Structures and functions of carotenoids bound to reaction centers from purple photosynthetic bacteria

The photoprotective function of 15,15'-cis-carotenoids bound to the photosynthetic reaction centers (RCs) of purple bacteria has been studied using carotenoids reconstituted into carotenoidless RCs from Rhodobacter sphaeroides strain R26.1. The triplet-energy level of the carotenoid has been proposed to affect the quenching of the triplet state of special-pair bacteriochlorophyll (P). This was investigated using microsecond flash photolysis to detect the carotenoid triplets as a function of the number of conjugated double bonds, n. The carotenoid triplet signals were extracted by using singular-value decomposition (SVD) of the huge matrices data, and were confirmed for those having n = 8 to 11. This interpretation assumes that the reconstituted carotenoids occupy the same binding site in the RC. We have been able to confirm this assumption using X-ray crystallography to determine the structures of carotenoidless, wild-type carotenoid-containing, and 3,4-dihydro-spheroidene-reconstituted RCs. The X-ray study also emphasized the importance of the methoxy group of the carotenoids for binding to the RCs. Electroabsorption (Stark) spectroscopy was used to investigate the effect of the carotenoid on the electrostatic field around P. This electrostatic field changed by 10 % in the presence of the carotenoid

A C35 Carotenoid Biosynthetic Pathway

Upon coexpression with Erwinia geranylgeranyldiphosphate (GGDP) synthase in Escherichia coli, C30 carotenoid synthase CrtM from Staphylococcus aureus produces novel carotenoids with the asymmetrical C35 backbone. The products of condensation of farnesyldiphosphate and GDP, C35 structures comprise 40 to 60% of total carotenoid accumulated. Carotene desaturases and carotene cyclases from C40 or C30 pathways accepted and converted the C35 substrate, thus creating a C35 carotenoid biosynthetic pathway in E. coli. Directed evolution to modulate desaturase step number, together with combinatorial expression of the desaturase variants with lycopene cyclases, allowed us to produce at least 10 compounds not previously described. This result highlights the plastic and expansible nature of carotenoid pathways and illustrates how combinatorial biosynthesis coupled with directed evolution can rapidly access diverse chemical structures

Assessment of carotenoid production by Dunaliella salina in different culture systems and operation regimes

The effect of operation regime and culture system on carotenoid productivity by the halotolerant alga Dunaliella salina has been analyzed. Operation strategies tested included batch and semi continuous regime, as well as a two-stage approach run simultaneously in both, open tanks and closed reactor. The best results were obtained with the closed tubular photobioreactor. The highest carotenoid production (328.8 mg carotenoid l−1 culture per month) was achieved with this culture system operated following the two-stage strategy. Also, closed tubular photobioreactor provided the highest carotenoid contents (10% of dry weight) in Dunaliella biomass and β-carotene abundance (90% of total carotenoids) as well as the highest 9-cis to all-trans β-carotene isomer ratio (1.5 at sunrise).Comisión Interministerial de Ciencia y Tecnología IFD 1997-1780IFAPA CO3-125Plan Andaluz de Investigación CVI13

Genome-Wide Association Study and Pathway-Level Analysis of Kernel Color in Maize.

Rapid development and adoption of biofortified, provitamin A-dense orange maize (Zea mays L.) varieties could be facilitated by a greater understanding of the natural variation underlying kernel color, including as it relates to carotenoid biosynthesis and retention in maize grain. Greater abundance of carotenoids in maize kernels is generally accompanied by deeper orange color, useful for distinguishing provitamin A-dense varieties to consumers. While kernel color can be scored and selected with high-throughput, low-cost phenotypic methods within breeding selection programs, it remains to be well established as to what would be the logical genetic loci to target for selection for kernel color. We conducted a genome-wide association study of maize kernel color, as determined by colorimetry, in 1,651 yellow and orange inbreds from the Ames maize inbred panel. Associations were found with y1, encoding the first committed step in carotenoid biosynthesis, and with dxs2, which encodes the enzyme responsible for the first committed step in the biosynthesis of the isoprenoid precursors of carotenoids. These genes logically could contribute to overall carotenoid abundance and thus kernel color. The lcyE and zep1 genes, which can affect carotenoid composition, were also found to be associated with colorimeter values. A pathway-level analysis, focused on genes with a priori evidence of involvement in carotenoid biosynthesis and retention, revealed associations for dxs3 and dmes1, involved in isoprenoid biosynthesis; ps1 and vp5, within the core carotenoid pathway; and vp14, involved in cleavage of carotenoids. Collectively, these identified genes appear relevant to the accumulation of kernel color

A foundation for provitamin A biofortification of maize: genome-wide association and genomic prediction models of carotenoid levels.

Efforts are underway for development of crops with improved levels of provitamin A carotenoids to help combat dietary vitamin A deficiency. As a global staple crop with considerable variation in kernel carotenoid composition, maize (Zea mays L.) could have a widespread impact. We performed a genome-wide association study (GWAS) of quantified seed carotenoids across a panel of maize inbreds ranging from light yellow to dark orange in grain color to identify some of the key genes controlling maize grain carotenoid composition. Significant associations at the genome-wide level were detected within the coding regions of zep1 and lut1, carotenoid biosynthetic genes not previously shown to impact grain carotenoid composition in association studies, as well as within previously associated lcyE and crtRB1 genes. We leveraged existing biochemical and genomic information to identify 58 a priori candidate genes relevant to the biosynthesis and retention of carotenoids in maize to test in a pathway-level analysis. This revealed dxs2 and lut5, genes not previously associated with kernel carotenoids. In genomic prediction models, use of markers that targeted a small set of quantitative trait loci associated with carotenoid levels in prior linkage studies were as effective as genome-wide markers for predicting carotenoid traits. Based on GWAS, pathway-level analysis, and genomic prediction studies, we outline a flexible strategy involving use of a small number of genes that can be selected for rapid conversion of elite white grain germplasm, with minimal amounts of carotenoids, to orange grain versions containing high levels of provitamin A

Carotenoid biosynthesis and overproduction in Corynebacterium glutamicum

Heider S, Peters-Wendisch P, Wendisch VF. Carotenoid biosynthesis and overproduction in Corynebacterium glutamicum. BMC Microbiology. 2012;12(1): 198.Background Corynebacterium glutamicum contains the glycosylated C50 carotenoid decaprenoxanthin as yellow pigment. Starting from isopentenyl pyrophosphate, which is generated in the non-mevalonate pathway, decaprenoxanthin is synthesized via the intermediates farnesyl pyrophosphate, geranylgeranyl pyrophosphate, lycopene and flavuxanthin. Results Here, we showed that the genes of the carotenoid gene cluster crtE-cg0722-crtBIYeYfEb are co-transcribed and characterized defined gene deletion mutants. Gene deletion analysis revealed that crtI, crtEb, and crtYeYf, respectively, code for the only phytoene desaturase, lycopene elongase, and carotenoid C45/C50 epsilon-cyclase, respectively. However, the genome of C. glutamicum also encodes a second carotenoid gene cluster comprising crtB2I2-1/2 shown to be co-transcribed, as well. Ectopic expression of crtB2 could compensate for the lack of phytoene synthase CrtB in C. glutamicum DeltacrtB, thus, C. glutamicum possesses two functional phytoene synthases, namely CrtB and CrtB2. Genetic evidence for a crtI2-1/2 encoded phytoene desaturase could not be obtained since plasmid-borne expression of crtI2-1/2 did not compensate for the lack of phytoene desaturase CrtI in C. glutamicum DeltacrtI. The potential of C. glutamicum to overproduce carotenoids was estimated with lycopene as example. Deletion of the gene crtEb prevented conversion of lycopene to decaprenoxanthin and entailed accumulation of lycopene to 0.03 +/- 0.01 mg/g cell dry weight (CDW). When the genes crtE, crtB and crtI for conversion of geranylgeranyl pyrophosphate to lycopene were overexpressed in C. glutamicum DeltacrtEb intensely red-pigmented cells and an 80 fold increased lycopene content of 2.4 +/- 0.3 mg/g CDW were obtained. Conclusion C. glutamicum possesses a certain degree of redundancy in the biosynthesis of the C50 carotenoid decaprenoxanthin as it possesses two functional phytoene synthase genes. Already metabolic engineering of only the terminal reactions leading to lycopene resulted in considerable lycopene production indicating that C. glutamicum may serve as a potential host for carotenoid production

Fruit over sunbed : carotenoid skin coloration is found more attractive than melanin coloration

Skin coloration appears to play a pivotal part in facial attractiveness. Skin yellowness contributes to an attractive appearance and is influenced both by dietary carotenoids and by melanin. While both increased carotenoid coloration and increased melanin coloration enhance apparent health in Caucasian faces by increasing skin yellowness, it remains unclear firstly, whether both pigments contribute to attractiveness judgements, secondly, whether one pigment is clearly preferred over the other, and thirdly, whether these effects depend on the sex of the face. Here, in three studies, we examine these questions using controlled facial stimuli transformed to be either high or low in (a) carotenoid coloration, or (b) melanin coloration. We show, firstly, that both increased carotenoid coloration and increased melanin coloration are found attractive compared to lower levels of these pigments. Secondly, we show that carotenoid coloration is consistently preferred over melanin coloration when levels of coloration are matched. In addition, we find an effect of the sex of stimuli with stronger preferences for carotenoids over melanin in female compared to male faces, irrespective of the sex of the observer. These results are interpreted as reflecting preferences for sex-typical skin coloration: men have darker skin than women and high melanisation in male faces may further enhance this masculine trait, thus carotenoid coloration is not less desirable, but melanin coloration is relatively more desirable in males compared to females. Taken together, our findings provide further support for a carotenoid-linked health-signalling system that is highly important in mate choice.PostprintPeer reviewe

Carotenoid triplet state formation in Rhodobacter sphaeroides R-26 reaction centers exchanged with modified bacteriochlorophyll pigments and reconstituted with spheroidene

Triplet state electron paramagnetic resonance (EPR) experiments have been carried out at X-band on Rb. sphaeroides R-26 reaction centers that have been reconstituted with the carotenoid, spheroidene, and exchanged with 132-OH-Zn-bacteriochlorophyll a and [3-vinyl]-132-OH-bacteriochlorophyll a at the monomeric, lsquoaccessoryrsquo bacteriochlorophyll sites BA,B or with pheophytin a at the bacteriopheophytin sites HA,B. The primary donor and carotenoid triplet state EPR signals in the temperature range 95–150 K are compared and contrasted with those from native Rb. sphaeroides wild type and Rb. sphaeroides R-26 reaction centers reconstituted with spheroidene. The temperature dependencies of the EPR signals are strikingly different for the various samples. The data prove that triplet energy transfer from the primary donor to the carotenoid is mediated by the monomeric, BChlB molecule. Furthermore, the data show that triplet energy transfer from the primary donor to the carotenoid is an activated process, the efficiency of which correlates with the estimated triplet state energies of the modified pigments

Prolycopene, a Naturally Occurring Stereoisomer of Lycopene

In this paper we record the observation that there occurs in the variety of tomato called "tangerine tomato" a carotenoid, prolycopene, which is an isomer of lycopene; the isomeric relationship is similar to that between lycopene and neolycopene,I and in our opinion prolycopene is to be classed as a naturally occurring neolycopene, being the first observed natural neo form of a C40-carotenoid

Sorghum Carotenoid Variation

Purpose The purpose of this research is to understand the heritability and genetic controls of sorghum grain carotenoids in order to develop a biofortification plan. Hypothesis and Predictions • Hypothesis 1: Carotenoids in a genetically diverse sorghum association panel grown in a temperate humid environment are highly heritable. o Prediction 1: There will be a significant correlation in carotenoid content between sorghum grown in 2015 and 2016 measured by high-performance liquid chromatography (HPLC). o Prediction 2: Genome-wide association studies (GWAS) will identify some of the same quantitative trait loci (QTL) in each year, in particular zeaxanthin epoxidase (ZEP)