Cyto toxic effect of 2 hydroxy juglone a metabolite in the branched pathway of melanin biosynthesis in pyricularia oryzae

Yamaguchi, I.; Sekido, S.; Seto, H.; Misato, T.

Journal of Pesticide Science 8(4): 545-550


ISSN/ISBN: 1348-589X
Accession: 005083162

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Scytalone and 2-hydroxyjuglone (2-HJ) are metabolites which greatly accumulate in the culture of P. oryzae due to the blocking of allo-melanin biosynthesis by such chemicals as tricyclazole or CGA 49104 (pyroquilon). Scytalone was found to be less effective than 2-HJ in reducing the viability of P. oryzae. The effects of 2-HJ on the fungal respiration system and macromolecular syntheses were investigated by using the spheroplasts of P. oryzae. Incorporation of 14C-precursors into acid-precipitable material as well as respiration was inhibited by the compound non-specifically. No such inhibitory effects were observed with CGA 49104. While inhibition by 2-HJ was particularly significant in RNA, protein and lipid syntheses, uptake of 14C-uridine or 14C-phenylalanine by spheroplasts was also inhibited by 2-HJ quite markedly, as was seen in the uptake of 14C-glucose. These results suggest that 2-HJ acts on essential biochemical processes and on membrane systems in P.oryzae. Since the fungal appressoria accumulate significant amount of 2-HJ during their maturation in the presence of tricyclazole or pyroquilon, such a metabolite may possibly play a part in the deterioration of the blast fungus pathogenicity.