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The tissue distributions of dhurrin lphydroxy-(S)-mandelonitrhie8-Dplucosidel and ofenzymes involved in its metaboUsm have been investigated in leaf blades of light-grown Sorghu bicolor seedlngs. Enzymk digestion of these leaves using celulase has enabled preparations of epidermal and mesophyli protoplasts and bundle sheath strands to be isolated with only minor cross-contamination. Dhurrin was located entirely in the epidermal layers of the leaf blade, whereas the two enzymes responsible for its catabolism, namely dhurrin ,-glucosidase and hydroxynitrile lyase, resided almost exclusively in the mesophyli tissue. The final enzyme of dhurrin biosynthesis, uridine diphosphate glucose;p-hydroxymandelonitrile glucosyltransferase, was found in both mesophylH (32% of the total activity of the leaf blade) and epidermal (68%) tissues. The bundle sheath strands did not contain significant amounts of dhurrin or of these enzymes. It was concluded that the separation of dhurrin and its catabolic enzymes in different tissues prevents its large scale hydrolysis under normal physiological conditions. The well documented production of HCN (cyanogenesis), which occurs rapidly on crushing Sorghum leaves, would be expected to proceed when the contents of the ruptured epidermal and mesophyll cells are allowed to mix.

ABSTRACT. Clones of hepatitis B virus (HBVIndividuals infected with HBV have HBsAg, representing the viral envelope, in the circulation. In addition, they have either HBeAg, which is closely related to the viral nucleocapsid (I), or anti-HBe. The presence of HBeAg or anti-HBe in the serum is significant for the immunopathologic status of hosts and also for the biology of HBV infecting them (2).Perinatal HBV infection, resulting in a persistent camer state of babies, is transmitted by camer mothers who are positive for HBeAg (3, 4). Most babies born to them harbor HBV without symptoms; some develop a spectrum of hepatic disease ranging from chronic hepatitis to hepatocellular carcinoma later in their lives.

Race 3, a new race of Fusarium oxysporum f. sp. lactucae determined by a differential system with commercial cultivars Abstract Pathogenic variation among 26 Japanese isolates of Fusarium oxysporum f. sp. lactucae (FOL) was tested using 21 lettuce cultivars to select commercial lettuce cultivars as race differential indicators. Cultivar Costa Rica No. 4 was resistant to race 1 but susceptible to race 2, consistent with the conventional standard differential line VP1010. Cultivar Banchu Red Fire was susceptible to race 1 but resistant to race 2, which showed an opposite type of reaction as another differential line VP1013. Cultivar Patriot was susceptible to both races. The resistance reactions of the three cultivars under field conditions were identical with that observed in the seedlings. Thus cv. Costa Rica No. 4 and cv. Banchu Red Fire can be used as differential hosts to identify pathogenic races of FOL. This differential system showed that all FOL isolates obtained from diseased butterhead lettuce in Fukuoka, Japan were new races (i.e., pathogenic to three cultivars). We propose that the new race be designated race 3. Isolates of FOL, the pathogen of Fusarium wilt in lettuce, obtained from California showed the same reaction as that of race 1. Furthermore, the Japanese isolate SB1-1 (race 1) and California isolate HL-2 belonged to the same vegetative compatibility group. Our results suggest that both of the fungi are the same forma specialis.

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A new p-coumaric acid (4-hydroxycinnamic acid) hydroxylase was detected in mung bean seedlings treated with tentoxin, a fungal toxin, in which polyphenol oxidase that hydroxylates a wide variety of monophenols in vitro was completely eliminated. The enzyme required molecular oxygen and showed a pH optimum of 5.0. The enzyme acted only on p-coumaric acid (Km, 3.0 X 10(-5) M), while its specificity for the electron donor was rather broad. The Km value for NADPH (1.5 X 10(-4) M) was much lower than that for L-ascorbic acid (1.0 X 10(-2) M), although the Vmax value was almost the same with both electron donors. The enzyme was potently inhibited by beta-mercaptoethanol (Ki, 3.5 X 10(-6) M) and diethyldithiocarbamate (Ki, 2.3 X 10(-4) M), but was insensitive to p-chloromercuribenzoate. The enzyme was localized in the cell organelles which sedimented between mitochondria and endplasmic reticulum on sucrose density gradient centrifugation. The enzyme activity in the seedling was changed in response to induction by light in a manner suggesting its involvement in biosynthesis of phenolic compounds in mung bean seedlings.