A gene (NhKIN1) encoding a kinesin was cloned from Nectria haematococca genomic DNA by polymerase chain reaction amplification, using primers corresponding to conserved regions of known kinesin-encoding genes. Sequence analysis showed that NhKIN1 belongs to the subfamily of conventional kinesins and is distinct from any of the currently designated kinesin-related protein subfamilies. Deletion of NhKIN1 by transformationmediated homologous recombination caused several dramatic phenotypes: a 50% reduction in colony growth rate, helical or wavy hyphae with reduced diameter, and subcellular abnormalities including withdrawal of mitochondria from the growing hyphal apex and reduction in the size of the Spitzenkö rper, an apical aggregate of secretory vesicles. The effects on mitochondria and Spitzenkö rper were not due to altered microtubule distribution, as microtubules were abundant throughout the length of hyphal tip cells of the mutant. The rate of spindle elongation during anaphase B of mitosis was reduced 11%, but the rate was not significantly different from that of wild type. This lack of a substantial mitotic phenotype is consistent with the primary role of the conventional kinesins in organelle motility rather than mitosis. Our results provide further evidence that the microtubule-based motility mechanism has a direct role in apical transport of secretory vesicles and the first evidence for its role in apical transport of mitochondria in a filamentous fungus. They also include a unique demonstration that a microtubulebased motor protein is essential for normal positioning of the Spitzenkö rper, thus providing a new insight into the cellular basis for the aberrant hyphal morphology.

Pisatin is an isoflavonoid phytoalexin synthesized by pea (Pisum sativum L.). Previous studies have identified two enzymes apparently involved in the synthesis of this phytoalexin, isoflavone reductase (IFR), which catalyzes an intermediate step in pisatin biosynthesis, and (+)6a-hydroxymaackiain 3-O-methyltransferase (HMM), an enzyme catalyzing the terminal step. To further evaluate the involvement of these enzymes in pisatin biosynthesis, sense- and antisense-oriented cDNAs of Ifr and Hmm fused to the 35s CaMV promoter, and Agrobacterium rhizogenes, were used to produce transgenic pea hairy root cultures. PDA, a gene encoding pisatin demethylating activity (pda) in the pea-pathogenic fungus Nectria haematococca, also was used in an attempt to reduce pisatin levels. Although hairy root tissue with either sense or antisense Ifr cDNA produced less pisatin, the greatest reduction occurred with sense or antisense Hmm cDNA. The reduced pisatin production in these lines was associated with reduced amounts of Hmm transcripts, HMM protein, and HMM enzyme activity. Hairy roots containing the PDA gene also produced less pisatin. To evaluate the role of pisatin in disease resistance, the virulence of N. haematococca on the transgenic roots that produced the lowest levels of pisatin was tested. Hairy roots expressing antisense Hmm were more susceptible than the control hairy roots to isolates of N. haematococca that are either virulent or nonvirulent on wild-type pea plants. This appears to be the first case of producing transgenic plant tissue with a reduced ability to produce a phytoalexin and demonstrating that such tissue is less resistant to fungal infection: these results support the hypothesis that phytoalexin production is a disease resistance mechanism.

The activity of polygalacturonase (PC) has been detected in ripe Mclntosh apples (Malus domestica Borkh. cv Mclntosh) both by enzyme activity measurement and immunoblotting using an antitomato-PC antibody preparation. PC activity increased during fruit ripening and remained steady, or decreased slightly, after 5 months of controlled atmospheric storage. l h e enzyme had a relative molecular weight of 45,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 56,000 to 61,000 when determined by gel filtration. Viscosity and reducing end group measurements with a commercial pectin preparation showed that the enzyme is endo acting. In RNA and DNA blot hybridization experiments, a full-length tomato PC cDNA hybridized with the apple RNA and DNA, showing the identity of genes encoding the activity of the enzyme in tomato and apple.Structural changes in the cell walls of climacteric fruits that lead to softening of the tissues are initiated by the action of ethylene, the fruit-ripening hormone (Abeles, 1985). The softening of the fruit tissues is the consequence of cell walldegrading enzymes , of which endo-PG (EC 3.2.1.15) was reported to cause the most prominent changes (Crookes and Grierson, 1983). Endo-PG was implicated in tissue softening because its appearance during fruit ripening corresponds to the increase in fruit softening. In a number of cultivars, a correlation between PG activity and fruit softening has been observed (Crookes and Grierson, 1983). Also, application of isolated endo-PG preparations to fruit tissue discs resulted in ultrastructural changes that were similar to those occurring during the normal ripening process (Ben-Arie et al., 1979). Ripening mutants with delayed or decreased softening that were deficient in PG activity Koch and Nevins, 1990) gave further indications that the enzyme plays a major role in the softening of fruits.Results of recent experiments with transgenic tomato fruits, however, are not in agreement with the above assessment. Fruit softening was not affected significantly in tomatoes with down-regulated PG activity (Giovannoni et al., 1989; ' This work was supported in part by a grant from the Cornell showed that when the expression of the PG gene has been up-regulated using the promoter region of another ripeningassociated gene (Schuch et al., 1989), PG production and polyuronide degradation are increased without any detectable effect on fruit softening. These data suggest that although endo-PG activity increases during the ripening process of tomatoes, and the increased activity of this enzyme results in structural changes of the middle lamella, the softening of fruits is a more complex process than anticipated. The ripening process of fruits has been best investigated in tomatoes; however, other fruits such as peaches (Lee et al., 1990), papayas (Lazan et al., 1989), and pears (Pressey and Avants, 1976) also showed elevated activity of an endo-PG during ripening. From biological considerations it is expected that the basis of the biochemi...

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L-malate, a tricarboxylic acid cycle (TCA) intermediate, plays an important role in transporting NADH from cytosol to mitochondria for energy production and may be involved in the beneficial effects of improving physical stamina. In the present study, we investigated the effects of L-malate on the performance of forced swimming time and blood biochemical parameters related to fatigue - blood urea nitrogen (BUN), glucose (Glc), creatine kinase (CK),total protein (TP) and lactic acid (LA). To investigate the effects of L-malate on the malate-aspartate shuttle and energy metabolism in mice, the activities of enzymes related to the malate-aspartate shuttle were measured. L-malate was orally administered to mice continuously for 30 days using a feeding atraumatic needle. The swimming time was increased by 26.1 % and 28.5 %, respectively, in the 0.210 g/kg and 0.630 g/kg L-malate-treated group compared with the control group. There were no differences in the concentrations of Glc, BUN and TP between the L-malate-treated groups and the control groups. However, the levels of CK were significantly decreased in the L-malate-treated groups. The results predict a potential benefit of L-malate for improving physical stamina and minimizing muscle damage during swimming exercise. The activities of cytosolic and mitochondrial malate dehydrogenase were significantly elevated in the L-malate-treated group compared with the control group. These enzymatic activities may be useful indicators for evaluating changes affecting the malate-aspartate shuttle and energy metabolism in the liver of mice.