Lutein ester profile in wheat and tritordeum can be modulated by temperature: Evidences for regioselectivity and fatty acid preferential of enzymes encoded by genes on chromosomes 7D and 7Hch

Durum Wheat at Risk in a Climate Change Scenario: The Carotenoid Content is Affected by Short Heat Waves

Short heat waves (SHW), defined as periods of several consecutive days with high temperatures above the developmental optimum, will become more frequent due to climate change. The impact of SHW on yield and yield-related parameters has received considerable interest, but their effects on grain quality remain poorly understood. We employed a simulation approach to investigate the impact of SHW on durum wheat quality over a 7 day period, starting 1 week after anthesis. During the SHW treatment, carried out using portable polyethylene tents, the temperature in the treated plots increased by 10-15 °C during daily hours. The SHW treatment reduced the number of grains per spike, thousand kernel weight, and total carotenoid content in grains in stressed plants in comparison to control plants. However, no differences in the protein content or percentage of vitreous grains were observed. The behavior of individual carotenoids in response to SHW appears to differ, suggesting a differential change in the balance between β,ε- and β,β-branches of the carotenoid biosynthetic pathway as a consequence of SHW-induced stress. The present study highlights the importance of developing efficient breeding strategies for reduced sensitivities to heat stress. Such strategies should not only prioritize yield but also encompass grain quality.

Mediation of a GDSL Esterase/Lipase in Carotenoid Esterification in Tritordeum Suggests a Common Mechanism of Carotenoid Esterification in Triticeae Species

Carotenoids are essential in human diet, so that the development of programs toward carotenoid enhancement has been promoted in several crops. The cereal tritordeum, the amphiploid derived from the cross between Hordeum chilense Roem. et Schulz. and durum wheat has a remarkable carotenoid content in the endosperm. Besides, a high proportion of these carotenoids are esterified with fatty acids. The identification of the gene(s) responsible for xanthophyll esterification would be useful for breeding as esterified carotenoids show an increased ability to accumulate within plant cells and have a higher stability during post-harvest storage. In this work, we analyzed five genes identified as candidates for coding the xanthophyll acyltransferase (XAT) enzyme responsible for lutein esterification in H. chilense genome. All these genes were expressed during grain development in tritordeum, but only HORCH7HG021460 was highly upregulated. Sequence analysis of HORCH7HG021460 revealed a G-to-T transversion, causing a Glycine to Cysteine substitution in the protein of H290 (the only accession not producing quantifiable amounts of lutein esters, hereinafter referred as zero-ester) of H. chilense compared to the esterifying genotypes. An allele-specific marker was designed for the SNP detection in the H. chilense diversity panel. From the 93 accessions, only H290 showed the T allele and the zero-ester phenotype. Furthermore, HORCH7HG021460 is the orthologue of XAT-7D, which encodes a XAT enzyme responsible for carotenoid esterification in wheat. Thus, HORCH7HG021460 (XAT-7Hch) is a strong candidate for lutein esterification in H. chilense and tritordeum, suggesting a common mechanism of carotenoid esterification in Triticeae species. The transference of XAT-7Hch to wheat may be useful for the enhancement of lutein esters in biofortification programs.

Carotenoid content of extruded and puffed products made of colored-grain wheats

Wheat is a relevant source not only of essential macronutrients but also of many other health-promoting phytochemicals (carotenoids, anthocyanins, tocols, phenolic acids, etc.). Colored-grain wheats were used for extrusion and kernel puffing. The total content of carotenoids (sum of lutein, zeaxanthin, antheraxanthin, α- and β-carotene, and xanthophyll esters) decreased significantly due to extrusion (to 25.7%) and puffing (to 31.6%), compared to the content in the raw material. Zeaxanthin was shown to be the most stable among all detected carotenoids (30.8 and 48.7% was preserved). The results of the performed analyses have not confirmed greater stability of xanthophyll esters against higher temperatures (decrease to 29.5 and 22.1%). Both technologies induced E-to Z-isomerization of all-E-lutein and puffing also of all-E-zeaxanthin. Higher concentrations of 13-Z- and 9-Z-zeaxanthin were identified in puffed grains (2× and 37× on average). To preserve more carotenoids, it is appropriate to look for a more suitable food processing technology.

A Routine Method for the Extraction and HPLC-DAD Profiling of Major Plant and Food Carotenoids

Carotenoids are ubiquitously present in Nature, and especially in plants and derived foods. The carotenoid profiling is necessary to understand relevant aspects in relation to their biochemistry and genetics, as well as their important roles on human health and animal ecophysiology. Here we propose a simple methodology for the routine extraction and efficient HPLC separation of the most common plant and food carotenoids from plant and animal origins.

Carotenoid content in tritordeum is not primarily associated with esterification during grain development

Tritordeums show a significant proportion of lutein esters which increases carotenoid stability and retention throughout the food chain. Esterification is a common means of carotenoid sequestration. A putative association between lutein esters formation acting as a metabolic sink during early stages of grain development and the high carotenoid content of tritordeums is analyzed in this work. Compared to wheat, tritordeums accumulated significantly higher lutein contents from 20 days post anthesis (dpa) but lutein esters were not detected until 36 dpa. Thus esterification is not acting as a metabolific sink before 36 dpa. The presence of lutein esters at late stages of grain development may have a complementary role in carotenoid accumulation by reducing and/or counteracting their catabolism. The differences for lutein esterification among tritordeums suggest the existence of diversity for xanthophyll acyl transferases that could be exploited to increase lutein retention in this cereal and through the food chain.

Lutein Esterification in Wheat Flour Increases the Carotenoid Retention and Is Induced by Storage Temperatures

The present study aimed to evaluate the effects of long-term storage on the carotenoid pigments present in whole-grain flours prepared from durum wheat and tritordeum. As expected, higher storage temperatures showed a catabolic effect, which was very marked for free carotenoid pigments. Surprisingly, for both cereal genotypes, the thermal conditions favoured the synthesis of lutein esters, leading to an enhanced stability, slower degradation, and, subsequently, a greater carotenoid retention. The putative involvement of lipase enzymes in lutein esterification in flours is discussed, particularly regarding the preferential esterification of the hydroxyl group with linoleic acid at the 3' in the ε-ring of the lutein molecule. The negative effects of processing on carotenoid retention were less pronounced in durum wheat flours, which could be due to an increased esterifying activity (the de novo formation of diesterified xanthophylls was observed). Moreover, clear differences were observed for tritordeum depending on whether the lutein was in a free or esterified state. For instance, lutein-3'-O-monolinoleate showed a three-fold lower degradation rate than free lutein at 37 °C. In view of our results, we advise that the biofortification research aimed at increasing the carotenoid contents in cereals should be based on the selection of varieties with an enhanced content of esterified xanthophylls.

Free and esterified carotenoids in pigmented wheat, tritordeum and barley grains

Carotenoids are important phytonutrients responsible for the yellow endosperm color in cereal grains. Five carotenoids, namely lutein, zeaxanthin, antheraxanthin, α- and β-carotene, were quantified by HPLC-DAD-MS in fourteen genotypes of wheat, barley and tritordeum harvested in Czechia in 2014 and 2015. The highest carotenoid contents were found in yellow-grained tritordeum HT 439 (12.16μg/gDW), followed by blue-grained wheat V1-131-15 (7.46μg/gDW), and yellow-grained wheat TA 4024 (7.04μg/gDW). Comparing carotenoid contents, blue varieties had lower whereas purple ones had the same or higher levels than conventional bread wheat. Lutein was the main carotenoid found in wheat and tritordeum while zeaxanthin dominated in barley. The majority of cereals contained considerable levels of esterified forms (up to 61%) of which lutein esters prevailed. It was assessed that cereal genotype determines the proportion of free and esterified forms. High temperatures and drought during the growing season promoted carotenoid biosynthesis.

Identification and quantitative analysis of β-cryptoxanthin and β-citraurin esters in Satsuma mandarin fruit during the ripening process

In this study, to investigate the xanthophyll accumulation in citrus fruits, the major fatty acid esters of β-cryptoxanthin and β-citraurin were identified, and changes in their contents were investigated in two Satsuma mandarin varieties, 'Miyagawa-wase' and 'Yamashitabeni-wase', during the ripening process. The results showed that β-cryptoxanthin and β-citraurin were mainly esterified with lauric acid, myristic acid, and palmitic acid in citrus fruits. During the ripening process, β-cryptoxanthin laurate, myristate, and palmitate were accumulated gradually in the flavedos and juice sacs of the two varieties. In the flavedo of 'Yamashitabeni-wase', β-citraurin laurate, myristate, and palmitate were specifically accumulated, and their contents increased rapidly with a peak in November. In addition, functional analyses showed that CitCCD1 and CitCCD4 efficiently cleaved the free β-cryptoxanthin, but not the β-cryptoxanthin esters in vitro. The substrate specificity of CitCCDs towards free β-cryptoxanthin indicated that β-cryptoxanthin esters might be more stable than free β-cryptoxanthin in citrus fruits.