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71.
We define the photoresponsiveness, during seedling de-etiolation,of PHYTOCHROME-INTERACTING FACTOR 3-LIKE 1 (PIL1), initiallyidentified by microarray analysis as an early-response genethat is robustly repressed by first exposure to light. We showthat PIL1 mRNA abundance declines rapidly, with a half-timeof 15 min, to a new steady-state level, 10-fold below the initialdark level, within 45 min of first exposure to red light. Analysisof phy-null mutants indicates that multiple phytochromes, includingphyA and phyB, impose this repression. Conversely, PIL1 expressionis rapidly derepressed by subsequent far-red irradiation ofpreviously red light-exposed seedlings. However, the magnitudeof this derepression is modulated over time, in a biphasic manner,in response to increasing duration of pre-exposure to continuousred light: (i) an early phase (up to about 6 h) of relativelyrapidly increasing effectiveness of far-red reversal of repression,as declining phyA levels relieve initial very low fluence suppressionof this response; and (ii) a second phase (beyond 6 h) of graduallydeclining effectiveness of far-red reversal, to only 20% ofmaximal derepression, within 36 h of continuous red light exposure,with no evidence of circadian modulation of this responsiveness,an observation in striking contrast to a previous report forentrained, green seedlings exposed to vegetative shade. Thesedata, together with analysis of phytochrome signaling mutantsand overexpressors with aberrant de-etiolation phenotypes, suggestthat the second-phase decline in robustness of PIL1 derepressionis an indirect consequence of the global developmental transitionfrom the etiolated to the de-etiolated state, and that circadiancoupling of derepression requires entrainment. 相似文献
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Pedras MS Erosa-López CC Quail JW Taylor JL 《Bioorganic & medicinal chemistry letters》1999,9(23):3291-3294
The chemical structure and bioactivity of phomalairdenone (7), a new sesquiterpenic host-selective phytotoxin produced by an unusual virulent type isolate of the blackleg fungus [Phoma lingam, perfect stage Leptosphaeria maculans (Desm.) Ces. et de Not.] are reported. 相似文献
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Daniel T. Baran John M. Quail Rahul Ray Thomas Honeyman 《Journal of cellular biochemistry》2001,80(2):259-265
We have recently reported that annexin II serves as a membrane receptor for 1α,25‐(OH)2D3 and mediates the rapid effect of the hormone on intracellular calcium. The purpose of these studies was to characterize the binding of the hormone to annexin II, determine the specificity of binding, and assess the effect of calcium on binding. The binding of [14C]‐1α,25‐(OH)2D3 bromoacetate to purified annexin II was inhibited by 1α,25‐(OH)2D3 in a concentration‐dependent manner. Binding of the radiolabeled ligand to annexin II was markedly diminished by 1α,25‐(OH)2D3 at 24 μM, 18 μM, and 12 μM and blunted by 6 μM and 3 μM. At a concentration of 12 μM, 1β,25‐(OH)2D3 also diminished the binding of [14C]‐1α,25‐(OH)2D3 bromoacetate to annexin II, but cholecalciferol, 25‐(OH)D3, and 24,25‐(OH)2D3 did not. Saturation analyses of the binding of [3H]‐1α,25‐(OH)2D3 to purified annexin II showed a KD of 5.5 × 10−9 M, whereas [3H]‐1β,25‐(OH)2D3 exhibited a KD of 6.0 × 10−9 M. Calcium, which binds to the carboxy terminal domain of annexin II, had a concentration‐dependent effect on [14C]‐1α,25‐(OH)2D3 bromoacetate binding to annexin II, with 600 nM calcium being able to inhibit binding of the radiolabeled analog. The inhibitory effect of calcium was prevented by EDTA. Homocysteine, which binds to the amino terminal domain of annexin II, had no effect on the binding of the bromoacetate analog to the protein. The data indicate that 1α,25‐(OH)2D3 binding to annexin II is specific and suggest that the binding site may be located on the carboxy terminal domain of the protein. The ability of 1β,25‐(OH)2D3 to inhibit the binding of [14C]‐1α,25(OH)2D3 bromoacetate to annexin II provides a biochemical explanation for the ability of the 1β‐epimer to inhibit the rapid actions of the hormone in vitro. J. Cell. Biochem. 80:259–265, 2000. © 2000 Wiley‐Liss, Inc. 相似文献
75.
The phytochrome A-specific signaling intermediate SPA1 interacts directly with COP1, a constitutive repressor of light signaling in Arabidopsis. 总被引:14,自引:0,他引:14
SPA1 is a phytochrome A (phyA)-specific signaling intermediate that acts as a light-dependent repressor of photomorphogenesis in Arabidopsis seedlings. It contains a WD-repeat domain that shows high sequence similarity to the WD-repeat region of the constitutive repressor of light signaling, COP1. Here, using yeast two-hybrid and in vitro interaction assays, we show that SPA1 strongly and selectively binds to COP1. Domain mapping studies indicate that the putative coiled-coil domain of SPA1 is necessary and sufficient for binding to COP1. Conversely, similar deletion analyses of the COP1 protein suggest that SPA1 interacts with the presumed coiled-coil domain of COP1. To further investigate SPA1 function in the phyA signaling pathway, we tested whether SPA1, like COP1, mediates changes in gene expression in response to light. We show that spa1 mutations increase the photoresponsiveness of certain light-regulated genes within 2 h of light treatment. Taken together, the results suggest that SPA1 may function to link the phytochrome A-specific branch of the light signaling pathway to COP1. Hence, our data provide molecular support for the hypothesis that COP1 is a convergence point for upstream signaling pathways dedicated to individual photoreceptors. 相似文献
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A number of spraying experiments showed that the virus cannot enter a plant unless some of the cells are injured. It is not essential that such injury should be brought about in the presence of the virus. The chances of infection fall off rapidly in the first few minutes after injury, but infection occurs occasionally as long as half an hour after the cell is damaged.
Inoculations by micropipette into single cells of the host plant yielded only about one-tenth of the expected number of infections. This suggests differences in the susceptibility of the cells to virus attack. 相似文献
Inoculations by micropipette into single cells of the host plant yielded only about one-tenth of the expected number of infections. This suggests differences in the susceptibility of the cells to virus attack. 相似文献
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