Zeta-carotene Desaturase Research Articles

Carotenoid biosynthesis profiling unveils the variance of flower coloration in Tagetes erecta and enhances fruit pigmentation in tomato

Carotenoids play a pivotal role in plant. Tagetes erecta, commonly called marigold, has increasing nutritional and economic value due to its high level of carotenoids in flower. However, the functional genes in the carotenoid biosynthesis of T. erecta have not been studied. In this work, three T. erecta varieties with flowers of yellow, yellow-orange and orange color, respectively, were examined for carotenoids composition and corresponding expression profiling of biosynthetic genes at four developmental stages. The results indicated that the varieties with higher lutein content, orange-flower ‘Juwang’ and yellow-orange ‘Taishan’, exhibited significant upregulation of genes in the upstream biosynthesis pathway, especially PDS (phytoene desaturase), PSY (phytoene synthase) and ZDS (zeta-carotene desaturase), whereas downstream carotenoid cleavage genes CCD (carotenoid cleavage dioxygenase) were markedly downregulated throughout flower development in the highest lutein containing variety ‘Juwang’. Furthermore, marigold TePDS, TePSYS3 and TeZDS were isolated and transformed into tomato. Overexpression of TePDS or TeZDS resulted in the promotion of fruit ripening and accumulation of carotenoids in the transgenic lines. On the other hand, marigold TePSYS3 showed multiple effects, not only on fruit carotenogenesis but also on pigmentation patterns in vegetative tissues and plant growth. Taken together, the variations in expression profiles of the biosynthetic genes contribute to dynamic change in carotenoid levels and diversity of flower coloration in T. erecta. These functional genes of T. erecta were verified in tomato and provide targets for genetic improvement of fruit carotenoids accumulation.

Natural product drupacine acting on a novel herbicidal target shikimate dehydrogenase

Natural products are one of the important sources for the creation of new pesticides. Drupacine ((1R,11S,12S,13R,15S)-13-methoxy-5,7,21-trioxa-19-azahexacyclo[11.7.1.02,10.04,8.011,15.015,19]henicosa-2,4(8),9-trien-12-ol), isolated from Cephalotaxus sinensis (Chinese plum-yew), is a potent herbicidal compound containing an oxo-bridged oxygen bond structure. However, its molecular target still remains unknown. In this study, the targets of drupacine in Amaranthus retroflexus were identified by combining drug affinity responsive target stability (DARTS), cellular thermal shift assay coupled with mass spectrometry (CETSA MS), RNA-seq transcriptomic, and TMT proteomic analyses. Fifty-one and sixty-eight main binding proteins were identified by DARTS and CETSA MS, respectively, including nine co-existing binding proteins. In drupacine-treated A. retroflexus seedlings we identified 1389 up-regulated genes and 442 down-regulated genes, 34 up-regulated proteins, and 194 down-regulated proteins, respectively. Combining the symptoms and the biochemical profiles, Profilin, Shikimate dehydrogenase (SkDH), and Zeta-carotene desaturase were predicted to be the drupacine potential target proteins. At the same time, drupacine was found to bind SkDH stronger by molecular docking, and its inhibition on ArSkDH increased with the treatment concentration increase. Our results suggest that the molecular target of drupacine is SkDH, a new herbicide target, which lay a foundation for the rational design of herbicides based on new targets from natural products and enrich the target resources for developing green herbicides.

Leaves of Moringa oleifera Are Potential Source of Bioactive Compound β-Carotene: Evidence from In Silico and Quantitative Gene Expression Analysis.

Moringa oleifera is rich in bioactive compounds such as beta-carotene, which have high nutritional values and antimicrobial applications. Several studies have confirmed that bioactive-compound-based herbal medicines extracted from the leaves, seeds, fruits and shoots of M. oleifera are vital to cure many diseases and infections, and for the healing of wounds. The β-carotene is a naturally occurring bioactive compound encoded by zeta-carotene desaturase (ZDS) and phytoene synthase (PSY) genes. In the current study, computational analyses were performed to identify and characterize ZDS and PSY genes retrieved from Arabidopsis thaliana (as reference) and these were compared with the corresponding genes in M. oleifera, Brassica napus, Brassica rapa, Brassica oleracea and Bixa orellana. The BLAST results revealed that all the plant species considered in this study encode β-carotene genes with 80-100% similarity. The Pfam analysis on β-carotene genes of all the investigated plants confirmed that they belong to the same protein family and domain. Similarly, phylogenetic analysis revealed that β-carotene genes of M. oleifera belong to the same ancestral class. Using the ZDS and PSY genes of Arabidopsis thaliana as a reference, we conducted qRT-PCR analysis on RNA extracted from the leaves of M. oleifera, Brassica napus, Brassica rapa and Bixa orellana. It was noted that the most significant gene expression occurred in the leaves of the studied medicinal plants. We concluded that not only are the leaves of M. oleifera an effective source of bioactive compounds including beta carotene, but also the leaves of Brassica napus, Brassica rapa and Bixa orellana can be employed as antibiotics and antioxidants against bacterial or microbial infections.

Chromoplast plastoglobules recruit the carotenoid biosynthetic pathway and contribute to carotenoid accumulation during tomato fruit maturation.

Tomato (Solanum lycopersicum) fruit maturation is associated with a developmental transition from chloroplasts (in mature green fruit) to chromoplasts (in red fruit). The hallmark red color of ripe tomatoes is due to carotenogenesis and accumulation of the red carotenoid lycopene inside chromoplasts. Plastoglobules (PG) are lipid droplets in plastids that are involved in diverse lipid metabolic pathways. In tomato, information on the possible role of PG in carotogenesis and the PG proteome is largely lacking. Here, we outline the role of PG in carotenogenesis giving particular attention to tomato fruit PG proteomes and metabolomes. The proteome analysis revealed the presence of PG-typical FBNs, ABC1K-like kinases, and metabolic enzymes, and those were decreased in the PG of tomato chromoplasts compared to chloroplasts. Notably, the complete β-carotene biosynthesis pathway was recruited to chromoplast PG, and the enzymes PHYTOENE SYNTHASE 1 (PSY-1), PHYTOENE DESATURASE (PDS), ZETA-CAROTENE DESATURASE (ZDS), and CAROTENOID ISOMERASE (CRTISO) were enriched up to twelvefold compared to chloroplast PG. We profiled the carotenoid and prenyl lipid changes in PG during the chloroplast to chromoplast transition and demonstrated large increases of lycopene and β-carotene in chromoplast PG. The PG proteome and metabolome are subject to extensive remodeling resulting in high accumulation of lycopene during the chloroplast-to-chromoplast transition. Overall, the results indicate that PGs contribute to carotenoid accumulation during tomato fruit maturation and suggest that they do so by functioning as a biosynthetic platform for carotenogenesis.

Transcriptome and Metabolome Analysis of Color Changes during Fruit Development of Pepper (Capsicum baccatum).

Fruit color is one of the most critical characteristics of pepper. In this study, pepper (Capsicum baccatum L.) fruits with four trans-coloring periods were used as experimental materials to explore the color conversion mechanism of pepper fruit. By transcriptome and metabolome analysis, we identified a total of 307 flavonoid metabolites, 68 carotenoid metabolites, 29 DEGs associated with flavonoid biosynthesis, and 30 DEGs related to carotenoid biosynthesis. Through WGCNA (weighted gene co-expression network analysis) analysis, positively correlated modules with flavonoids and carotenoids were identified, and hub genes associated with flavonoid and carotenoid synthesis and transport were anticipated. We identified Pinobanksin, Naringenin Chalcone, and Naringenin as key metabolites in the flavonoid biosynthetic pathway catalyzed by the key genes chalcone synthase (CHS CQW23_29123, CQW23_29380, CQW23_12748), cinnamic acid 4-hydroxylase (C4H CQW23_16085, CQW23_16084), cytochrome P450 (CYP450 CQW23_19845, CQW23_24900). In addition, phytoene synthase (PSY CQW23_09483), phytoene dehydrogenase (PDS CQW23_11317), zeta-carotene desaturase (ZDS CQW23_19986), lycopene beta cyclase (LYC CQW23_09027), zeaxanthin epoxidase (ZEP CQW23_05387), 9-cis-epoxycarotenoid dioxygenase (NCED CQW23_17736), capsanthin/capsorubin synthase (CCS CQW23_30321) are key genes in the carotenoid biosynthetic pathway, catalyzing the synthesis of key metabolites such as Phytoene, Lycopene, β-carotene and ε-carotene. We also found that transcription factor families such as p450 and NBARC could play important roles in the biosynthesis of flavonoids and carotenoids in pepper fruits. These results provide new insights into the interaction mechanisms of genes and metabolites involved in the biosynthesis of flavonoids and carotenoids in pepper fruit leading to color changes in pepper fruit.

SunUp and Sunset genomes revealed impact of particle bombardment mediated transformation and domestication history in papaya.

Transgenic papaya is widely publicized for controlling papaya ringspot virus. However, the impact of particle bombardment on the genome remains unknown. The transgenic SunUp and its progenitor Sunset genomes were assembled into 351.5 and 350.3 Mb in nine chromosomes, respectively. We identified a 1.64 Mb insertion containing three transgenic insertions in SunUp chromosome 5, consisting of 52 nuclear-plastid, 21 nuclear-mitochondrial and 1 nuclear genomic fragments. A 591.9 kb fragment in chromosome 5 was translocated into the 1.64 Mb insertion. We assembled a gapless 9.8 Mb hermaphrodite-specific region of the Yh chromosome and its 6.0 Mb X counterpart. Resequencing 86 genomes revealed three distinct groups, validating their geographic origin and breeding history. We identified 147 selective sweeps and defined the essential role of zeta-carotene desaturase in carotenoid accumulation during domestication. Our findings elucidated the impact of particle bombardment and improved our understanding of sex chromosomes and domestication to expedite papaya improvement.

Transcriptome analysis of a new maize albino mutant reveals that zeta-carotene desaturase is involved in chloroplast development and retrograde signaling

Carotenoids are a group of natural tetraterpenoid pigments with essential roles in a variety of physiological processes of plants. Although carotenoid biosynthesis has been well characterized, the genetic basis of the pathway, especially in crop plants, is largely unknown. In this study, we characterized a new albino maize mutant called albino1 (alb1), which was obtained from a Mutator mutagenized population. The alb1 mutant showed defective chloroplast development and declined photosynthetic pigments, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that ALB1 encoded a putative ζ-carotene desaturase (ZDS) involved in carotenoid biosynthesis. Measurement of carotenoids revealed that several major carotenoid compounds downstream of the ZDS were significantly reduced in alb1 mutant, indicating that ALB1 is a functional ZDS. Further transcriptome analysis revealed that several groups of nuclear genes involved in photosynthesis, such as light-harvesting complex, pigment metabolism, and chloroplast function, were significantly down-regulated in alb1 compared with wide type. Interestingly, expression of some maize plastid-localized nuclear genes, including POR, CAO, Lhcb, and RbcS, was substantially reduced in alb1 plants. Furthermore, treatment of the inhibitor fluridone significantly rescued gene transcripts of these nucleus-encoded genes in alb1 mutant, which supported the retrograde signaling of ζ-carotene/phytofluene derived molecules. These results suggested that ALB1/ZDS might function as a regulator to coordinate nuclear photosynthetic gene expression in plastid-to-nucleus retrograde signaling during development of maize plants. Together, these results have demonstrated that ALB1/ZDS is essential for carotenoids biosynthesis and plays crucial roles in chloroplast biogenesis and development in maize.

Transcription activation of β-carotene biosynthetic genes at the initial stage of stresses as an indicator of the increased β-carotene accumulation in isolated Dunaliella salina strain GY-H13

β-carotene is an efficient antioxidant and its accumulation is an oxidative response to stressors. Dunaliella salina strain GY-H13 is rich in β-carotene under environmental stresses, which was selected as material to understand the molecular mechanism underlying β-carotene biosynthesis. Seven full length cDNA sequences in β-carotene biosynthesis pathway were cloned, including geranylgeranyl pyrophosphate synthase (GGPS), phytoene synthase (PSY), phytoene desaturase (PDS), 15-cis-zeta-carotene isomerase (ZISO), zeta-carotene desaturase (ZDS), prolycopene isomerase (CRTISO), lycopene beta-cyclase (LCYb). The seven protein sequences from the strain GY-H13 showed the highest similarity with other D. salina strains. Especially, PSY, PDS and LCYb protein sequences shared 100 % identity. Phylogenetic analysis indicated all proteins from GY-H13 firstly clustered with those from other D. salina strains with a bootstrap of 100 %. Multiple alignment indicated several distinct conserved motifs such as aspartate-rich domain (ARD), dinucleotide binding domain (DBD), and carotene binding domain (CBD). These motifs are located near ligand-binding pocket, which may be required for the activity of enzyme. Expression levels of these genes and β-carotene content were measured over 24-h cycle, showing clear daily dynamics. All genes were dramatically up-regulated in the morning but the highest accumulation of β-carotene was observed at noon, suggesting a lag-effect between gene transcription and biological response. Furthermore, the accumulation of β-carotene increased under nitrogen deficiency, Cd exposure and high light and decreased under high salinity in a time-dependent manner. No gene of β-carotene biosynthesis was up-regulated by high salinity while most genes were activated by the other stresses at the beginning stage of exposure. Growth inhibition and oxidative damage were also observed under high salinity. Overall, transcription activation of β-carotene biosynthetic genes at the initial stage of stress exposure is a determinant of the increased accumulation of β-carotene in microalgae, which help their survive under harsh environments. The newly isolated D. salina strain GY-H13 would be a promising microalgae model for investigating the molecular mechanism of stress-induced β-carotene biosynthesis.

The Solanum melongena COP1 delays fruit ripening and influences ethylene signaling in tomato

The regulatory protein CONSTITUTIVE PHOTOMORPHOGENIC (COP) 1 is a key repressor of photomorphogenesis; it regulates numerous developmental processes and responds to biotic and abiotic stress in plants. Here, we report the role of a novel and uncharacterized Solanum melongena COP1 (SmCOP1) gene in tomato (Solanum lycopersicum) during fruit ripening. It was observed that SmCOP1 expressed in mature leaves and fruits, while the transcripts of SmCOP1 increased significantly with the onset of fruit ripening in tomato. To further understand the SmCOP1 function, an overexpression (OE) vector carrying SmCOP1 gene was constructed and transformed into tomato plants. The OE of SmCOP1 delays fruit ripening by about three to six days compared to the wild-type (WT) fruits. SmCOP1-OE fruits decreased while seedlings increased their ethylene production in comparison with the WT. Moreover, the ethylene biosynthesis genes (ACO1, ACO3, and ACS2) and ethylene inducible genes (E4 and E8), which participate in tomato fruit ripening, were suppressed. The carotenoid accumulation and expression level of carotenoid biosynthesis genes such as phytoene synthase 1 (PSY1), phytoene desaturase, (PDS), and zeta-carotene desaturase (ZDS) were also reduced in OE fruits. Additionally, total chlorophyll contents were reduced, and expression of chlorophyll biosynthesis genes were significantly down-regulated in SmCOP1-OE lines. The SmCOP1-OE seedlings showed shorter hypocotyl lengths and were more sensitive to 1-aminocyclopropane-1-carboxylate (ACC) than were WT seedlings. In summary, SmCOP1-OE plays a pivotal role in the inhibition of tomato fruit ripening, reducing carotenoid contents and lowering ethylene production in fruits.

Key proteins associated to coloured compounds of peach peel using iTRAQ proteomic techniques during development and postharvest

Abstract This study aimed to investigate the key coloured compounds (anthocyanins, carotenoids…etc) and the key proteins associated to their synthesis or degradation of peach fruit peel (Prunus persica ‘Hujingmilu’) using iTRAQ techniques at different peach developmental stages and during the postharvest period. Peach fruits were collected 50 d, 90 d, 95 d, 100 d, and 105 day after flowering, as well as fruits being stored for 3 days after picking at 105 days after flowering. The key coloured compounds of ‘Hujingmilu ‘honey peach peel is composed of, among others, chlorophyll, anthocyanin, carotenoids, zeaxanthin, and lycopene. Peel color was regulated by chlorophyll degradation pathways, carotenoid metabolism pathways, and anthocyanin metabolism pathways, the iTRAQ technique identified 1848 unique proteins, of which 842 were related to biological processes, and 25 were related to color and 33 were related to energy transfer during fruit development and postharvest. During the development of peach fruit, light-harvesting complex chlorophyll a/b binding protein (CAB) and protochlorophyllide reductase(POR) are the key functional proteins for regulating chlorophyll metabolism, anthocyanidin 3-O-glucosyltransferase (3 G T) and UFGT are the key functional proteins for regulating anthocyanidin metabolism, PSY, zeta-carotene desaturase (ZCD) and carotenoid cleavage dioxygenase (CCD) are the key functional proteins for regulating carotenoid metabolism during the development and the postharvest period of peach fruit. Mg-protoporphyrin IX chelatase and pheophorbide a oxygenase (PAO) are the key functional proteins for regulating chlorophyll metabolism during postharvest. The key proteins were regulated a little earlier or accompany with the increase or decrease of peach peel coloured compounds. These results provide further understanding of the key coloured compounds of peach peel color, key proteins associated to coloured compounds, and reveal how the differential proteins take part in coloured compound metabolism pathway during fruit development and postharvest.

Medically important carotenoids from Momordica charantia and their gene expressions in different organs

Carotenoids, found in the fruit and different organs of bitter melon (Momordica charantia), have attracted great attention for their potential health benefits in treating several major chronic diseases. Therefore, study related to the identification and quantification of the medically important carotenoid metabolites is highly important for the treatment of various disorderes. The present study involved in the identification and quantification of the various carotenoids present in the different organs of M. charantia and the identification of the genes responsible for the accumulation of the carotenoids with respect to the transcriptome levels were investigated. In this study, using the transcriptome database of bitter melon, a partial-length cDNA clone encoding geranylgeranyl pyrophosphate synthase (McGGPPS2), and several full-length cDNA clones encoding geranylgeranyl pyrophosphate synthase (McGGPPS1), zeta-carotene desaturase (McZDS), lycopene beta-cyclase (McLCYB), lycopene epsilon cyclases (McLCYE1 and McLCYE2), beta-carotene hydroxylase (McCHXB), and zeaxanthin epoxidase (McZEP) were identified in bitter melon. The expression levels of the mRNAs encoding these eight putative biosynthetic enzymes, as well as the accumulation of lycopene, α-carotene, lutein, 13Z-β-carotene, E-β-carotene, 9Z-β-carotene, β-cryptoxanthin, zeaxanthin, antheraxanthin, and violaxanthin were investigated in different organs from M. charantia as well as in the four different stages of its fruit maturation. Transcripts were found to be constitutively expressed at high levels in the leaves where carotenoids were also found at the highest levels. Collectively, these results indicate that the putative McGGPPS2, McZDS, McLCYB, McLCYE1, McLCYE2, and McCHXB enzymes might be key factors in controlling carotenoid content in bitter melon. In conclusion, the over expression of the carotenoid biosynthetic genes from M. charantia crops to increase the yield of these medically important carotenoids.

Carotenoid accumulation in durian (Durio zibethinus) fruit is affected by ethylene via modulation of carotenoid pathway gene expression

Carotenoid content in durian (Durio zibethinus) fruit is an important aspect of fruit quality, with different cultivars distinguished by differing pigmentation. We have studied the dependence of carotenogenesis on ethylene. Fruit of the cultivar ‘Chanee’ harvested at the mature stage were either left untreated (controls), treated with 1-methylcyclopropene (1-MCP) for 12 h, or treated with application of an aqueous ethephon solution to the stem end, or treated for 12 h with 1-MCP followed by ethephon application. Fruit were then stored for 9 d at 25 °C. Pulp color of durian became steadily yellowish as a result of accumulation of carotenoids, which were mainly beta-carotene, and alpha-carotene, with a minor amount of zeaxanthin and lutein. 1-MCP delayed the increase in the accumulation of beta-carotene, alpha-carotene, and zeaxanthin, but not lutein. In contrast, ethephon had no significant effect on carotenoid accumulation. The expression of zeta-carotene desaturase (ZDS), lycopene beta-cyclase (LCYB), chromoplast specific lycopene beta-cyclase (CYCB) and beta-carotene hydroxylase (BCH) genes was highly correlated with carotenoid content and pulp color.1-MCP resulted in significant down-regulation of ZDS, LCYB, CYCB and BCH expression. The accumulation of beta-carotene and alpha-carotene appears to be controlled by the level of expression of LCYB gene, whose function was tested in bacteria to show conversion of lycopene and delta-carotene to beta-carotene and alpha-carotene, respectively. These results suggest that ripening-induced carotenoid accumulation is regulated by endogenous ethylene controlling the expression of key genes such as LCYB.

Mutations in the maize zeta-carotene desaturase gene lead to viviparous kernel.

Preharvest sprouting reduces the maize quality and causes a significant yield loss in maize production. vp-wl2 is a Mutator (Mu)-induced viviparous mutant in maize, causing white or pale yellow kernels, dramatically reduced carotenoid and ABA content, and a high level of zeta-carotene accumulation. Here, we reported the cloning of the vp-wl2 gene using a modified digestion-ligation-amplification method (DLA). The results showed that an insertion of Mu9 in the first intron of the zeta-carotene desaturase (ZDS) gene results in the vp-wl2 mutation. Previous studies have suggested that ZDS is likely the structural gene of the viviparous9 (vp9) locus. Therefore, we performed an allelic test using vp-wl2 and three vp9 mutants. The results showed that vp-wl2 is a novel allele of the vp9 locus. In addition, the sequences of ZDS gene were identified in these three vp9 alleles. The vp-wl2 mutant gene was subsequently introgressed into four maize inbred lines, and a viviparous phenotype was observed with yield losses from 7.69% to 13.33%.

Transcriptome sequencing and metabolic pathways of astaxanthin accumulated in Haematococcus pluvialis mutant under 15% CO2

Transcriptome sequencing and annotation was performed on Haematococcus pluvialis mutant red cells induced with high light under 15% CO2 to demonstrate why astaxanthin yield of the mutant was 1.7 times higher than that of a wild strain. It was found that 56% of 1947 differentially expressed genes were upregulated in mutant cells. Most significant differences were found in unigenes related to photosynthesis, carotenoid biosynthesis and fatty acid biosynthesis pathways. The pyruvate kinase increased by 3.5-fold in mutant cells. Thus, more pyruvate, which was beneficial to carotenoids and fatty acid biosynthesis, was generated. Phytoene synthase, zeta-carotene desaturase, lycopene beta-cyclase involved in β-carotene biosynthesis in mutant cells were upregulated by 10.4-, 4.4-, and 5.8-fold, respectively. Beta-carotene 3-hydroxylase catalyzing conversion of β-carotene into astaxanthin was upregulated by 18.4-fold. The fatty acid biosynthesis was promoted because of the upregulation of acetyl-CoA synthetase and acetyl-CoA carboxylase, thus increasing astaxanthin esterification and accumulation in mutant cells.

Zinc Oxide Nanoparticles Affect Biomass Accumulation and Photosynthesis in Arabidopsis.

Dramatic increase in the use of nanoparticles (NPs) in a variety of applications greatly increased the likelihood of the release of NPs into the environment. Zinc oxide nanoparticles (ZnO NPs) are among the most commonly used NPs, and it has been shown that ZnO NPs were harmful to several different plants. We report here the effects of ZnO NPs exposure on biomass accumulation and photosynthesis in Arabidopsis. We found that 200 and 300 mg/L ZnO NPs treatments reduced Arabidopsis growth by ∼20 and 80%, respectively, in comparison to the control. Pigments measurement showed that Chlorophyll a and b contents were reduced more than 50%, whereas carotenoid contents remain largely unaffected in 300 mg/L ZnO NPs treated Arabidopsis plants. Consistent with this, net rate of photosynthesis, leaf stomatal conductance, intercellular CO2 concentration and transpiration rate were all reduced more than 50% in 300 mg/L ZnO NPs treated plants. Quantitative RT-PCR results showed that expression levels of chlorophyll synthesis genes including CHLOROPHYLL A OXYGENASE (CAO), CHLOROPHYLL SYNTHASE (CHLG), COPPER RESPONSE DEFECT 1 (CRD1), MAGNESIUM-PROTOPORPHYRIN IX METHYLTRANSFERASE (CHLM) and MG-CHELATASE SUBUNIT D (CHLD), and photosystem structure gene PHOTOSYSTEM I SUBUNIT D-2 (PSAD2), PHOTOSYSTEM I SUBUNIT E-2 (PSAE2), PHOTOSYSTEM I SUBUNIT K (PSAK) and PHOTOSYSTEM I SUBUNIT K (PSAN) were reduced about five folds in 300 mg/L ZnO NPs treated plants. On the other hand, elevated expression, though to different degrees, of several carotenoids synthesis genes including GERANYLGERANYL PYROPHOSPHATE SYNTHASE 6 (GGPS6), PHYTOENE SYNTHASE (PSY) PHYTOENE DESATURASE (PDS), and ZETA-CAROTENE DESATURASE (ZDS) were observed in ZnO NPs treated plants. Taken together, these results suggest that toxicity effects of ZnO NPs observed in Arabidopsis was likely due to the inhibition of the expression of chlorophyll synthesis genes and photosystem structure genes, which results in the inhibition of chlorophylls biosynthesis, leading to the reduce in photosynthesis efficiency in the plants.

Identification of differentially expressed genes associated with flower color in peach using genome-wide transcriptional analysis.

Flower color is an important trait of the ornamental peach (Prunus persica L.). However, the mechanism responsible for the different colors that appear in the same genotype remains unclear. In this study, red samples showed higher anthocyanins content (0.122 ± 0.009 mg/g), which was significantly different from that in white samples (0.066 ± 0.010 mg/g). Similarly to carotenoids content, red extract (0.058 ± 0.004 mg/L) was significantly higher in white extract (0.015 ± 0.004 mg/L). We estimated gene expression using Illumina sequencing technology in libraries from white and red flower buds. A total of 3,599,960 and 3,464,141 tags were sequenced from the 2 libraries, respectively. Moreover, we identified 106 significantly differentially expressed genes between the 2 libraries. Among these, 78 and 28 represented transcripts with a higher or lower abundance of more than 2-fold than in the white flower library, respectively. GO annotation indicated that highly ranked genes were involved in the pigment biosynthetic process. Expression patterns of 11 genes were verified using quantitative reverse transcription-polymerase chain reaction assays. The results suggest that hydroxycinnamoyl-coenzyme A shikimate/quinate hydroxycinnamoyltransferase, 2-oxoglutarate-dependent dioxygenase, isoflavone reductase, riboflavin kinase, zeta-carotene desaturase, and ATP binding cassette transporter may be associated with the flower color formation. Our results may be useful for scientists focusing on Prunus persica floral development and biotechnology.

Expression Analysis of Salt Stress on Carotenoid Pathway Genes in Watermelon

Carotenoids, the naturally occurring isoprenoids form essential components of photosynthetic antenna and reaction centre complexes. Thus they play a significant role in absorption, dissipation and transfer of light energy for the process of photosynthesis. The expression of salt stress on carotenoid gene in watermelon leaves were studied. For that watermelon plants were subjected to different concentration of salt water. Morphological characters such as plant height, no. of fruits per plant,chlorophyll content and expression of four major carotenoid pathway genes such as phytoene synthase(PSY), phytoene desaturase(PDS), zeta carotene desaturase(ZDS) and lycopene beta cyclase(LCY-β) were analysed. The quantitative expression analysis using real time PCR has shown a decrease in the expression of all the studied genes as the salt concentration increased. Among the different concentrations of NaCl used for the experiment, it was seen that 200 mM was most detrimental for the carotenoid gene expression.Lycopene beta cyclase, the enzyme that converts lycopene to beta carotene was seen to be highly affected compared to other genes studied showing a 1.87 fold inhibition in its expression at 200 mM NaCl.

Cloning and functional expression of zeta-carotene desaturase, a novel carotenoid biosynthesis gene from Ficus carica

Carotene desaturation, an essential step in the carotenoid biosynthesis pathway, is catalyzed by two enzymes, phytoene desaturase (PDS) and ζ-carotene desaturase (zeta carotene desaturase, ZDS). Here we describe cloning and ＂E. Coli expression＂ of zds-Fc, a novel Ficus carica ζ-carotene desaturase catalyzing dehydrogenation of ζ-carotene into neurosporene and finally lycopene. The ζ-carotene desaturase (ZDS) gene was amplified from the fig tree by rapid amplification of cDNA ends (RACE) and spanned a 1746 bp open reading frame (ORF), encoding a protein of 582 amino acid residues with a predicted molecular weight of 64kD. The N-terminal region of this polypeptide contained a putative transit sequence for plastid targeting. By phylogenetic and sequence analyses, zds-Fc showed high homology with previously described ζ-carotene desaturases from higher plant species (Al-Babili et al. 1998; Cong et al. 2009; Matthews et al. 2003; Yan et al. 2011). Additionally, sequence analysis revealed a high degree of conservation among plant ZDSs. The deduced ZDS protein, designated FcZDS, also contains an N-terminus dinucleotide-binding, followed by a conserved region identified in other carotene desaturase sequences. These data, taken together, confirm our cloned zds-Fc as an integral part of the ZDS family of proteins.

Allelic Variation at the TaZds-A1 Locus on Wheat Chromosome 2A and Development of a Functional Marker in Common Wheat

ζ(zeta)-carotene desaturase (ZDS) is a key enzyme for carotenoid biosynthesis, demonstrating high association with the yellow pigment (YP) content in wheat grain. Cloning ZDS gene and developing functional markers are important for marker-assisted selection in wheat breeding. In the present study, the full-length DNA sequence of a ZDS gene on wheat chromosome 2A, designated TaZds-A1, was cloned, with 14 exons and 13 introns, and it has an open reading frame (ORF) of 1 707 bp, encoding 568 amino acid residues. A co-dominant functional marker, YP2A-1, was designed based on the polymorphisms of two alleles at the locus, TaZds-A1a and TaZds-A1b, yielding 183- and 179-bp fragments in TaZds-A1a and TaZds-A1b genotypes, respectively. A new QTL for YP content was detected on chromosome 2A, co-segregating with the functional marker YP2A-1 and TaZds-A1; it explained 11.3% of the phenotypic variance for YP content in a doubled haploid (DH) population from Zhongyou 9507/CA9632. Among 217 Chinese wheat cultivars and advanced lines, the average grain YP content of 126 cultivars with TaZds-A1b allele was 7.8% higher than that of 91 cultivars with TaZds-A1a allele.

De novo transcriptome sequencing of Momordica cochinchinensis to identify genes involved in the carotenoid biosynthesis

The ripe fruit of Momordica cochinchinensis Spreng, known as gac, is featured by very high carotenoid content. Although this plant might be a good resource for carotenoid metabolic engineering, so far, the genes involved in the carotenoid metabolic pathways in gac were unidentified due to lack of genomic information in the public database. In order to expedite the process of gene discovery, we have undertaken Illumina deep sequencing of mRNA prepared from aril of gac fruit. From 51,446,670 high-quality reads, we obtained 81,404 assembled unigenes with average length of 388 base pairs. At the protein level, gac aril transcripts showed about 81.5% similarity with cucumber proteomes. In addition 17,104 unigenes have been assigned to specific metabolic pathways in Kyoto Encyclopedia of Genes and Genomes, and all of known enzymes involved in terpenoid backbones biosynthetic and carotenoid biosynthetic pathways were also identified in our library. To analyze the relationship between putative carotenoid biosynthesis genes and alteration of carotenoid content during fruit ripening, digital gene expression analysis was performed on three different ripening stages of aril. This study has revealed putative phytoene synthase, 15-cis-phytone desaturase, zeta-carotene desaturase, carotenoid isomerase and lycopene epsilon cyclase might be key factors for controlling carotenoid contents during aril ripening. Taken together, this study has also made availability of a large gene database. This unique information for gac gene discovery would be helpful to facilitate functional studies for improving carotenoid quantities.