Overexpression of Medicago sativa TMT elevates the α-tocopherol content in Arabidopsis seeds, alfalfa leaves, and delays dark-induced leaf senescence.
Alfalfa (Medicago sativa L.) is a major forage legume for livestock and a target for improving their dietary quality. Vitamin E is an essential vitamin that animals must obtain from their diet for proper growth and development. γ-tocopherol methyltransferase (γ-TMT), which catalyzes the conversion of δ- and γ-tocopherols (or tocotrienols) to β- and α-tocopherols (or tocotrienols), respectively, is the final enzyme involved in the vitamin E biosynthetic pathway. The overexpression of M. sativa L.'s γ-TMT (MsTMT) increased the α-tocopherol content 10-15 fold above that of wild type Arabidopsis seeds without altering the total content of vitamin E. Additionally, in response to osmotic stress, the biomass and the expression levels of several osmotic marker genes were significantly higher in the transgenic lines compared with wild type. Overexpression of MsTMT in alfalfa led to a modest, albeit significant, increase in α-tocopherol in leaves and was also responsible for a delayed leaf senescence phenotype. Additionally, the crude protein content was increased, while the acid and neutral detergent fiber contents were unchanged in these transgenic lines. Thus, increased α-tocopherol content occurred in transgenic alfalfa without compromising the nutritional qualities. The targeted metabolic engineering of vitamin E biosynthesis through MsTMT overexpression provides a promising approach to improve the α-tocopherol content of forage crops.
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Jishan
J
Jiang
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Present address: Animal Husbandry and Veterinary institute, Shanxi Academy of Agricultural Sciences, Taiyuan 030032, China.
Huili
H
Jia
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Present address: Department of Grassland Science, College of Animal Science and Technology, Sichuan Agricultural University, Wenjiang 611130, China.
Guangyan
G
Feng
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Zan
Z
Wang
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Present address: Institute of Grassland Research, Chinese Academy of Agricultural Sciences, Huhhot 010020,China.
Jun
J
Li
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China. Electronic address: gaohongwen@263.net.
Hongwen
H
Gao
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China. Electronic address: wangxuemin@caas.cn.
Xuemin
X
Wang
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D053898:Biosynthetic Pathways / Q000235:genetics; D016922:Cellular Senescence / Q000528:radiation effects; D003624:Darkness; D000455:Medicago sativa / Q000166:cytology / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D010940:Plant Proteins / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D014810:Vitamin E / Q000096:biosynthesis; D024502:alpha-Tocopherol / Q000378:metabolism*
D010940:Plant Proteins; D014810:Vitamin E; D024502:alpha-Tocopherol
Vitamin E; alpha-tocopherol; leaf senescence; osmotic stress tolerance; transgenic alfalfa; γ-tocopherol methyltransferase