Age dependent α-tocopherol concentrations in leaves of soybean and pinto beans

Tramontano, William A.; Ganci, David; Pennino, Marianne; Dierenfeld, Ellen S.

doi:10.1016/0031-9422(92)83683-p

Cited by 15 publications

(7 citation statements)

References 9 publications

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“…In contrast, 15 d of growth in the absence of stress increased tocopherol levels in wild-type and 35S::HPT1 leaves less than 2-fold to 0.49 Ϯ 0.04 and 2.00 Ϯ 0.50 nmol cm Ϫ2 leaf area, respectively, most likely as a result of aging. Aging has previously been associated with a moderate increase in leaf tocopherol content in a variety of plants (Rise et al, 1989;Molina-Torres and Martinez, 1991;Tramontano et al, 1992). In 8-weekold plants, the overall increase in total tocopherol levels in stressed relative to non-stressed plants was 18-and 8-fold for wild type and 35S::HPT1, respectively.…”

Section: Biochemical and Physiological Responses Of Wild-type And 35smentioning

confidence: 92%

“…Dry and germinating seeds of many plants accumulate predominantly ␥-tocopherol, whereas ␣-tocopherol is the major tocopherol in leaves, which may reflect distinct roles of individual tocopherols in these tissues (Bramley et al, 2000;Franzen and Haas, 1991;Shintani and DellaPenna, 1998). Significant increases in leaf ␣-tocopherol levels are observed during aging and senescing of plants (Rise et al, 1989;MolinaTorres and Martinez, 1991;Tramontano et al, 1992), possibly to protect cellular components from increased oxidative stress (Munne-Bosch and Alegre, 2002b). Enhanced tocopherol accumulation also occurs in response to a variety of abiotic stresses including high light, drought, salt, and cold and may provide an additional line of protection from oxidative damage (Havaux et al, 2000;Munne-Bosch and Alegre, 2002a).…”

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confidence: 99%

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The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

2003

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Tocopherols are amphipathic antioxidants synthesized exclusively by photosynthetic organisms. Tocopherol levels change significantly during plant growth and development and in response to stress, likely as a consequence of the altered expression of pathway-related genes. Homogentisate phytyltransferase (HPT) is a key enzyme limiting tocopherol biosynthesis in unstressed Arabidopsis leaves (E. Collakova, D. DellaPenna [2003] Plant Physiol 131: 632-642). Wild-type and transgenic Arabidopsis plants constitutively overexpressing HPT (35S::HPT1) were subjected to a combination of abiotic stresses for up to 15 d and tocopherol levels, composition, and expression of several tocopherol pathway-related genes were determined. Abiotic stress resulted in an 18-and 8-fold increase in total tocopherol content in wild-type and 35S::HPT1 leaves, respectively, with tocopherol levels in 35S::HPT1 being 2-to 4-fold higher than wild type at all experimental time points. Increased total tocopherol levels correlated with elevated HPT mRNA levels and HPT specific activity in 35S::HPT1 and wild-type leaves, suggesting that HPT activity limits total tocopherol synthesis during abiotic stress. In addition, substrate availability and expression of pathway enzymes before HPT also contribute to increased tocopherol synthesis during stress. The accumulation of high levels of ␤-, ␥-, and ␦-tocopherols in stressed tissues suggested that the methylation of phytylquinol and tocopherol intermediates limit ␣-tocopherol synthesis. Overexpression of ␥-tocopherol methyltransferase in the 35S::HPT1 background resulted in nearly complete conversion of ␥-and ␦-tocopherols to ␣-and ␤-tocopherols, respectively, indicating that ␥-tocopherol methyltransferase activity limits ␣-tocopherol synthesis in stressed leaves.Tocopherols are a group of lipid soluble antioxidants collectively known as vitamin E that are essential components of animal diets. Dietary vitamin E is required for maintaining proper muscular, immune, and neural function and may be involved in reducing the risk of cancer, cardiovascular disease, and cataracts in humans (Pryor, 2000;Brigelius-Flohe et al., 2002). In plants, tocopherols are believed to protect chloroplast membranes from photooxidation and help to provide an optimal environment for the photosynthetic machinery (Fryer, 1992;Munne-Bosch and Alegre, 2002a). Many of the proposed tocopherol functions in animals and plants are related to their antioxidant properties, the most prominent of which is protection of polyunsaturated fatty acids from lipid peroxidation by quenching and scavenging various reactive oxygen species (ROS) including singlet oxygen, superoxide radicals, and alkyl peroxy radicals (Fukuzawa and Gebicky, 1983;Munne-Bosch and Alegre, 2002a).Tocopherols are only synthesized by photosynthetic organisms and consist of a polar chromanol ring and a 15-carbon lipophilic prenyl chain derived from homogentisic acid (HGA) and phytyl diphosphate (PDP; Fig. 1). In plants, HGA is formed from p-hydroxyphenyl pyruvate (HPP) by the c...

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Section: Biochemical and Physiological Responses Of Wild-type And 35smentioning

confidence: 92%

mentioning

confidence: 99%

The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

2003

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“…It has been shown previously that a moderate increase in leaf tocopherol content is associated with aging in a variety of plants (Rise et al, 1989;MolinaTorres and Martinez, 1991;Tramontano et al, 1992;Lichtenthaler, 2007). To examine whether a similar age-dependent accumulation of tocopherol occurs in C. reinhardtii, wild-type, WT CrVTE2, npq1 lor1, and npq1 lor1 CrVTE2 cells were grown photoautotrophically under LL for up to 15 d and were assayed for their tocopherol content and composition during the continuous growth.…”

Section: Tocopherol Accumulation Is Dependent On the Age Of The Culturementioning

confidence: 99%

Overlapping Photoprotective Function of Vitamin E and Carotenoids inChlamydomonas

Keasling

Niyogi

2011

Plant Physiology

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Tocopherols (vitamin E) and carotenoids are the two most abundant groups of lipid-soluble antioxidants in the chloroplast. Carotenoids are well known for their roles in protecting against photooxidative stress, whereas the photoprotective functions of tocopherols have only recently been examined experimentally. In addition, little is known about the functional overlap of carotenoids and tocopherols in vivo. To investigate this possible overlap, Chlamydomonas reinhardtii strains were engineered to overproduce tocopherols by chloroplast transformation with non-codon-optimized and codon-optimized versions of the homogentisate phytyltransferase vitamin E2 (VTE2) from Synechocystis and by nuclear transformation with VTE2 from C. reinhardtii, which resulted in 1.6-fold, 5-fold to 10-fold, and more than 10-fold increases in total tocopherol content, respectively. To test if tocopherol overproduction can compensate for carotenoid deficiency in terms of antioxidant function, the nuclear VTE2 gene from C. reinhardtii was overexpressed in the npq1 lor1 double mutant, which lacks zeaxanthin and lutein. Following transfer to high light, the npq1 lor1 strains that overaccumulated tocopherols showed increased resistance for up to 2 d and higher efficiency of photosystem II, and they were also much more resistant to other oxidative stresses. These results suggest an overlapping functions of tocopherols and carotenoids in protection against photooxidative stress.

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“…During the early stages of germination the concentration of tocopherol, mostly the α-form, increases in developing primary leaves of monocotyledonous grasses like Triticum vulgare L. [11], Triticum aestivum L., Hordeum vulgare L., Secale cereale L. and Oryza sativa L. (Horvath, unpublished results). In dicots like soybean and pinto beans, an initial increase in α-tocopherol levels seen at the onset of germination was found to be followed by a decline [23,32]. Immature chloroplasts isolated from 2-week-old Spinacia oleracea L. seedlings demonstrate a high tocopherol biosynthetic potential [29].…”

Section: Introductionmentioning

confidence: 99%

Accumulation of tocopherols and tocotrienols during seed development of grape (Vitis vinifera L. cv. Albert Lavallée)

Horváth

Wessjohann

Bigirimana

et al. 2006

Plant Physiology and Biochemistry

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Tocopherols and tocotrienols are present in mature seeds. Yet, little is known about the physiological role and the metabolism of these compounds during seed development. Here we present data on tocopherol and tocotrienol accumulation during seed development in Vitis vinifera L. cv. Albert Lavallée (Royal). This species was chosen for its ability to synthesize both tocopherols and tocotrienols. It is shown here for the first time that during seed development there are significant differences in localization and accumulation kinetics of tocopherols and tocotrienols. Tocopherols are found homogeneously dispersed throughout all tissues of the seed, in concentrations ranging from 20 to 100 μg tocopherol per g dry weight. Tocopherol levels decrease gradually during seed development. In contrast, tocotrienols are only found in the endosperm of the seeds, accumulating in a sigmoid fashion during the maturation period of seed development. Tocotrienol levels were found to be (54 ± 7.4) μg/g dry seed in 90-day-old seeds of V. vinifera L. Furthermore, tocotrienol biosynthesis is demonstrated in these seeds during tocotrienol accumulation and in an endosperm fraction isolated at 75 days after flowering.

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Age dependent α-tocopherol concentrations in leaves of soybean and pinto beans

Cited by 15 publications

References 9 publications

The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

Overlapping Photoprotective Function of Vitamin E and Carotenoids inChlamydomonas

Accumulation of tocopherols and tocotrienols during seed development of grape (Vitis vinifera L. cv. Albert Lavallée)

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