Water-soluble glucans (WSG) from a virulent isolate of Phytophthora capsici (PCAP-3) which were released during germination of cystospore markedly suppressed the elicitor-induced death of ...suspension-cultured cells of susceptible sweet pepper and tomato but not that of resistant pepper and tobacco. PCAP-3, its polygalacturonase (PGase)-deficient mutant (PCAP3-M16), and galacturonic acid non-utilizable mutant carrying the PGase (PCAP-1) activity could penetrate in epidermal cells of host leaves but similarly caused a hypersensitive response (HR) on non-injured leaves of resistant host (sweet pepper). In the case of inoculation on press-injured leaves, however, both of the resistant and nonhost plant leaves became quite susceptible to PCAP-3 similar to susceptible hosts, but not to PCAP3-M16 and PCAP-1. These results suggested that host-selectivity of Phytophthora capsici may be determined in the leaf epidermal cells where the suppressor glucans released during infection effectively suppressed the occurrence of hypersensitive reaction. Furthermore, during growth of the fungus in intercellular spaces of leaf tissues, PGase may contribute not only to the virulence expression but also the supply of initial nutrition for fungal growth in the intercellular space of host tissues
Cytoplasmic aggregation, the rapid translocation of cytoplasm and organelles to the site of fungal penetration of a cell, occurs in potato tissue after penetration of an incompatible race of
...Phytophthora infestans, the late blight fungus, or treatment with hyphal wall components (HWC) prepared from
P. infestans. This phenomenon is thought to be one of the defense reactions of plant against pathogens, but the exact function of cytoplasmic aggregation is currently unknown. To evaluate the relationship between cytoplasmic aggregation and defense reactions, we suppressed the cytoplasmic aggregation by treatment with cytochalasin D, an inhibitor of the polymerization of actin, and examined the effect of inhibition on certain defense responses caused by HWC treatment. In potato tuber discs treated simultaneously with HWC and cytochalasin D, a delay in the induction of phenylalanine ammonia-lyase mRNA, decrease in the accumulation of PR (pathogenesis-related) proteins and partial suppression of cell death were observed, while the generation of superoxide anions was not affected. These results suggested that cytoplasmic aggregation was essential for the timely induction of defense reactions manifested at late resistant stage.
Gel was prepared from shark myofibrillar proteins by reducing the pH of washed, collagen-free, shark meat homogenate in water to 4.0 by acetic acid. The gel was homogenized in water at a protein ...concentration of 3% (w/v) to get low viscous (free-flowing) dispersion. Proteins in the dispersion were stable to heating at 100°C. However, the proteins were precipitated when the dispersion was heated after either increase of pH to 6.0 or addition of salts. Spray drying of die dispersion gave colorless and odorless protein powder. Some characteristics of the powder are discussed.
A process to prepare dehydrated laminates of ribbon fish is reported. Pieces of eviscerated and beheaded fish were pressed under a screw press and the laminates obtained were subjected to air drying ...at 55°C for 14 hr. The product was golden brown in color, and had 18.4% moisture, 22% rehydration capacity, and pepsin and trypsin digestibilities of 51 and 62%, respectively. Oxidation of lipids during aerobic storage of the product at ambient temperature could be controlled by vacuum packaging. Sensory evaluation of the productfried in vegetable oil after Serobic storing at ambient temperature for 100 days suggested its acceptability. The process has potential for value addition of ribbon fish.
During the hypersensitive reaction of potato tuber discs following inoculation with an incompatible race of
Phytophthora infestans or treatment with the fungal wall elicitor (HWC-elicitor), a ...chemiluminescence (CL) was autophotographically detected on the tissues-surface by exposing X-ray film for several minutes to the fungal-inoculated or HWC-elicitor treated surface of tuber discs together with luminol. A densitometric analysis of CL on the autophotograms made it possible to show that the CL was dependent on concentrations of applied HWC-elicitor or luminol and that the presence of catalase or a scavenger of active oxygen, tiron, effectively diminished the CL. The HWC-elicitor stimulated CL was inhibited by an extracellular Ca
2+ chelator (EGTA), Ca
2+ channel blockers (verapamil, diltiazem and CoCl
2), a calmodulin inhibitor (W-7) and a protein kinase inhibitor (staurosporine). These results confirmed that a system of active oxygen generation in potato tuber discs was stimulated by infection with incompatible fungus or treatment with HWC-elicitor, and also suggested that Ca
2+, calumodulin and protein kinase may be involved in the stimulation process of the active oxygen generating system.
