Wheat germ agglutinin (WGA) levels in roots of 2-day-old wheat seedlings increased up to three-fold when stressed by air-drying. Similar results were obtained when seedling roots were incubated either in 0.5 molar mannitol or 180 grams per liter polyethylene glycol 6000, with a peak level of WGA after 5 hours of stress. Longer periods of osmotic treatment resulted in a gradual decline of WGA in the roots. Since excised wheat roots incorporate more[35S]cysteine into WGA under stress conditions, the observed increase of lectin levels is due to de novo synthesis. Measurement of abscisic acid (ABA) levels in roots of control and stressed seedlings indicated a 10-fold increase upon air-drying. Similarly, a five-and seven-fold increase of ABA content of seedling roots was found after 2 hours of osmotic stress by polyethylene glycol 6000 and mannitol, respectively. Finally, the stress-induced increase of WGA in wheat roots could be inhibited by growing seedlings in the presence of fluridone, an inhibitor of ABA synthesis. These results indicate that roots of water-stressed wheat seedlings (a) contain more WGA as a result of an increased de novo synthesis of this lectin, and (b) exhibit higher ABA levels. The stress-induced increase of lectin accumulation seems to be under control of ABA.have been many investigations on stress-induced ABA accumulation in leaves, few studies have examined endogenous ABA levels in plant roots. This paper reports enhanced ABA levels in roots of water-stressed wheat seedlings. Since ABA reportedly stimulates WGA synthesis in wheat roots (16), we further describe (a) the increase ofWGA content and synthesis in wheat seedling roots as a result of drought and osmotic stress, and (b) the inhibition of this stress-induced increase by fluridone, an inhibitor of ABA synthesis (2,4,5,14). MATERIALS AND METHODS Growth of Wheat SeedlingsWheat grains (Triticum aestivum L., cv Fidel) were surfacesterilized by consecutive treatments of 70% ethanol (3 min), sterile distilled water, 1% NaOCl (diluted commercial bleach, 30 min) and further washed in five changes of sterile distilled water. The grains were germinated under sterile conditions on moist filter paper in petri dishes (20 cm diameter), and incubated in the dark at 25C. Seedlings used for experiments were 2 d old and had three roots.

The lectin in Rhizoctonia solani is a major protein, although its function was previously unknown. An enzymelinked immunosorbent assay was developed to quantify the lectin content in mycelium, sclerotia and culture filtrate during the development of R. solmi grown in a synthetic medium. Lectin content was low in young mycelium but increased dramatically at the onset of sclerotium formation, reaching a maximum in adult sclerotia. Upon myceliogenic germination, the lectin content of the sclerotia rapidly decreased. It thus appears that the lectin is a developmentally regulated sclerotium-specific protein accumulating during sclerotium formation and disappearing during germination. Its relative abundance and the pattern of developmental control suggests that the lectin is probably a storage protein. Lectin accumulation was also influenced by the composition of the medium. Addition of supplementary carbohydrate (D-glucose) caused a marked reduction in lectin content whereas increased nitrogen in the form of L-asparagine led to a higher lectin content. However, when the L-asparagine concentration was too high, autolysis occurred and part of the lectin was released into the medium.

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Summary. The ability of 25 lectins, isolated from different plants and fungi, to agglutinate 95 clinical isolates of P-haemolytic streptococci was examined. Cell suspensions were untreated, trypsin-treated or boiled at pH 2.0. None of the 95 untreated cell suspensions gave a visible reaction with any of the lectins. When the cells were trypsinised, 42 strains were agglutinated with one or more lectin and after boiling at pH 2, all the strains were agglutinated. After treatment with trypsin, 20 different agglutination patterns were observed, and after boiling, 19 patterns, four of which were similar. A correlation was found between Lancefield group C and some of these patterns. Some lectins reacted specifically with group C streptococci ; DBA and WFA, both specific for D-GalNAc, DSA, a GlcNAc-specific lectin, and RPA, which showed a complex specificity, reacted only with group C strains. Furthermore, the lectin of Maackia amurensis reacted with 50 % of group B streptococci only. Agglutination assays with lectins were reproducible, easy to perform, relatively inexpensive and, therefore, applicable to studies of cell-wall structure and epidemiology of P-haemolytic streptococci.

Clinical isolates of Moraxella catarrhalis (n = 86) were evaluated for their haemagglutinating activity with different types of erythrocytes. Of all the isolates tested, 12 did not agglutinate with any of the erythrocytes, whereas 65 reacted with human erythrocytes of type A, B, and 0, and 26 with erythrocytes from rabbit, guinea pig, dog, or rat. None of the isolates agglutinated with sheep and goat erythrocytes. The agglutination titres ranged from 0 to 64. Among these isolates, 13 different agglutination patterns could be distinguished. The agglutinating activity was Ca(2+)-dependent and was inhibited by proteases, by temperatures exceeding 50 degrees C and by the addition of D-glucosamine or D-galactosamine. The adherence capacity of the M. catarrhalis isolates to tracheal epithelium correlated with their agglutination titre and could be inhibited by the same treatments. These data provide strong evidence that adherence of M. catarrhalis is mediated by lectins located on the bacterial surface.