Van Wuytswinkel O, Vansuyt G, Grignon N, Fourcroy P, Briat J F
Biochimie et Physiologie Moléculaire des Plantes, Centre National de la Recherche Scientifique (URA 2133), Institut National de la Recherche Agronomique et Ecole Nationale Supérieure d'Agronomie, Montpellier, France.
Plant J. 1999 Jan;17(1):93-7. doi: 10.1046/j.1365-313x.1999.00349.x.
Intracellular iron concentration requires tight control and is regulated both at the uptake and storage levels. Our knowledge of the role that the iron-storage protein ferritins play in plants is still very limited. Overexpression of this protein, either in the cytoplasm or the plastids of transgenic tobacco, was obtained by placing soybean ferritin cDNA cassettes under the control of the CAMV 35S promoter. The protein accumulated in 4- and 6-day-old seedlings and in leaves of 3-week-old plants but not in dry seeds or in 2-day-old seedlings, which is consistent with previous reports describing a post-transcriptional control of ferritin amounts during the germination process. Overaccumulated ferritin in leaves was correctly assembled as 24-mers. Transformants were more resistant to methylviologen toxicity, indicating that the transgenic ferritins were functional in vivo. Ferritin overaccumulation in transgenic tobacco leaves leads to an illegitimate iron sequestration. As a consequence, these transgenic plants behave as iron deficient and activate iron transport systems as revealed by an increase in root ferric reductase activity and in leaf iron content.
细胞内铁浓度需要严格控制，并且在摄取和储存水平上都受到调节。我们对铁储存蛋白铁蛋白在植物中所起作用的了解仍然非常有限。通过将大豆铁蛋白cDNA盒置于花椰菜花叶病毒35S启动子的控制下，在转基因烟草的细胞质或质体中获得了该蛋白的过表达。该蛋白在4日龄和6日龄的幼苗以及3周龄植株的叶片中积累，但在干种子或2日龄的幼苗中不积累，这与之前描述发芽过程中铁蛋白量的转录后控制的报道一致。叶片中过度积累的铁蛋白正确组装成24聚体。转化体对甲基紫精毒性更具抗性，表明转基因铁蛋白在体内具有功能。转基因烟草叶片中铁蛋白的过度积累导致非法的铁螯合。因此，这些转基因植物表现出缺铁，并激活铁转运系统，这通过根铁还原酶活性和叶片铁含量的增加得以揭示。
