排序方式: 共有40条查询结果,搜索用时 15 毫秒
1.
The in situ localization of Ca2+ in stage I sporangiophores of the fungus Phycomyces blakesleeanus was achieved with the potassium pyroantimonate technique. Precipitates of calcium-antimonate were present in mitochondria, vacuoles, endoplasmic reticulum and adjacent cytoplasm, Golgi-like bodies, and nuclei but not cell walls. Material treated with the calcium chelator EGTA lacked these precipitates. The preferential localization of Ca2+ in mitochondria, endoplasmic reticulum and vacuoles suggests that these organelles modulate the level of this cation in sporangiophores of P. blakesleeanus.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethyl ether) N,N, tetraacetic acid 相似文献
2.
3.
The absolute sensitivity of sporangiophores of Phycomyces blakesleeanus to centrifugal acceleration was determined on a clinostat centrifuge. The centrifuge provides centrifugal accelerations ranging from 10(-4) to 6 x g. The rotor of the centrifuge, which accommodates 96 culture vials with single sporangiophores, is clinostatted, that is, turning "head over", at slow speed (1 rev min(-1)) while it is running. The negative gravitropism of sporangiophores is characterized by two components: a polar angle, which is measured in the plane of bending, and an aiming-error angle, which indicates the deviation of the plane of bending from the vector of the centrifugal acceleration. Dose-response curves were generated for both angles with centrifugations lasting 3, 5, and 8 h. The threshold for the polar angle depends on the presence of statoliths, so-called octahedral protein crystals in the vacuoles. The albino strain C171 carAcarR (with crystals) has a threshold near 10(-2) x g while the albino strain C2 carAgeo-3 (without crystals) has a threshold of about 2 x 10(-1) x g. The threshold for the aiming error angle is ill defined and is between 10(-2) and 10(-1) x g. The threshold for the polar angle of the wild type NRRL 1555 (with crystals) is near 8 x 10(-2) x g. 相似文献
4.
David Weinkove Juan Angel Poyatos Heribert Greiner Enrique Oltra Javier Avalos Leonid Fukshansky Alejandro F. Barrero Enrique Cerdá-Olmedo 《Fungal genetics and biology : FG & B》1998,25(3):196-203
Weinkove, D., Poyatos, J. A., Greiner, H., Oltra, E., Avalos, J., Fukshansky, L., Barrero, A. F., and Cerdá-Olmedo, E. 1998. Mutants ofPhycomyceswith decreased gallic acid content.Fungal Genetics and Biology25, 196–203. Most plants and some fungi accumulate phenols. Two hydroxybenzoic acids, gallic and protocatechuic acids, are abundant in the giant sporangiophores of the zygomycetePhycomyces blakesleeanus,much more so than in the basal mycelium or the culture medium. The actual concentrations vary with illumination, age of the culture, and composition of the medium. We devised a simple screening procedure to isolatehbamutants whose sporangiophores contained less gallic acid than the wild type. The most useful mutant had very low concentrations of hydroxybenzoic acids in the sporangiophores, but about the same as the wild type in the basal mycelium and the medium. The mutant was only slightly different from the wild type in growth and morphology. Mutant and wild-type sporangiophores grew away from ultraviolet C sources (260 nm) equally well. Contrary to previous conjectures, ultraviolet tropism does not depend on the ultraviolet absorption of gallic acid or other free hydroxybenzoic acids in the sporangiophore. Against expectations, phenols did not impair DNA extraction: sporangiophores produced better DNA preparations than basal mycelia and thehbamutant only slightly better than the wild type. 相似文献
5.
Governing equations for plant cell growth 总被引:2,自引:0,他引:2
Joseph K. E. Ortega 《Physiologia plantarum》1990,79(1):116-121
6.
Abstract A glycerol:NADP+ 2-oxidoreductase was purified to homogeneity from Phycomyces blakesleeanus sporangiospores. The enzyme had an M r of 34 000–39 000 and consisted of a single polypeptide. It had a pH optimum between 6–6.5 and a K m of 3.9 mM for dihydroxyacetone. The reverse reaction had a pH optimum of 9.4 and a K m for glycerol of more than 2 M. The enzyme was completely specific for NADPH ( K m = 0.01 mM) or NADP+ ( K m = 0.17 mM) and greatly preferred dihydroxyacetone over glyceraldehyde as substrate. Besides glycerol, l -arabitol and mesoerythritol were also oxidized by the enzyme. It was inhibited by ionic strengths in excess of 100 mM and is probably involved in the synthesis of glycerol during early spore germination. 相似文献
7.
8.
To elucidate the graviperception of the unicellular fungus, Phycomycesblakesleeanus, sporangiophores were inspected for intracellular structures which relocate with respect to gravity. Two structures, paracrystalline
proteins (so-called octahedral crystals) and an aggregate of lipid globules, were identified which showed redistribution upon
reorientation of the sporangiophore. Octahedral crystals occur throughout the sporangiophore, including the apical growing
zone, and are localized inside vacuoles in which they reside singly or in clusters of up to 40 loosely associated individuals.
Upon a 90° reorientation of sporangiophores, crystal clusters sedimented in approximately 50–200 s from the upper to the lower
side, corresponding to a speed of 0.5–2 μm s−1. Stage-4 sporangiophores (with sporangium) of three mutants which lack the crystals displayed anormal kinetics of gravitropism
and substantially reduced bending angles in comparison to sporangiophores of the wild type. While horizontally placed wild-type
sporangiophores reached the vertical position after 10–12 h, the crystal-lacking mutants bent maximally 40°–50° upward. In
stage-1 sporangiophores a conspicuous aggregate of lipid globules is positioned about 50 μm below the apex. The globules floated
upwards when the sporangiophore was placed horizontally forming in this way a cap-like aggregate. It is proposed that both
the sedimenting protein crystals and the upward-floating globules are involved in gravisensing.
Received: 23 March 1999 / Accepted: 27 May 1999 相似文献
9.
Phycomyces blakesleeanus isocitrate lyase (EC 4.1.3.1) is in vivo reversibly inactivated by hydrogen peroxide. The purified enzyme showed reversible inactivation by an ascorbate plus Fe(2+) system under aerobic conditions. Inactivation requires hydrogen peroxide; was prevented by catalase, EDTA, Mg(2+), isocitrate, GSH, DTT, or cysteine; and was reversed by thiols. The ascorbate served as a source of hydrogen peroxide and also reduced the Fe(3+) ions produced in a "site-specific" Fenton reaction. Two redox-active cysteine residues per enzyme subunit are targets of oxidative modification; one of them is located at the catalytic site and the other at the metal regulatory site. The oxidized enzyme showed covalent and conformational changes that led to inactivation, decreased thermal stability, and also increased inactivation by trypsin. These results represent an example of redox regulation of an enzymatic activity, which may play a role as a sensor of redox cellular status. 相似文献
10.
Phototropism experiments were done with sporangiophores of the fungus Phycomyces blakesleeanus to characterize the interaction between far-UV, blue and red light. Far-UV light elicits negative phototropism (bending away
from the light source) while blue light elicits positive phototropism (bending toward the light source). In contrast, red
light above 600 nm is phototropically inert. Phototropism was analyzed with light regimens of bilateral or unilateral irradiation
with far-UV and blue light. Under bilateral irradiation, in which the two light sources were facing each other, blue light
partially inhibited the far-UV-elicited phototropism. A fluence-response curve for this inhibition showed that blue light
was maximally effective at fluence rates which exceeded 3 to 57 times that of the far-UV. Tonic red light, which was given
from above, abolished to a large extent the antagonistic action of blue light. With a regimen of unilateral irradiation, i.e.
when far-UV and blue light were given from the same side, a phototropic balance could be achieved with approximately equal
fluence rates of blue and UV light. Above or below this critical balance point the bending was either negative or positive.
In this setup the effect of tonic red light was complex. First, it caused an enhancement of the positive or negative bending,
and second, it caused at some fluence rates a sign reversal from positive to negative phototropism. The balance point itself
was only marginally affected. The data cannot be explained on the basis of a single photoreceptor and support the previous
notion of separate far-UV and blue-light receptors. The antagonism between these two receptors probably occurs on the level
of a red-light-absorbing receptor intermediate.
Received: 16 November 1997 / Accepted: 18 December 1997 相似文献