Wang Y, Duby G, Purnelle B, Boutry M
Unité de Biochimie Physiologique, Université Catholique de Louvain, Croix du Sud, 2-20, B-1348 Louvain-la-Neuve, Belgium.
Plant Cell. 2000 Nov;12(11):2129-42. doi: 10.1105/tpc.12.11.2129.
The recessive nuclear vdl (for variegated and distorted leaf) mutant of tobacco was obtained by T-DNA insertion and characterized by variegated leaves and abnormal roots and flowers. Affected leaf tissues were white and distorted, lacked palisadic cells, and contained undifferentiated plastids. The variegation was due to phenotypic, rather than genetic, instability. Genomic and cDNA clones were obtained for both the mutant and wild-type VDL alleles. Three transcripts, resulting from alternate intron splicing or polyadenylation, were found for the wild type. The transcripts potentially encode a set of proteins (53, 19, and 15 kD) sharing the same N-terminal region that contains a chloroplast transit peptide capable of importing the green fluorescent protein into chloroplasts. The predicted 53-kD product belongs to the DEAD box RNA helicase family. In the homozygous vdl mutant, T-DNA insertion resulted in accumulation of the shortest transcript and the absence of the RNA helicase-encoding transcript. Genetic transformation of the homozygous mutant by the 53-kD product-encoding cDNA fully restored the wild-type phenotype. These data suggest that a plastid RNA helicase controls early plastid differentiation and plant morphogenesis.
烟草隐性核基因vdl（叶色斑驳且扭曲）突变体通过T-DNA插入获得，其特征为叶片斑驳、根和花异常。受影响的叶片组织呈白色且扭曲，缺乏栅栏细胞，含有未分化的质体。这种斑驳现象是由于表型不稳定而非遗传不稳定导致的。已获得突变体和野生型VDL等位基因的基因组和cDNA克隆。在野生型中发现了三种由可变内含子剪接或多聚腺苷酸化产生的转录本。这些转录本可能编码一组蛋白质（53、19和15 kD），它们共享相同的N端区域，该区域包含一个能够将绿色荧光蛋白导入叶绿体的叶绿体转运肽。预测的53-kD产物属于DEAD盒RNA解旋酶家族。在纯合vdl突变体中，T-DNA插入导致最短转录本的积累以及编码RNA解旋酶的转录本缺失。用编码53-kD产物的cDNA对纯合突变体进行遗传转化完全恢复了野生型表型。这些数据表明，一种质体RNA解旋酶控制着早期质体分化和植物形态发生。
