Ascorbate is the major water-soluble antioxidant in plants and animals, and it is an essential nu... more Ascorbate is the major water-soluble antioxidant in plants and animals, and it is an essential nutrient for most insect herbivores. Therefore, ascorbate oxidase (AO) has been proposed to function as a plant defense that decreases the availability of ascorbate to insects. This hypothesis was tested by producing transgenic poplar (Populus tremula × Populus alba; Salicaceae) with 14- to 37-fold higher foliar AO activities than control (wild type) leaves and feeding these leaves to Lymantria dispar L. (Lepidoptera: Lymantriidae) caterpillars and Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) grasshoppers. To examine potential mechanisms of activity of AO in these insects, ascorbyl radical and/or ascorbate levels were measured in gut contents. No significant changes in ascorbyl radical or ascorbate levels were found in the midgut contents of L. dispar larvae that ingested the leaves of the AO-overexpressing genotypes compared to the control genotype, and no significant decreases in ascorbate levels were found in the foregut or midgut contents of M. sanguinipes. Treatment of control leaves with commercial AO also produced no changes in the midgut biochemistry of L. dispar larvae, as measured by levels of ascorbyl radicals. Likewise, no increase in oxidative stress was observed in L. dispar that consumed tannin-treated AO-overexpressing leaves compared with tannin-treated control genotype leaves. Performance experiments were carried out on first- and fourth-instar L. dispar larvae on leaf disks and on third instars feeding on intact leaves on trees. In no case was a significant difference found in the contrast between the control and three AO-overexpressing genotypes for relative consumption rate, relative growth rate, or nutritional indices. We conclude that elevated levels of AO in poplar are unlikely to serve as a defense against herbivores such as L. dispar or M. sanguinipes and that the low oxygen levels commonly found in the guts of caterpillars and grasshoppers may limit the activity of ingested AO in these leaf-chewing insects.
Proceedings of The National Academy of Sciences, 2002
We report here the striking anisotropy of fluorescence exhibited by crystals of native green fluo... more We report here the striking anisotropy of fluorescence exhibited by crystals of native green fluorescence protein (GFP). The crystals were generated by water dialysis of highly purified GFP obtained from the jellyfish Aequorea. We find that the fluorescence becomes six times brighter when the excitation, or emission, beam is polarized parallel (compared with perpendicular) to the crystal long axis. Thus, the major dipoles of the fluorophores must be oriented very nearly parallel to the crystal long axis. Observed in a polarizing microscope between parallel polars instead of either a polarizer or analyzer alone, the fluorescence polarization ratio rises to an unexpectedly high value of about 30:1, nearly the product of the fluorescence excitation and emission ratios, suggesting a sensitive method for measuring fluorophore orientations, even of a single fluorophore molecule. We have derived equations that accurately describe the relative fluorescence intensities of crystals oriented in various directions, with the polarizer and analyzer arranged in different configurations. The equations yield relative absorption and fluorescence coefficients for the four transition dipoles involved. Finally, we propose a model in which the elongated crystal is made of GFP molecules that are tilted 60° to align the fluorophores parallel to the crystal long axis. The unit layer in the model may well correspond to the arrangement of functional GFP molecules, to which resonant energy is efficiently transmitted from Ca2+-activated aequorin, in the jellyfish photophores.
Để phát triển và tăng khả năng cạnh tranh, ngành Dệt May Việt Nam đang xác định hướng dịch chuyển... more Để phát triển và tăng khả năng cạnh tranh, ngành Dệt May Việt Nam đang xác định hướng dịch chuyển của ngành trong chuỗi giá trị toàn cầu theo hướng thời trangcông nghệthương hiệu. Để đáp ứng yêu cầu dịch chuyển và mục tiêu phát triển bền vững, ngành Dệt May cần có nguồn nhân lực chất lượng cao. Trên cơ sở phân tích các đặc điểm của nguồn nhân lực Ngành Dệt May, đề xuất những định hướng để Ngành Dệt May chủ động trong hoạt động đào tạo phát triển nguồn nhân lực và xây dựng liên kết bền vững với các cơ sở đào tạo dệt may, đảm bảo cho ngành có được nguồn nhân lực ổn định và đáp ứng yêu cầu.
Ascorbate is the major water-soluble antioxidant in plants and animals, and it is an essential nu... more Ascorbate is the major water-soluble antioxidant in plants and animals, and it is an essential nutrient for most insect herbivores. Therefore, ascorbate oxidase (AO) has been proposed to function as a plant defense that decreases the availability of ascorbate to insects. This hypothesis was tested by producing transgenic poplar (Populus tremula × Populus alba; Salicaceae) with 14- to 37-fold higher foliar AO activities than control (wild type) leaves and feeding these leaves to Lymantria dispar L. (Lepidoptera: Lymantriidae) caterpillars and Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) grasshoppers. To examine potential mechanisms of activity of AO in these insects, ascorbyl radical and/or ascorbate levels were measured in gut contents. No significant changes in ascorbyl radical or ascorbate levels were found in the midgut contents of L. dispar larvae that ingested the leaves of the AO-overexpressing genotypes compared to the control genotype, and no significant decreases in ascorbate levels were found in the foregut or midgut contents of M. sanguinipes. Treatment of control leaves with commercial AO also produced no changes in the midgut biochemistry of L. dispar larvae, as measured by levels of ascorbyl radicals. Likewise, no increase in oxidative stress was observed in L. dispar that consumed tannin-treated AO-overexpressing leaves compared with tannin-treated control genotype leaves. Performance experiments were carried out on first- and fourth-instar L. dispar larvae on leaf disks and on third instars feeding on intact leaves on trees. In no case was a significant difference found in the contrast between the control and three AO-overexpressing genotypes for relative consumption rate, relative growth rate, or nutritional indices. We conclude that elevated levels of AO in poplar are unlikely to serve as a defense against herbivores such as L. dispar or M. sanguinipes and that the low oxygen levels commonly found in the guts of caterpillars and grasshoppers may limit the activity of ingested AO in these leaf-chewing insects.
Proceedings of The National Academy of Sciences, 2002
We report here the striking anisotropy of fluorescence exhibited by crystals of native green fluo... more We report here the striking anisotropy of fluorescence exhibited by crystals of native green fluorescence protein (GFP). The crystals were generated by water dialysis of highly purified GFP obtained from the jellyfish Aequorea. We find that the fluorescence becomes six times brighter when the excitation, or emission, beam is polarized parallel (compared with perpendicular) to the crystal long axis. Thus, the major dipoles of the fluorophores must be oriented very nearly parallel to the crystal long axis. Observed in a polarizing microscope between parallel polars instead of either a polarizer or analyzer alone, the fluorescence polarization ratio rises to an unexpectedly high value of about 30:1, nearly the product of the fluorescence excitation and emission ratios, suggesting a sensitive method for measuring fluorophore orientations, even of a single fluorophore molecule. We have derived equations that accurately describe the relative fluorescence intensities of crystals oriented in various directions, with the polarizer and analyzer arranged in different configurations. The equations yield relative absorption and fluorescence coefficients for the four transition dipoles involved. Finally, we propose a model in which the elongated crystal is made of GFP molecules that are tilted 60° to align the fluorophores parallel to the crystal long axis. The unit layer in the model may well correspond to the arrangement of functional GFP molecules, to which resonant energy is efficiently transmitted from Ca2+-activated aequorin, in the jellyfish photophores.
Để phát triển và tăng khả năng cạnh tranh, ngành Dệt May Việt Nam đang xác định hướng dịch chuyển... more Để phát triển và tăng khả năng cạnh tranh, ngành Dệt May Việt Nam đang xác định hướng dịch chuyển của ngành trong chuỗi giá trị toàn cầu theo hướng thời trangcông nghệthương hiệu. Để đáp ứng yêu cầu dịch chuyển và mục tiêu phát triển bền vững, ngành Dệt May cần có nguồn nhân lực chất lượng cao. Trên cơ sở phân tích các đặc điểm của nguồn nhân lực Ngành Dệt May, đề xuất những định hướng để Ngành Dệt May chủ động trong hoạt động đào tạo phát triển nguồn nhân lực và xây dựng liên kết bền vững với các cơ sở đào tạo dệt may, đảm bảo cho ngành có được nguồn nhân lực ổn định và đáp ứng yêu cầu.
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