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61.
We found that the gradient of a host-specific attractant, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) isolated from the roots of spinach triggered encystment followed by germination of zoospores of Aphanomyces cochlioidesat a concentration less than micromolar order. This compound did not affect the growth and reproduction of this phytopathogen up to 10–6 M concentration in the culture medium. We also observed that mastoparan, an activator of heterotrimeric G-protein could inhibit the motility of zoospores and then strikingly effect encystment followed by 60–80% germination of cysts. Concomitant application of cochliophilin A and mastoparan showed stronger encystment followed by 100% germination of cysts. In addition, we have observed that chemicals interfering with phospholipase C activity (neomycin) and Ca2+ influx/release (EGTA and loperamide) suppress cochliophilin A or mastoparan induced encystment and germination. These results suggest that G-protein mediated signal transduction mechanism may be involved in the differentiation of the A. cochlioides zoospores. This is the first report on the differentiation of oomycete zoospores initiated by a host-specific plant signal or a G-protein activator. 相似文献
62.
We here demonstrate the presence of a plasma membrane-associated phospholipase A2 (EC 3.1.1.4; PLA2) activity in spinach (Spinacia oleracea) leaves. The pH profile of the spinach plasma membrane PLA2 activity revealed two peaks, one at pH 4.4 and one at pH 5.5. The activity at pH 5.5 had an absolute requirement of Ca2+, with full enzyme activity at 10 μmol/L Ca2+. The Ca2+-dependent PLA2 activity was both heat sensitive and stimulated by diacylglycerol, whereas ATP completely inhibited the activity. Thus, the spinach plasma membrane contains a Ca2+-dependent PLA2 activity, which has not previously been characterised in plants. Cold acclimation of spinach resulted in a 2.2-fold higher plasma membrane PLA2 activity whereas the plasma membrane phospholipase D activity remained unaffected. Taken together, our data suggest a role of PLA2 in cold acclimation in plants. 相似文献
63.
64.
Helen J. Mosson Elaine H. Richards Gay C. Marris John P. Edwards 《Physiological Entomology》2000,25(3):296-302
Serum from larvae of Lacanobia oleracea L. (Lepidoptera; Noctuidae) parasitized by Eulophus pennicornis (Hymenoptera; Eulophidae) and from normal non‐parasitized larvae is capable of agglutinating rabbit, sheep, calf, goat, chicken, horse and human erythrocytes, but not yeast. Studies with a range of inhibitory carbohydrates showed that serum lectins(s) had specificity for sugars containing galactose and for rhamnose, and for the glycosubstances fetuin and asialofetuin. Lectin activity is heat‐labile and is not dependent on calcium. Parasitism by E. pennicornis caused an increase in the agglutination titre of the serum from larvae of L. oleracea but not an increase in specific activity (titre per mg protein per ml). However, when venom from the venom gland of female wasps was injected into L. oleracea larvae, both the agglutinating activity and the specific activity of the larval serum increased. The possible causes of this increase are discussed. It is suggested that venom contains antigenic components which, when injected into the haemocoel of the L. oleracea larva, may be increasing lectin synthesis and/or release into the serum. 相似文献
65.
J. Dupont 《Physiologia plantarum》1981,52(2):225-232
Incubation of cauliflower bud mitochondria in the presence of 5 mM CaCl2 results in a rapid hydrolysis of the main membrane phospholipsds. Under the action of phospholipase D, phosphatidic acid is produced and forms, within the membranes, a very labile complex with Ca2+ and HPO42-ions present in the incubation medium. With time, one observes a first step characterized by the formation of phosphatidic acid, followed by a second step linked to the breakdown of this phospholipid. The enzyme responsible for the disappearance of phosphalidic acid has been identified as lipoxygenase. In the presence of molecular oxygen, this enzyme acts on the polyun-saturated fatty acids of phosphatidic add (mainly C18:2 and C18:3) yielding small water-soluble molecules, one of them being identified as malondialdehyde (1, 3-propanedial). Experiments involving inhibitory conditions of the breakdown of phosphatidic acid indicate that lipoxygenase acts directly on membrane-bound phosphatidic acid without previous, involvement of a lipolytic acyl hydrolase activity. In addition, the lipoxygenase activity is fully sensitive to hydroxamate derivatives. It is proposed that the lipoxygenase activity may account for a part of the mitochondrial alternative electron pathway that is insensitive to cyanide. 相似文献
66.
67.
Different regulation of leaf respiration between Spinacia oleracea, a sun species, and Alocasia odora, a shade species 总被引:1,自引:0,他引:1
Mature leaves of shade species exhibit lower respiratory rates than those of sun species. To elucidate the mechanism underlying different respiratory rates between sun and shade species, we examined respiratory properties of leaves in Spinacia oleracea L., a sun species, and Alocasia odora (Lodd.) Spach, a shade species, with special reference to changes in the respiratory rate throughout the night. In S. oleracea , rates of both CO2 efflux and O2 uptake decreased with time during the night, whereas in A. odora both rates were virtually constant at lower levels. The rates of O2 uptake in S . oleracea increased upon addition of sucrose, and the rates attained were virtually identical throughout the night. However, the addition of an uncoupler [carbonyl cyanide p -(trifluoromethoxy)-phenylhydrazone; FCCP] did not alter the rates. In contrast, the rates of O2 uptake in A. odora were enhanced by the addition of FCCP, but not by sucrose. The concentrations of carbohydrates in the tissue decreased throughout the night in both species and the ATP/ADP ratio was always greater in A. odora. These results indicate that, in S. oleracea , the availability of respiratory substrate determines the respiratory rate, while the low respiratory rate in A. odora is ascribed to its low demand for ATP. 相似文献
68.
The leaves of mistletoe (Viscum album L.) contain three galactose- and N-acetylgalactosamine-specific isolectin groups (ML I, II, III). The groups ML I and ML
III showed strong cryoprotective activity during freezing and thawing of isolated spinach (Spinacia oleracea L.) thylakoid membranes, while ML II showed no such activity. The cryoprotective efficiency of the proteins was correlated
with their relative hydrophobicity, as determined by a fluorescence titration assay. We found that the frost hardiness of
mistletoe leaves was seasonally regulated under natural conditions. While leaves harvested in winter were not damaged by freezing
to −20 °C, leaves harvested in July had already suffered 70% electrolyte leakage after freezing to −5 °C. Likewise, the amount
of ML I and ML III varied during the year, with the highest amounts of these cryoprotective lectins in winter and early spring
and the lowest amounts during the summer months. There was no comparable change in the amount of ML II. These data suggest
that some lectins may play a role in the stabilization of cellular membranes under environmental stress conditions.
Received: 18 December 1996 / Accepted: 29 March 1997 相似文献
69.
Polymorphism of the kinase domain of the S-locus receptor kinase gene (SRK) in Brassica oleracea L. 总被引:2,自引:0,他引:2
T. Nishio M. Kusaba K. Sakamoto D. J. Ockendon 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):335-342
DNA polymorphism of the S-locus receptor kinase gene (SRK) participating in self-incompatibility in Brassica was analyzed by PCR-RFLP and nucleotide sequencing. In the screening of primers for specific amplification of polymorphic
DNA fragments of SRK, the best combination was that of a forward primer (PK1) having the nucleotide sequence of the second exon of S6 SRK and a reverse primer (PK4) having the complementary nucleotide sequence of the fifth exon of S6 SRK. PCR using this primer pair amplified DNA fragments of 0.9–1.0 kb from 36 S haplotypes out of 42 tested. These DNA fragments showed high polymorphism in polyacrylamide-gel electrophoresis after digestion
with restriction endonuclease(s): 25 types were found in a double digestion with MboI and AfaI. Nucleotide sequencing of the DNA fragments amplified from five S haplotypes showed that the third, fourth, and fifth exons of SRK are highly conserved, and that there are high variations of the second and third introns of SRK, which produced polymorphism of the band pattern in PCR-RFLPs. Another forward primer (PK5) having the nucleotide sequence
of the second exon, which is derived from S2 SRK, amplified DNA fragments of almost the same region of SRK from 27 S haplotypes in combination with PK4. Although SRK alleles of the class-II S haplotypes were not amplified, all of the class-I S-haplotypes were amplified with a primer mixture of PK1, PK4 and PK5. The DNA fragments of both SRK alleles in S heterozygotes, or a 1 : 1 mixture of the genomic DNA of different S homozygotes, were amplified without exception, suggesting the usefulness of these primers for the identification of S heterozygotes. The DNA fragment sizes obtained by digestion with restriction endonucleases served as markers for the identification
of S haplotypes.
Received: 15 December 1996 / Accepted: 14 February 1997 相似文献
70.
L. J. De Kok C. Elisabeth E. Stuiver M. Rubinigg Sue Westerman D. Grill 《Plant biology (Stuttgart, Germany)》1997,110(5):411-419
Brassica oleracea L. was rather insensitive to atmospheric H2S: growth was only negatively affected at ≥0.4 μl I?1. Shoots formed a sink for H2S and the uptake rate showed saturation kinetics with respect to the atmospheric concentration. The H2S uptake rate was high in comparison with other species, which may reflect the high sulfur need of Brassica. The net uptake of sulfate by roots of hydroponically grown plants was substantially reduced after one week of exposure to 0.25 μl l?1 H2S, indicating that plants switched in part from sulfate to H2S as sulfur source for plant growth. Plants were sulfur deficient after two weeks of sulfur deprivation, illustrated by reduced growth, which was more pronounced for shoots than for roots, and in enhanced shoot dry matter content. The latter could for the greater part be attributed to enhanced levels of soluble sugars and starch. Sulfur deficiency was further characterized by a low pigment content, extremely low levels of sulfate and water-soluble non-protein thiols, and by enhanced levels of nitrate and free amino acids, particularly in the shoots. Furthermore, sulfur deficient plants contained a lower total lipid content in shoots, whereas its content in roots was unaffected. The level of sulfolipids was decreased in both roots and shoots. When sulfur deprived plants were exposed to 0.25 μl I?1 H2S for one week, all sulfur deficiency symptoms were abolished and growth was restored. Furthermore, plants were able to grow with 0.4 μl I?1 H2S as the sole sulfur source. Water-soluble non-protein thiol content was enhanced in both shoots and roots of H2S exposed plants, irrespective of the sulfate supply to the roots, whereas plants grown with H2S as sole sulfur source contained very low sulfate levels. The interaction between atmospheric and pedospheric sulfur nutrition in plants is discussed. 相似文献