment source can have a substantial impact on the evolution of novel warning signals, highlighting the need to investigate diverse aposematic taxa to develop a comprehensive understanding of color variation in nature.

The Photosynthetic Efficiency and Carbohydrates Responses of Six Edamame (Glycine max. L. Merrill) Cultivars under Drought Stress.

Vegetable-type soybean, also known as edamame, was recently introduced to South Africa. However, there is lack of information on its responses to drought. The aim of this study was to investigate the photosynthetic efficiency and carbohydrates responses of six edamame cultivars under drought stress. Photosynthetic efficiency parameters, including chlorophyll fluorescence and stomatal conductance, were determined using non-invasive methods, while pigments were quantified spectrophotometrically. Non-structural carbohydrates were quantified using Megazyme kits. Structural carbohydrates were determined using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Drought stress significantly increased the Fv/Fm and PIabs of AGS429 and UVE17 at pod filling stage. Chlorophyll-a, which was most sensitive to drought, was significantly reduced in AGS429 and UVE17, but chlorophyll-b was relatively stable in all cultivars, except UVE17, which showed a significant decline at flowering stage. AGS354 and AGS429 also showed reduced chlorophyll-b at pod filling. UVE17 showed a significant reduction in carotenoid content and a substantial reduction in stomatal conductance during pod filling. Drought stress during pod filling resulted in a significant increase in the contents of trehalose, sucrose and starch, but glucose was decreased. Chlorophyll-a positively correlated with starch. The FTIR and XRD results suggest that the cell wall of UVE14, followed by UVE8 and AGS429, was the most intact during drought stress. It was concluded that carotenoids, stomatal conductance, starch and hemicellulose could be used as physiological/biochemical indicators of drought tolerance in edamame. This information expands our knowledge of the drought defense responses in edamame, and it is essential for the physiological and biochemical screening of drought tolerance.

Inhibition of 4-HYDROXYPHENYLPYRUVATE DIOXYGENASE expression by brassinosteroid reduces carotenoid accumulation in Arabidopsis.

Unlike the indispensable function of the steroid hormone brassinosteroid (BR) in regulating plant growth and development, the metabolism of secondary metabolites regulated by BR is not well known. Here we show that BR reduces carotenoid accumulation in Arabidopsis seedlings. BR-deficient or BR-insensitive mutants accumulated higher content of carotenoids than wild-type plants, whereas BR treatment reduced carotenoid content. We demonstrated that BR transcriptionally suppresses 4-HYDROXYPHENYLPYRUVATE DIOXYGENASE (HPPD) expression involved in carotenogenesis via plastoquinone production. We found that the expression of HPPD displays an oscillation pattern that is expressed more strongly in dark than in light conditions. Moreover, BR appeared to inhibit HPPD expression more strongly in darkness than in light, leading to suppression of a diurnal oscillation of HPPD expression. BR-responsive transcription factor BRASSINAZOLE RESISTANT 1 (BZR1) directly bound to the promoter of HPPD, and HPPD suppression by BR was increased in the bzr1-1D gain-of-function mutation. Interestingly, dark-induced HPPD expression did not cause carotenoid accumulation, due to down-regulation of other carotenoid biosynthetic genes in the dark. Our results suggest that BR regulates different physiological responses in dark and light through inhibition of HPPD expression.

Foliar application of silver nanoparticles differentially intervenes remediation statuses and oxidative stress indicators in Abelmoschus esculentus planted on gold-mined soil

The study assessed the intervention of foliar application of silver nanoparticles (AgNPs) on heavy metal toxicity and phytoremediation status of Abelmoschus esculentus planted in gold-mined soil. The green synthesized AgNPs absorbed maximally at 425 nm, had an average particle size of 55 ± 2.3 nm and peaks at 3,443 and 1,636 cm−1. A. esculentus seeds were grown in gold-mined soil and its seedlings were wetted with water and different concentrations of AgNPs (0.75, 0.50 and 0.25 mg/mL). Foliar applications of AgNPs significantly improved percentage heavy metal remediation and reduced contamination intensity by 60% and 44%, respectively in A. esculentus. Heavy metals induced oxidative stress in A. esculentus wetted with water which manifested in the reduction of growth performance and photosynthetic pigments by 43% and 15% in that order. Significant overexpression of superoxide dismutase activity and malondialdehyde by 70% and 86%, respectively together with a significant reduction in carotenoid contents and antioxidant activity by 92% and 15%, respectively were obtained for A. esculentus in control. The intervention of foliar application considerably protected A. esculentus with improved physiology, enzymic and non-enzymic antioxidant activities. These results conclude that foliar application AgNPs beneficially mediated toxicities of heavy metals in plants. Novelty statement Gold mining is an economic venture but contamination of ecological matrixes by heavy metals usually accompanies it. Farming on either an active or abandoned gold site can predispose residents to the toxicity of heavy metals. Therefore, remediation before or during cultivation is key to ensuring safety. Silver nanoparticles have proved effective in remediating heavy metals and improving biochemical activities in plants due to their intrinsic properties and adsorptive potentials.

Cloning and characterization ofRARs andRXRs from noble scallopChlamys nobilis, a bivalve rich in carotenoids

The noble scallop Chlamys nobilis that rich in carotenoids is one of the most popular scallop species for aquaculture. Very little is known whether bivalve SRB-like-3 gene expression is regulated by retinoic acid receptor (RAR) and/or retinoic X receptor (RXR). In this study, the full-length cDNA of RAR and RXR genes of C. nobilis was cloned and characterized for the first time, and then, the tissue differential expression of RAR and RXR mRNA in polymorphic C. nobilis was assessed. The roles of RAR and RXR in carotenoid accumulation in C. nobilis were assessed by manipulating the carotenoid content in tissues of C. nobilis via inhibiting the expression of SRB-like-3 gene. The results revealed that two isoforms of RAR (cnRARa (1958 bp/434 aa) and cnRARb (1901 bp/415 aa)) and four RXR isoforms (cnRXRa (1353-bp/450 aa), cnRXRb (1341-bp/446 aa), cnRXRc (1298-bp/436 aa) and cnRXRd (1286-bp/432 aa)) were cloned and characterized from C. nobilis. The reduction of carotenoid content caused by inhibition of SRB-like-3 gene induced the up-regulation of RAR and RXR genes, suggesting that RAR and RXR genes may play a role in the regulation of carotenoid accumulation in haemolymph of C. nobilis. The findings of this study provide important clues for the regulation mechanism of total carotenoid accumulation in C. nobilis.

Overexpression of the rice ORANGE gene OsOR negatively regulates carotenoid accumulation, leads to higher tiller numbers and decreases stress tolerance in Nipponbare rice

The ORANGE (OR) gene has been reported to regulate chromoplast differentiation and enhance carotenoid biosynthesis in many dicotyledonous plants. However, the function of the OR gene in monocotyledons, especially rice, is poorly known. Here, the OR gene from rice, OsOR, was isolated and characterized by generating overexpressing and genome editing mutant lines. The OsOR-overexpressing plants exhibited pleiotropic phenotypes, such as alternating transverse green and white sectors on leaves at the early tillering stage, that were due to changes in thylakoid development and reduced carotenoid content. In addition, the number of tillers significantly increased in OsOR-overexpressing plants but decreased in osor mutant lines, a result similar to that previously reported for the carotenoid isomerase mutant mit3. The expression of the DWARF3 and DWARF53 genes that are involved in the strigolactone signalling pathway were similarly downregulated in OsOR-overexpressing plants but upregulated in osor mutants. Moreover, the OsOR-overexpressing plants exhibited greater sensitivity to salt and cold stress, and had lower total chlorophyll and higher MDA contents. All results suggest that the OsOR gene plays an important role not only in carotenoid accumulation but also in tiller number regulation and in responses to environmental stress in rice.

An RNA-seq Analysis Reveals Differential Transcriptional Responses to Different Light Qualities in Leaf Color of Camellia sinensis cv. Huangjinya

‘Huangjinya’ is a novel light-sensitive albino tea cultivar. Previously we have found that the leaves exhibit varying degrees of yellow coloration after being exposed to different light qualities, including red light (RL), blue light (BL), red + blue light (RB) and white light (WL). To understand the transcriptional response of different light qualities in leaf coloration of ‘Huangjinya’, RNA-seq analysis with three biological replicates was performed to identify differentially expressed genes (DEGs) involved in pigment metabolism pathways. With regard to porphyrin and chlorophyll metabolism, the protochlorophyllide oxidoreductase (POR) was upregulated and chlorophyllase (Chlase) was downregulated under RL compared with WL, which contributed to high chlorophyll content in ‘Huangjinya’. The upregulated POR and magnesium chelatase H subunit (CHLH) were identified under RB. BL significantly promoted carotenoid biosynthesis, accompanied by the related upregulated genes. However, upregulated xanthoxin dehydrogenase (ABA2) reduced carotenoid content under BL. Zeaxanthin epoxidase (ZEP) was upregulated and ABA2 was downregulated under RB, resulting in high accumulation of carotenoid content. BL and RL upregulated expressions of genes involved in flavonoid biosynthesis in ‘Huangjinya’. Differential expressions of genes involved in flavonoid biosynthesis was considered as the results of leaf color change. In addition, the genes related to photosynthesis were downregulated under RL, whereas these were upregulated under BL when compared with WL. In conclusion, the effect of light quality on the leaf coloration of ‘Huangjinya’ was mainly dependent on chlorophyll content by altering corresponding genes expressions. RL may promote the accumulation of chlorophyll in ‘Huangjinya’ leaves by upregulating the expression of genes related to chlorophyll synthesis (e.g., POR) and downregulating expression of genes related to chlorophyll degradation (e.g., Chlase). BL could upregulate the expression of genes related to both biosynthesis (e.g., POR, hemA) and degradation (e.g., Chlase) of chlorophyll, resulting in little change in leaf color of ‘Huangjinya’ under blue light when compared with white light. Upregulated genes involved in chlorophyll biosynthesis (e.g., POR, CHLH) induced greener color of ‘Huangjinya’ treated with RB.

The Morphological and Biochemical Effects of Feeding Hooker's Pitcher with Formica fusca or Calliphora vicina Larvae

The aim of this study was to determine if feeding Hooker’s pitcher (Nepenthes × hookeriana) with blowfly larvae (Calliphora vicina Rob-Desvoidy) or ants (Formica fusca L.) affected the plant’s biometric and biochemical parameters. The research included measurements of length and width of the laminae and pitchers, and the total contents of the ash, assimilation pigments, polyphenols, and flavonoids. These parameters were measured 30 days after the last feeding. This study demonstrated that feeding the plants with blowfly larvae resulted in increases in the lengths and widths of both the laminae and pitchers. Moreover, the laminae had reduced carotenoid content after feeding with blowfly larvae and ants whereas the pitchers of Hooker’s pitcher had increased chlorophyll and carotenoid content after feeding with blowfly larvae. Feeding Hooker’s pitcher plants with blowfly larvae also resulted in a reduction of the total polyphenol content in the laminae whereas the total flavonoid content increased in both the laminae and pitchers of Hooker’s pitcher. Feeding Nepenthes × hookeriana with insects ensures that their nutritional needs are met and leads to pitchers with good physiological condition.

Rapid metabolite response in leaf blade and petiole as a marker for shade avoidance syndrome

BackgroundShade avoidance syndrome (SAS) commonly occurs in plants experiencing vegetative shade, causing morphological and physiological changes that are detrimental to plant health and consequently crop yield. As the effects of SAS on plants are irreversible, early detection of SAS in plants is critical for sustainable agriculture. However, conventional methods to assess SAS are restricted to observing for morphological changes and checking the expression of shade-induced genes after homogenization of plant tissues, which makes it difficult to detect SAS early.ResultsUsing the model plant Arabidopsis thaliana, we introduced the use of Raman spectroscopy to measure shade-induced changes of metabolites in vivo. Raman spectroscopy detected a decrease in carotenoid contents in leaf blades and petioles of plants with SAS, which were induced by low Red:Far-red light ratio or high density conditions. Moreover, by measuring the carotenoid Raman peaks, we were able to show that the reduction in carotenoid content under shade was mediated by phytochrome signaling. Carotenoid Raman peaks showed more remarkable response to SAS in petioles than leaf blades of plants, which greatly corresponded to their morphological response under shade or high plant density. Most importantly, carotenoid content decreased shortly after shade induction but before the occurrence of visible morphological changes. We demonstrated this finding to be similar in other plant species. Comprehensive testing of Brassica vegetables showed that carotenoid content decreased during SAS, in both shade and high density conditions. Likewise, carotenoid content responded quickly to shade, in a manner similar to Arabidopsis plants.ConclusionsIn various plant species tested in this study, quantification of carotenoid Raman peaks correlate to the severity of SAS. Moreover, short-term exposure to shade can induce the carotenoid Raman peaks to decrease. These findings highlight the carotenoid Raman peaks as a biomarker for early diagnosis of SAS in plants.

Oxidative stress and antioxidant metabolites in wheat (Triticum aestivum L.) varieties during grain development under water deficit conditions

Two wheat (Triticum aestivum L.) varieties viz. WH 1105 and WH 1025 are subjected to drought stress. The non enzymatic antioxidant defense system which contains antioxidant metabolites such as ascorbic acid, glutathione and carotenoids contents were studied in drought sensitive and drought resistant varieties days after anthesis (DAA) in leaf and grain samples. As part of protective mechanism against drought, wheat plants produced more of ascorbic acid and glutathione with a concomitant decrease in carotenoid content. The increase in ascorbic acid and glutathione were more in WH 1025 than WH 1105. Carotenoids protect plants by minimizing ROS formation by quenching oxygen. The reduction in carotenoid content was observed in both wheat varieties days after anthesis (DAA) in leaf and grain samples but more reduction was observed in WH 1105 which is a drought sensitive variety of wheat. These antioxidant metabolites played a key role in protecting wheat plants against reactive oxygen species (ROS) mediated oxidative damage and their redox buffering capacity generates stress tolerance in drought tolerant wheat variety WH 1025.

Impact of high pressure and thermal processing on probiotic mixed mango and carrot juices

This study aimed to elaborate a mixed mango and carrot juice processed thermally and by high isostatic pressure (HIP) added L. plantarum. L. plantarum caused a decrease in pH and increase in acidity of the juices, but did not change the antioxidant capacity (AC), and α- and β-carotene contents. HIP maintained the microbiological quality, whereas the pasteurized juices showed high psychrotrophic counts after 35 storage days. HIP did not influence the AC, whereas the pasteurized juices showed a decrease in AC and a 30% reduction in carotenoid contents. Pasteurization reduced the polyphenoloxidase and peroxidase activities and HIP promoted a reduction in polyphenoloxidase activity but increased the peroxidase activity (~30%). Mixed juices presented good sensory acceptance (HIP juice showed the highest score). Thus, HIP showed to be more effective than thermal process, the matrix proved to be capable of maintaining the L. plantarum viability, and could be an alternative for dairy products. Practical applications The results showed that the production of the probiotics mixed juices processed by high pressure is industrially interesting, since this process was able to better preserve sensory and nutritional characteristics of the juices compared to the thermal process. In addition, this probiotic product emerges as an alternative for vegetarian’s individuals who have diets with cholesterol restriction or allergy and/or intolerance to dairy products. Furthermore, due the effectiveness of applied conservation processes and biopreservation, these products were safe for consumption during the assessed refrigerated storage period.

Linking mode of action of the model respiratory and photosynthesis uncoupler 3,5-dichlorophenol to adverse outcomes in Lemna minor

Standard chemical toxicity testing guidelines using aquatic plant Lemna minor have been developed by several international standardisation organisations. Although being highly useful for regulatory purposes by focusing on traditional adverse endpoints, these tests provide limited information about the toxic mechanisms and modes of action (MoA). The present study aimed to use selected functional assays in L. minor after exposure to 3,5-dichlorophenol (3,5-DCP) as a model to characterise the toxic mechanisms causing growth inhibition and lethality in primary producers. The results demonstrated that 3,5-DCP caused concentration-dependent effects in chloroplasts and mitochondria. Uncoupling of oxidative phosphorylation (OXPHOS), reduction in chlorophyll (Chlorophyll a and b) content, reproduction rate and frond size were the most sensitive endpoints, followed by formation of reactive oxygen species (ROS), lipid peroxidation (LPO), reduction of carotenoid content and impairment of photosynthesis efficiency. Suppression of photosystem II (PSII) efficiency, electron transport rate (ETR), chlorophyll (a and b) contents and oxidative phosphorylation (OXPHOS) were closely correlated while ROS production and LPO were negative correlated with ETR, carotenoid content and growth parameters. A network of conceptual Adverse Outcome Pathways (AOPs) was developed to decipher the causal relationships between molecular, cellular, and apical adverse effects occurring in L. minor to form a basis for future studies with similar compounds.

Eclipta yellow vein virus enhances chlorophyll destruction, singlet oxygen production and alters endogenous redox status in Andrographis paniculata

The infection of Eclipta yellow vein virus [EcYVV-IN, Accession No. KC476655], recently reported for the first time, on Andrographis paniculata was studied for redox-mediated alteration mechanism in infected plants. A. paniculata, an important medicinal plant, is used in traditional Indian, Chinese and modern system of medicine. Andrographolide, one of the foremost components of this plant, is known for its varied pharmacological properties. Our investigation provides insight into the effect of virus-induced changes in the singlet oxygen quenching due to the alteration in pigment content (chlorophyll and carotenoids) as well as activation of plant secondary metabolism along with defense activation leading to changes in enzymatic and non-enzymatic redox status. Due to infection, a reduction in carotenoid content was observed which leads to reduced quenching of singlet oxygen. An increased level of enzymatic (SOD and APX) and non-enzymatic antioxidant (DPPH, FRAP, RP, NO, TAC and TP) activities were also observed in virus-infected plants with a positive correlation (>0.9). However, CAT activity was diminished which could be either due to its proteolytic degradation or inactivation by superoxide anions (O2−.), NO or peroxynitrite radicals. A significant (p < 0.05) increase in total phenolic content was observed in the infected plants while no considerable difference was seen in the total flavonoid content. Our results highlighted the alteration in redox status caused by virus-induced biotic stress on the plants and could be useful for understanding the after effects of viral infection This study could also be helpful in developing biomimetic methods for improving the production of secondary metabolites of pharmaceutical importance.

Screening ofWithania somniferaL. Germplasm for Resistance against Leaf Spot Caused byAlternaria alternata(Fr.) Keissler

Ashwagandha (Withania somnifera L. Dunal), commonly called as ‘winter cherry. The roots, leaves and fruits of this medicinal plant possess tremendous medicinal value. In recent years the demand of Ashwagandha in the international market increases by many folds. Plant diseases are the major constraints in the production of Ashwagandha. In this study seven Ashwagandha genotypes were screened against Alternaria leaf spot under pot condition on the basis of disease severity and percent reduction in yield. Among seven genotypes RAS-10 Showed consistently resistant reaction. IC-310620(A) and IC-283942 were tolerant and moderately tolerant, while remaining genotypes were found to be susceptible to highly susceptible. During the estimation of reduction in chlorophyll and carotenoid content of the 7 genotypes, the reduction in chlorophyll content was maximum in genotype RAS-10 and minimum in IC-283942. The reduction in carotenoid content was maximum in genotype RAS-98 and minimum in RAS-7.

An R2R3-MYB transcription factor regulates carotenoid pigmentation in Mimulus lewisii flowers.

Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers and fruits. The structural genes in the highly conserved carotenoid biosynthetic pathway have been well characterized in multiple plant systems, but little is known about the transcription factors that control the expression of these structural genes. By analyzing a chemically induced mutant of Mimulus lewisii through bulk segregant analysis and transgenic experiments, we have identified an R2R3-MYB, Reduced Carotenoid Pigmentation 1 (RCP1), as the first transcription factor that positively regulates carotenoid biosynthesis during flower development. Loss-of-function mutations in RCP1 lead to down-regulation of all carotenoid biosynthetic genes and reduced carotenoid content in M.lewisii flowers, a phenotype recapitulated by RNA interference in the wild-type background. Overexpression of this gene in the rcp1 mutant background restores carotenoid production and, unexpectedly, results in simultaneous decrease of anthocyanin production in some transgenic lines by down-regulating the expression of an activator of anthocyanin biosynthesis. Identification of transcriptional regulators of carotenoid biosynthesis provides the 'toolbox' genes for understanding the molecular basis of flower color diversification in nature and for potential enhancement of carotenoid production in crop plants via genetic engineering.

Contribution made by the carotenoid cleavage dioxygenase 4 gene to yellow colour fade in azalea petals

Carotenoid content, composition, and the expression patterns of carotenoid biosynthesis and cleavage genes during petal development were compared among a yellow-flowered deciduous azalea (Rhododendron japonicum f. flavum), a white-flowered evergreen azalea (‘Miyamasatsuki’), and their progeny, to determine the factors that cause reduction in carotenoid content as the petals of the progeny develop. During the early, green petal flowering stage, total carotenoid contents were 31.27 μg g−1 Fresh Weight (F. W.) in R. japonicum f. flavum, 17.84 μg g−1 F. W. in ‘Miyamasatsuki’, and 42.18 μg g−1 F. W. in their progeny. During subsequent flower development, total carotenoid contents remained similar to the green petal stage for R. japonicum f. flavum. However, the content decreased in ‘Miyamasatsuki’ and their progeny at one day before anthesis, and became less than 3 μg g−1 F. W. during the later stages. The expression levels of PSY and PDS increased significantly in R. japonicum f. flavum than in ‘Miyamasatsuki’ as the flowers developed. Their expressions in the progeny were mid-way between both parents. The expression level of CCD4 was significantly higher in ‘Miyamasatsuki’ and the progeny than in R. japonicum f. flavum for all development stages. This result suggested that the high expression level of CCD4, which was inherited from ‘Miyamasatsuki’, was the main factor controlling the reduction in carotenoid content in the progeny.