Are there Specific In Vivo Roles for alpha- and gamma-Tocopherol in Plants?
Tocopherols belong to the Vitamin E family of amphiphilic antioxidants, together with the subfamily of tocotrienols. They are exclusively synthesized by photosynthetic organisms and consist of a polar chromanol head group and a lipophilic prenyl tail.The Vitamin E pool in dicots is commonly dominated by alpha-tocopherol in leaves and by gamma-tocopherol in seeds. This observation rises the question, whether alpha-tocopherol and gamma-tocopherol are functionally equivalent in protection against various kinds of oxidative stress in planta: superoxide and singlet oxygen evolution are high during oxygenic photosynthesis in leaves, while polyunsaturated fatty acid oxidation is the main target for tocopherols in seeds.We found that transgenic tobacco plants with a substitution of gamma- for alpha-tocopherol in leaves are more tolerant than the wild type towards sorbitol and methyl viologen mediated oxidative stress, which increase lipid peroxidation in the chloroplast stroma. This suggests that gamma-tocopherol is more potent than alpha-tocopherol in protecting against lipid peroxidation in both, seeds and leaves, although its natural abundance is in seeds only. If so, why has alpha-tocopherol accumulation in leaves been favoured during the evolution of land plants and does the abundance of gamma-tocopherol in leaves conceal a disadvantage for plant fitness?
Voll
Lars M
LM
Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen, Germany.
Abbasi
Ali-Reza
AR
Plant Physiol. 2004 Jul;135(3):1256-68
15247386
Plant Cell Rep. 2007 Jan;26(1):61-70
16909228
J Agric Food Chem. 2003 Jul 2;51(14):3940-4
12822927
Plant Physiol. 2003 Oct;133(2):930-40
14512521
Plant Physiol. 2005 Feb;137(2):713-23
15665245
Plant Physiol. 2007 Apr;143(4):1720-38
17293434
Plant Cell. 2005 Jul;17(7):1866-75
15987996
J Agric Food Chem. 2001 Oct;49(10):4990-4
11600056
J Exp Bot. 2006;57(8):1677-84
16714305
Curr Opin Cell Biol. 2001 Aug;13(4):399-404
11454443
Plant Cell. 2005 Dec;17(12):3451-69
16258032
Plant Cell. 2003 Dec;15(12):3007-19
14630966
Plant Cell Environ. 2006 May;29(5):879-87
17087471
Acc Chem Res. 2007 Apr;40(4):251-7
17269797
FEBS Lett. 2003 Apr 10;540(1-3):35-40
12681479
Plant Mol Biol. 2003 Aug;52(6):1181-90
14682617
Plant Physiol. 2003 Feb;131(2):632-42
12586887
Planta. 2003 Nov;218(1):1-14
14513379
Trends Plant Sci. 2004 Oct;9(10):490-8
15465684
Curr Opin Plant Biol. 2002 Jun;5(3):230-6
11960741
Annu Rev Plant Physiol Plant Mol Biol. 1999 Jun;50:133-161
15012206
Plant Cell. 2006 Dec;18(12):3706-20
17194769
J Plant Physiol. 2005 Jul;162(7):749-57
16008099
J Phys Chem B. 2006 Jun 15;110(23):11540-8
16771430