| Co-Investigator(Kenkyū-buntansha) |
FUKUI Yasuhisa University of Tokyo, Graduate School of Agricultural & Life Sciences, Professor, 大学院・農学生命科学研究科, 教授 (00181248)
NAKAJIMA Hiromitsu Tottori University, Department of Agriculture, Professor, 農学部, 教授 (40144646)
INANAGA Shinobu Tottori University, Arid Land Research Center, Professor, 乾燥地研究センター, 教授 (40124664)
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| Budget Amount *help |
¥11,600,000 (Direct Cost: ¥11,600,000)
Fiscal Year 2001: ¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1999: ¥5,500,000 (Direct Cost: ¥5,500,000)
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| Research Abstract |
Metabolites of the fungus Fusarium solani (Sud 96) inhibited Striga hermonthica germination induced by the germination stimulant GR24. The, active principles were identified as trichothecenes acuminatin, neosolaniol, 8-acetylneosolaniol and tetraacetoxy T-2 tetraol (neosolaniol diacetate) on the basis of their chromatographic behavior, NMR, and mass spectra. Inhibitory activity of the four trichothecenes against Striga germination increased with acetylation of hydroxyl moieties. 8-Acetylneosolaniol, the most abundant inhibitor produced by the fungus, completely inhibited Striga germination at 24 μM. The fungal toxin did not affect germination of sorghum, a host crop, but retarded root and shoot elongation of the seedlings by 60 % and 30 %, respectively, at the same concentration.
Germination stimulant produced by Menispermum dauricum root culture was purified and identified as (+)-strigol on the basis of chromatographic behavior, NMR, MS, UV, and CD spectra. The isolated amount of (+)-s
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trigol was calculated to be about 140 μg from 61 culture filtrate. This culture will make it possible to study biosynthesis of the germination stimulant.
Total RNA extracted from germinating seeds 12 h after GR24 treatment was used for PCR-based amplification of cDNA fragments encoding the ACC synthase- and oxidase-active site domains. Two distinct cDNA fragments encoding ACC synthase (SHACS1 and SHACS2) and one encoding ACC oxidase (SHACO1) were cloned and sequenced. Southern hybridization suggested that each of the cloned genes has a single copy in the genome of S.hermonthica.
Northern blot analyses showed that expression of SHACS1 exhibited a temporal change, with a peak at 10 h after GR24 treatment, which was in accord with that of ethylene evolution from the seeds. SHACS2 was expressed at a low level with a similar trend. SHACO1 exhibited a temporal change with a peak at 15 days during conditioning, where seed response to GR24 was maximum. Based on these results, it is concluded that ACC oxidase and ACC synthase are responsive to conditioning and germination stimulant, respectively. Both the enzymes act concertedly to biosynthesize ethylene, which induces seed germination. Less
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