報告書番号

U97042

タイトル（和文）

鉄貯蔵タンパク質フェリチン遺伝子の導入によるイネ種子中の鉄含有量の向上

タイトル（英文）

Accumulation of iron in rice seed by transferring the soybean iron storage protein ferritin gene

概要 （図表や脚注は「報告書全文」に掲載しております）

フェリチンによる鉄貯蔵機能を単子葉植物であるイネの種子に持たせることを目的として遺伝子組換え体を作出した。その結果ダイズから単離したフェリチン遺伝子が単子葉植物であるイネにおいても同様に発現し、フェリチンタンパク質を合成すること、合成されたタンパク質中に大量の鉄分を貯蔵すること（最大38.1±4.5㎎/ｇ－DW）が明らかとなった。また、このフェリチンタンパク質は、改良したプロモーターの働きによりイネの種子中にのみ特異的に合成されることが示された。動物のフェリチンでは、鉄以外の重金属の蓄積に関する報告があり、今後構造遺伝子部分の改良によって、電源立地の好適環境創造のためのバイオリメディエーションに応用することが可能であると考えられる。

概要 （英文）

Ferritin is an iron storage protein that is distributed through the living kingdom, such as bacteria, animals and plants. The mammalian ferritin is well studied at both the amino acid and the nucleic acid levels and is known to be a huge molecule consisting of homologous 24 ferritin subunits. The molecular weight of the ferritin is estimated at about 450 kD, and the molecule can store up to 4,500 iron atoms. In plants, including soybean, French bean and maize, the ferritin gene has recently been isolated and sequenced. The deduced amino acid sequences are not homologous to that of the mammalians, though it shows the similar molecular conformation and iron storage capacity. In this study, we introduced the soybean ferritin gene into rice plant (Oryza sativa L. cv Kita-ake) via Agrobacterium-mediated transformation to increase the iron content. The Introduced ferritin gene was regulated by the rice seed storage protein glutelin promoter, GluB-1 (-1209/+18) and terminated by the Nos polyadenilation signal. The transformants were grown in a green house till harvesting at the flood condition. Synthesis of the soybean ferritin protein was confirmed in each of the transformed rice seeds by western blot analysis using antibody to the soybean ferritin subunit produced by the E. coli harboring the ferritin gene expression vector pQE30. Seeds from transformants were individually wet-ashed with HN03 and H202 solution. The Iron content was then measured by absorption of Fe-o-phenanthrolin at 510nm. The results indicated that the soybean ferritin protein could be similarly synthesized in heterogenic rice plant. It was notable that seeds from the transformants store up to three times more iron atoms than normal seeds. Furthermore, since the GluB-1 promoter expresses the following structural gene specifically in the rice endosperm, the excess iron atoms were accumulated in the edible part of the rice seed other than in the embryo.

報告者

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