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

Partial quantification of pigments extracted from the zooxanthellate octocoral Sinularia flexibilis at varying irradiances

Chlorophyll-a (chl-a) and carotenoid pigments of the zooxanthellate octocoral Sinularia flexibilis were analyzed using high performance liquid chromatography following exposure to three light intensities for over 30 days. From the coral fragments located at different light intensities, a total carotenoid of >41 µg g-1 dry weight, including peridinin, xanthophylls (likely diadinoxanthin + diatoxanthin), and chl-a as the most abundant pigments, with minor contents of astaxantin and ß-carotene were detected. The whole content of chl-a weighed 5 µg g-1 dry weight in all coral colonies. Chl-a and carotenoids contributed 11.2% and 88.2%, respectively, to all pigments detected, and together accounted for 99.4% of the total pigments present. The highest contents of carotenoids and chl-a was observed in the coral grafts placed in an irradiance of 100 µmol quanta m-2 s-1; they showed lower ratios of total carotenoids: chl-a compared to those exposed to 400 µmol quanta m-2 s-1 after >30 days of incubation. The ratios of peridinin and xanthophylls with respect to chl-a from the colonies at 400 µmol quanta m-2 s-1 were approximately double those observed at irradiances of 100 and 200 µmol quanta m-2 s-1. Partial quantification of pigments in this study showed that the carotenoids of S. flexibilis showed a decrease at irradiances above 100 µmol quanta m-2 s-1, with the exception of an increase in ß-carotene at 200 µmol quanta m-2 s-1

CAROTENOIDS CONTENT OF COMMERCIAL SEAWEED IN BALI

In Bali there are several types of seaweed that has long been used as a source of food by people. These seaweed local name are Bulung Boni (Caulerpa spp.) and Bulung Sangu (Gracilaria spp.). However the study of total carotenoids content and types of carotenoids of these seaweed are very limited, therefore need to be further sudy. The types of carotenoids in this study identified based on the retention of value (Rf) on thin layer chromatography. This research concluded that total carotenoids of Bulung Boni (Caulerpa spp.) higher than Bulung Sangu (Gracilaria spp.). Total carotenoids were 57.734 mg / 100 g in Bulung Boni, and 1.776 mg /100 g in Bulung Sangu. The separation of carotenoids Bulung Boni and Bulung Sangu on thin layer chromatography obtained several types of carotenoids. Based on the calculation Rf values on Bulung Boni found as many as nine types of carotenoids such as neoxanthin, astaxanthin free, antheraxanthin ,canthaxanthin ,astaxanthin monoester, fucoxanthin, chlorophyll b, astaxanthin diester, and beta carotene In Bulung Sangu found eight types of carotenoids, such as neoxanthin, violaxanthin, astaxanthin free, antheraxanthin, lutein, chlorophyll b, chlorophyll a, and beta caroten

Recent progress in the identification and determination of freshwater phytoplankton in the natural environment

The biomass of the phytoplankton and its composition is one of the most important factors in water quality control. Determination of the phytoplankton assemblage is usually done by microscopic analysis (Utermöhl's method). Quantitative estimations of the biovolume, by cell counting and cell size measurements, are time-consuming and normally are not done in routine water quality control. Several alternatives have been tried: computer-based image analysis, spectral fluorescence signatures, flow cytometry and pigment fingerprinting aided by high performance liquid chromatography (HPLC). The latter method is based on the fact that each major algal group of taxa contains a specific carotenoid which can be used for identification and relative quantification of the taxa in the total assemblage. This article gives a brief comparative introduction to the different techniques available and presents some recent results obtained by HPLC-based pigment fingerprinting, applied to three lakes of different trophic status. The results show that this technique yields reliable results from different lake types and is a powerful tool for studying the distribution pattern of the phytoplankton community in relation to water depth. However, some restrictions should be taken into account for the interpretation of routine data

Transient expression in Nicotiana benthamiana for rapid functional analysis of genes involved in non-photochemical quenching and carotenoid biosynthesis.

Plants must switch rapidly between light harvesting and photoprotection in response to environmental fluctuations in light intensity. This switch can lead to losses in absorbed energy usage, as photoprotective energy dissipation mechanisms can take minutes to hours to fully relax. One possible way to improve photosynthesis is to engineer these energy dissipation mechanisms (measured as non-photochemical quenching of chlorophyll a fluorescence, NPQ) to induce and relax more quickly, resulting in smaller losses under dynamic light conditions. Previous studies aimed at understanding the enzymes involved in the regulation of NPQ have relied primarily on labor-intensive and time-consuming generation of stable transgenic lines and mutant populations - approaches limited to organisms amenable to genetic manipulation and mapping. To enable rapid functional testing of NPQ-related genes from diverse organisms, we performed Agrobacterium tumefaciens-mediated transient expression assays in Nicotiana benthamiana to test if NPQ kinetics could be modified in fully expanded leaves. By expressing Arabidopsis thaliana genes known to be involved in NPQ, we confirmed the viability of this method for studying dynamic photosynthetic processes. Subsequently, we used naturally occurring variation in photosystem II subunit S, a modulator of NPQ in plants, to explore how differences in amino acid sequence affect NPQ capacity and kinetics. Finally, we functionally characterized four predicted carotenoid biosynthesis genes from the marine algae Nannochloropsis oceanica and Thalassiosira pseudonana and examined the effect of their expression on NPQ in N. benthamiana. This method offers a powerful alternative to traditional gene characterization methods by providing a fast and easy platform for assessing gene function in planta

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

Xanthophylls in light-harvesting complex II of higher plants: light harvesting and triplet quenching

A spectral and functional assignment of the xanthophylls in monomeric and trimeric light-harvesting complex II of green plants has been obtained using HPLC analysis of the pigment composition, laser-flash induced triplet- minus-singlet, fluorescence excitation, and absorption spectra. It is shown that violaxanthin is not present in monomeric preparations, that it has most likely a red-most absorption maximum at 510 nm in the trimeric complex, and that it is involved in both light-harvesting and Chl-triplet quenching. Two xanthophylls (per monomer) have an absorption maximum at 494 nm. These play a major role in both singlet and triplet transfer. These two are most probably the two xanthophylls resolved in the crystal structure, tentatively assigned to lutein, that are close to several chlorophyll molecules [Kuhlbrandt, W., Wang, N., D., and Fujiyoshi, Y. (1994) Nature 367, 614-621]. A last xanthophyll contribution, with an absorption maximum at 486 nm, does not seem to play a significant role in light-harvesting or in Chl-triplet quenching. On the basis of the assumption that the two structurally resolved xanthophylls are lutein, this 486 nm absorbing xanthophyll should be neoxanthin. The measurements demonstrate that violaxanthin is connected to at least one chlorophyll a with an absorption maximum near 670 nm, whereas the xanthophylls absorbing at 494 nm are connected to at least one chlorophyll a with a peak near 675 nm