報告書番号

U03016

タイトル（和文）

植物による環境修復(3) -－ﾍﾋﾞﾉﾈｺﾞｻﾞの組織培養法の確立と培養植物体のｶﾄﾞﾐｳﾑ耐性・蓄積能力について－-

タイトル（英文）

Callus culture of a metal hyper-accumulator fern, Athyrium yokoscense, and evaluation of the cadmium tolerance and accumulation capacity

概要 （図表や脚注は「報告書全文」に掲載しております）

我が国の代表的なCdﾊｲﾊﾟｰｱｷｭｰﾑﾚｰﾀｰで、栽培・増殖が困難なｼﾀﾞ植物「ﾍﾋﾞﾉﾈｺﾞｻﾞ」のCd蓄積・耐性機構を明らかにするために、組織培養法と、得られた組織のCd耐性・蓄積能力に関する検討を行った。その結果、1.ﾍﾋﾞﾉﾈｺﾞｻﾞの羽葉からｶﾙｽを形成し、増殖・再生する方法を確立した。また、2.ﾍﾋﾞﾉﾈｺﾞｻﾞはｶﾙｽにおいても、少なくとも1mMのCdに耐性を示すと共に、茎葉部に最大で約1.8mg/g-DWのCdを蓄積した。このとき、3.他の植物ではCd暴露により濃度が低下する種々の元素(Ca,Cu,Mg,Mn,Zn)には変化が見られず、Feではむしろ濃度が増加した。このことから、ﾍﾋﾞﾉﾈｺﾞｻﾞが細胞ﾚﾍﾞﾙでの本質的なCd耐性・蓄積機構を有する一方、植物体として高濃度のCd暴露時にも各金属がCdに邪魔されずに十分に吸収されるような機構を備えていると考えられる。

概要 （英文）

Calli of a metal hyper-accumulator fern, Athyrium yokoscense, were induced from the prothallium, which generated from the spore being in the sporangium on a piece of frond. These calli showed vigorous and endless growth by a periodical change of the culture medium even in a liquid culture system. When the calli were transferred onto the medium without hormones, mature plantlets were regenerated via the prothallium-like organs or embryogenic calli. Then, the Cd tolerance and accumulation capacity of these calli and regenerated plantlets were determined in the relation of six essential-metal concentrations (Ca, Cu, Fe, Mg, Mn and Zn) in tissues. Every developmental stage of the fern could grow without any damage on at least 1 mM of Cd containing medium, and accumulate up to 1.8 mg/g-DW of Cd in the frond. At this time, the tissue concentrations of these metals in calli were almost constant irrespective of the Cd exposure. Also, in the leaves of regenerated plantlets, the tissue concentration of Ca, Cu, Mg, Mn and Zn were almost constant, and that of Fe was significantly increased. Interestingly, such observations in Fe concentration in the regenerated plantlets were completely opposed in Cd-sensitive tobacco leaves. That is, in tobacco leaves, Fe and Cu concentrations were significantly decreased correspondent to the Cd exposure. In addition to the fact that the fern maintain the basic mechanism(s) for the Cd tolerance and accumulation ability even in the cell level, a specificity of the Fe-transport system within the plant body may relate to the Cd-tolerance at the intact plant level of the fern.

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