Gao J, Kim S R, Chung Y Y, Lee J M, An G
Department of Chemical Engineering, Washington State University, Pullman 99164-6340.
Plant Mol Biol. 1994 Aug;25(5):761-70. doi: 10.1007/BF00028872.
Two cDNA clones, TSC29 and TSC40, were isolated from a cDNA library prepared from three-day-old tobacco cell suspension grown to early exponential stage. DNA sequence analyses and database searches revealed that the TSC29 transcript encodes a protein which is highly homologous to eukaryotic 60S ribosomal (r)-protein L25 and that the TSC40 product is homologous to rat 60S r-protein L34. Southern blot analysis showed that the putative r-protein genes are members of multigene families. Transcript levels of both genes were most abundant in three-day-old cell suspension and declined in older cultures. Transcripts were also present in plant vegetative and reproductive organs. However, for TSC40 in particular, the mRNA levels were lower in plant organs than in three-day-old cell suspension. Stems and roots exhibited higher expression than leaves and flowers, indicating that these clones are differentially regulated in various cell types. Both genes were expressed at low levels in mature seeds but transcript levels significantly increased after one day of germination, remained at a high level until day 4, and declined after day 5. In situ localization experiments with germinating seedlings revealed that the TSC29 transcript was preferentially localized in root tips, epidermis, and endosperm. Wounding increased the steady-state mRNA amounts of these r-protein genes, and 2,4-dichlorophenoxyacetic acid and benzyladenine further increased the transcript level.
从处于早期指数生长期的3日龄烟草细胞悬浮液制备的cDNA文库中分离出两个cDNA克隆，即TSC29和TSC40。DNA序列分析和数据库检索表明，TSC29转录本编码一种与真核生物60S核糖体（r）蛋白L25高度同源的蛋白质，TSC40产物与大鼠60S r蛋白L34同源。Southern印迹分析表明，推定的r蛋白基因是多基因家族的成员。两个基因的转录水平在3日龄细胞悬浮液中最为丰富，而在较老的培养物中下降。转录本也存在于植物的营养器官和生殖器官中。然而，特别是对于TSC40，其在植物器官中的mRNA水平低于3日龄细胞悬浮液中的水平。茎和根的表达高于叶和花，表明这些克隆在不同细胞类型中受到差异调节。两个基因在成熟种子中表达水平较低，但在萌发1天后转录水平显著增加，直到第4天保持在高水平，第5天后下降。对萌发幼苗的原位定位实验表明，TSC29转录本优先定位于根尖、表皮和胚乳。创伤增加了这些r蛋白基因的稳态mRNA量，2,4-二氯苯氧乙酸和苄基腺嘌呤进一步提高了转录水平。
