報告書番号

U02041

タイトル（和文）

新規フェリチン遺伝子を用いた形質転換植物における鉄貯蔵能

タイトル（英文）

Improvement of iron storage capacity in transgenic tobacco by transferring the novel soybean ferritin gene

概要 （図表や脚注は「報告書全文」に掲載しております）

近年、植物において複数種のフェリチン遺伝子が存在し、遺伝子ファミリーを形成していることが示されている。筆者らはダイズ種子に存在するフェリチンが2種類の異なる構成タンパク質(H-1,H-2)からなることを見出した(RU01005)。本報告では、H-1或いはH-2単独での安定性、および2種類のフェリチン遺伝子をタバコに導入した場合の植物中における両フェリチンの機能を解析した。その結果、H-1フェリチンは分解されやすく、単独では構造を維持できないのに対し、H-2フェリチンは分解を受けず安定であった。各フェリチン遺伝子をタバコに導入した場合、培養日数の経過に伴ってH-2フェリチンのほうがH-1フェリチンよりも植物体内に多く蓄積する傾向を示した。また、鉄過剰条件で植物体を生育させた場合、H-2フェリチン導入植物が生長量、鉄貯蔵能ともにH-1導入植物よりも優れていた。

概要 （英文）

Ferritin is a multimeric iron storage protein, which is distributed in nearly all living kingdoms, such as plants, animals and bacteria. Ferritin has 24 subunits that are assembled into a spherical shape with inner cavity, in which up to 4500 atoms of irons can be stored as non-toxic and biologically available form. We have succeeded in producing the crops with high iron content by transferring the soybean ferritin gene. Recentry, multiple genes of ferritin have been identified in maize, cowpea and Arabidopsis. However, only one peptide chain type has been identified as a functional subunit of plant ferritin. In previous report, we have identified two ferritin subunits, H-1 and H-2, in soybean dry seed. We also suggested that the molecular weight of the H-1 subunit is 28 kDa, however, this subunit can be degraded easily to 26.5 kDa form by processing of the carboxyl terminal region. In this study, we assayed the function of soybean H-1 and H-2 ferritin in vitro and in vivo by producing the transgenic tobacco plants expressing the H-1 ferritin and H-2 ferritin. The experiments performed in vitro using the recombinant H-1 and H-2 ferritin suggested that the H-2 ferritin has been stable in the tobacco leaf extract, whereas the H-1 ferritin has been degraded completely in the same condition in 120 minutes. Next, we measured the weight and iron content of transgenic tobacco which expressed the H-1 or the H-2 ferritin. In normal condition, the iron content of both H-1 and H-2 transformants have been increased compared to the control, however, the H-1 and H-2 transformants contained nearly equal amounts of iron. On the other hand, grown in the medium containing the excess iron, the H-2 ferritin transformant has contained more iron compared to the H-1 transformant and control plant. Moreover, the control plant and H-1 transformants have shown the symptom of iron excess, whereas the H-2 transformants have not shown in such symptoms and grown normally. These data suggested that the H-2 ferritin makes iron storage ability stable and contributed to the resistance against oxidative stress generated by the excess iron.

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