| Budget Amount *help |
¥17,000,000 (Direct Cost: ¥15,800,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2007: ¥5,200,000 (Direct Cost: ¥4,000,000、Indirect Cost: ¥1,200,000)
Fiscal Year 2006: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2005: ¥6,300,000 (Direct Cost: ¥6,300,000)
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| Research Abstract |
In the present project, we aimed to investigate the role of plant latex in plant defense and plant-insect interactions using mulberry trees (Morus spp) as model system.
We frond that mulberry leaves are highly toxic to caterpillars other than B mor (such as the Eri silkworm, Sarnia rkini (Saturniidae), and the cabbage moth, Mamestra brassicae (Noctuidae)), due to the ingredients of the latex. The toxicity of mulberry leaves was lost when latex was washed oft and latex-added artificial diets showed toxicity. Mulberry (M. australis) latex contained very high concentrations of alkaloidal sugarmimic glycosidase inhibitors reported to have anti-diabetic activities, such as 1, 4-dideoxy-1, 4-imino-D-arabinitol (D-AB1), and 1-deoxy nojirimycin (DNJ). Their concentrations, altogether in latex reached 1.5-2.5% (8-18% to dry weight) in several mulberry varieties. The sugarmimic alkaloids account for approximately half of the defense activity of mulberry latex against lepidopteran larvae. The remaining half comes from novel defiance protein that we found recently in mulberry latex. The defense protein showed growth-inhibitory effects to lepidopteran insects in low concentrations (0.01% wet weight).
Interestingly, the growth of the silkworm, B. mori, a mulberry specialist, is not at all affected by the presence of latex in mulberry leaves. The sugar-mimicking alkaloids toxic to lepidopteran larvae were not at all toxic to the silkworm, B mad While sucrase from S. ricird (generalist) was inhibited efficiently by sugar-mimic alkaloids, sucrase from B. mori (mulberry-specialist) was not at all inhibited even by very high concentrations of sugarmimic alkaloids, which suggests that B mon has adapted to latex-borne defense (sugarmimic alkaloids) by enzymatic adaptation.
This study shows that plant latexes are treasuries of interesting chemicals and defense proteins that play key roles in plant-insect interactions, which are also applicable in both medical and agricultural fields.
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