Fobis-Loisy I, Loridon K, Lobréaux S, Lebrun M, Briat J F
Laboratoire de Biochimie et Physiologie Végétales, Institut National de la Recherche Agronomique et Ecole Nationale Supérieure d'Agronomie, Montpellier, France.
Eur J Biochem. 1995 Aug 1;231(3):609-19. doi: 10.1111/j.1432-1033.1995.tb20739.x.
In plants, synthesis of the iron-storage protein ferritin in response to iron is not regulated at the translational level; this is in contrast to ferritin synthesis in animals. Part of the response is mediated through a transduction pathway which involves the plant hormone abscisic acid. In this work, we report the cloning and sequencing of two maize ferritin genes (ZmFer1 and ZmFer2) coding for members of the two ferritin mRNA subclasses, FM1 and FM2, respectively. Although plant and animal ferritins are closely related proteins, a major difference is observed between the organisation of the genes. Both maize ferritin genes are organised as eight exons and seven introns, the positions of which are identical within the two genes, while animal ferritin genes are interrupted by three introns, at positions different from those found in maize genes. Sequence divergence between the 3' untranslated regions of these genes has allowed the use of specific probes to study the accumulation of FM1 and FM2 transcripts in response to various environmental cues. Such probes have shown that FM1 and FM2 transcripts accumulate with differential kinetics in response to iron; FM1 mRNA accumulate earlier than FM2 mRNA and only FM2 transcripts accumulate in response to exogenous abscisic acid or water stress. Mapping of the transcriptional initiation region of these two genes defined their 5' upstream regions and allowed a sequence comparison of their promoters, which appeared highly divergent. This raises the possibility that the differential accumulation of FM1 and FM2 mRNAs in response to iron, abscisic acid and drought could be due to differential transcription of ZmFer1 and ZmFer2.
在植物中，铁储存蛋白铁蛋白响应铁元素的合成并非在翻译水平受到调控；这与动物中铁蛋白的合成情况相反。部分响应是通过一条涉及植物激素脱落酸的转导途径介导的。在这项研究中，我们报告了两个玉米铁蛋白基因（ZmFer1和ZmFer2）的克隆与测序，这两个基因分别编码铁蛋白mRNA两个亚类FM1和FM2的成员。尽管植物和动物的铁蛋白是密切相关的蛋白质，但在基因结构上观察到一个主要差异。两个玉米铁蛋白基因均由八个外显子和七个内含子组成，它们在这两个基因中的位置相同，而动物铁蛋白基因被三个内含子打断，其位置与玉米基因中的不同。这些基因3'非翻译区之间的序列差异使得能够使用特异性探针来研究FM1和FM2转录本在各种环境信号响应下的积累情况。此类探针已表明，FM1和FM2转录本响应铁元素时以不同的动力学积累；FM1 mRNA比FM2 mRNA积累得更早，并且只有FM2转录本响应外源脱落酸或水分胁迫而积累。对这两个基因转录起始区域的定位确定了它们的5'上游区域，并允许对其启动子进行序列比较，结果显示它们高度不同。这增加了一种可能性，即FM1和FM2 mRNA响应铁、脱落酸和干旱时的差异积累可能是由于ZmFer1和ZmFer2的差异转录所致。
