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The ARO1 gene of Saccharomyces cerevisiae encodes the arom multifunctional enzyme. Specific inhibitors of amino acid biosynthesis have been used to obtain evidence that expression of a cloned ARO1 gene is regulated in response to amino acid limitation. Northern blot analysis and sequence studies indicate that ARO1 is regulated by the well characterised S. cerevisiae 'general control' mechanism. This provides a very economical means of simultaneously tailoring the synthesis of five shikimate pathway enzymes to the needs of the cell. 相似文献
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R J Truscott J M Marcantonio J Tomlinson G Duncan 《Biochemical and biophysical research communications》1989,162(3):1472-1477
Incubation of intact rat lenses under conditions that stimulated a net influx of calcium resulted in a pronounced loss of transparency and a major decrease in the levels of spectrin. The progressive loss of this cytoskeletal component coincided with the appearance of polypeptides of approximately 150 kDa which showed immunoreactivity with an antibody raised to spectrin. These bands disappeared on further incubation. It is, therefore, suggested that a calcium-activated protease is present in the lens which is capable of degrading spectrin by the initial removal of approximately 90 kDa fragments. This process calcium-induced proteolysis may be the basis for the cytoskeletal reorganisation observed during the differentiation of lens fibre cells and may be involved in cataract development. 相似文献
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Upregulation of bundle sheath electron transport capacity under limiting light in C4 Setaria viridis
Maria Ermakova Chandra Bellasio Duncan Fitzpatrick Robert T. Furbank Fikret Mamedov Susanne von Caemmerer 《The Plant journal : for cell and molecular biology》2021,106(5):1443-1454
C4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO2 concentration at the site of CO2 fixation. C4 plants benefit from high irradiance but their efficiency decreases under shade, causing a loss of productivity in crop canopies. We investigated shade acclimation responses of Setaria viridis, a model monocot of NADP-dependent malic enzyme subtype, focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO2 assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio were enhanced in LL BS cells, indicating a higher capacity for linear electron flow. Abundances of PSI, ATP synthase, Cytochrome b6f and the chloroplast NAD(P)H dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were also increased in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts were associated with a more oxidised plastoquinone pool in LL plants and the formation of PSII – light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results suggest that the supramolecular composition of PSII in BS cells is adjusted according to the redox state of the plastoquinone pool. This discovery contributes to the understanding of the acclimation of PSII activity in C4 plants and will support the development of strategies for crop improvement, including the engineering of C4 photosynthesis into C3 plants. 相似文献
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The-low potential-difference (LPD) cells and the high-potential-difference (HPD) cells ofManduca sexta midgut epithelium have not previously been directly linked with the two major histological cell types, goblet and columnar cells. Using ionophoretic injection of fluorescent dye into LPD and HPD impalement types, we have located the dye-filled cells with the fluorescence microscope, and directly linked the goblet cell with the LPD impalement type and the columnar cell with the HPD impalement type. Thus, for the first time in this polymorphic tissue, the impalement type responsible for active ion transport, the LPD type, has been identified as the goblet cell.Supported in part by USPHS grantr AMR-21890 相似文献