title: Specific roles of tocopherols and tocotrienols in seed longevity and germination tolerance to abiotic stress in transgenic rice.
abstract: Tocopherols and tocotrienols are lipophilic antioxidants that are abundant in plant seeds. Although their roles have been extensively studied, our understanding of their functions in rice seeds is still limited. In this study, on the basis of available RNAi rice plants constitutively silenced for homogentisate phytyltransferase (HPT) and tocopherol cyclase (TC), we developed transgenic plants that silenced homogentisate geranylgeranyl transferase (HGGT). All the RNAi plants showed significantly reduced germination percentages and a higher proportion of abnormal seedlings than the control plants, with HGGT transgenics showing the most severe phenotype. The accelerated aging phenotype corresponded well with the amount of H2O2 accumulated in the embryo, glucose level, and ion leakage, but not with the amount of O(2-) accumulated in the embryo and lipid hydroperoxides levels in these genotypes. Under abiotic stress conditions, HPT and TC transgenics showed lower germination percentage and seedling growth than HGGT transgenics, while HGGT transgenics showed almost the same status as the wild type. Therefore, we proposed that tocopherols in the germ may protect the embryo from reactive oxygen species under both accelerated aging and stress conditions, whereas tocotrienols in the pericarp may exclusively help in reducing the metabolic activity of the seed during accelerated aging.
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Defu
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yanlan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Fang
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Shi
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China. Electronic address: xiwenchen@nankai.edu.cn.
authors.forename: Xiwen
authors.initials: X
authors.lastname: Chen
mesh_terms: D018525:Germination; D012275:Oryza / Q000196:embryology / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000502:physiology*; D012639:Seeds / Q000502:physiology*; D013312:Stress, Physiological; D024505:Tocopherols / Q000378:metabolism*; D024508:Tocotrienols / Q000378:metabolism*
chemical_list: D024508:Tocotrienols; D024505:Tocopherols
keywords: Function; Longevity; Rice (Oryza sativa); Seed; Tocopherols; Tocotrienols