Borrell Antonio, Cutanda M Cruz, Lumbreras Victoria, Pujal Judit, Goday Adela, Culiáñez-Macià Francisco A, Pagès Montserrat
Department de Genètica Molecular, Centre d'Investigació i Desenvolupament, CSIC, Barcelona, Spain.
Plant Mol Biol. 2002 Sep;50(2):249-59. doi: 10.1023/a:1016084615014.
The Arabidopsis gene Atrab28 has been shown to be expressed during late embryogenesis. The pattern of expression of Atrab28 mRNA and protein during embryo development is largely restricted to provascular tissues of mature embryos, and in contrast to the maize Rab28 homologue it cannot be induced by ABA and dehydration in vegetative tissues. Here, we have studied the subcellular location of Atrab28 protein and the effect of its over-expression in transgenic Arabidopsis plants. The Atrab28 protein was mainly detected in the nucleus and nucleolus of cells from mature embryos. In frame fusion of Atrab28 to the reporter green fluorescent protein (GFP) directed the GFP to the nucleus in transgenic Arabidopsis and in transiently transformed onion cells. Analysis of chimeric constructs identified an N-terminal region of 60 amino acids containing a five amino acid motif QPKRP that was necessary for targeting GFP to the nucleus. These results indicate that Atrab28 protein is targeted to the nuclear compartments by a new nuclear localization signal (NLS). Transgenic Arabidopsis plants, with gain of Atrab28 function, showed faster germination rates under either standard or salt and osmotic stress conditions. Moreover, improved cation toxicity tolerance was also observed not only during germination but also in seedlings. These results suggest a role of Atrab28 in the ion cell balance during late embryogenesis and germination.
拟南芥基因Atrab28已被证明在胚胎发育后期表达。Atrab28 mRNA和蛋白质在胚胎发育过程中的表达模式主要局限于成熟胚胎的原维管组织，与玉米Rab28同源物不同，它在营养组织中不能被脱落酸和脱水诱导。在这里，我们研究了Atrab28蛋白的亚细胞定位及其在转基因拟南芥植物中过表达的影响。Atrab28蛋白主要在成熟胚胎细胞的细胞核和核仁中检测到。Atrab28与报告基因绿色荧光蛋白（GFP）的读框融合将GFP导向转基因拟南芥和瞬时转化的洋葱细胞的细胞核。嵌合构建体分析确定了一个包含五个氨基酸基序QPKRP的60个氨基酸的N端区域，该区域是将GFP靶向细胞核所必需的。这些结果表明，Atrab28蛋白通过一个新的核定位信号（NLS）靶向核区室。具有Atrab28功能增益的转基因拟南芥植物在标准或盐和渗透胁迫条件下显示出更快的发芽率。此外，不仅在发芽期间，而且在幼苗中也观察到对阳离子毒性的耐受性提高。这些结果表明Atrab28在胚胎发育后期和发芽过程中的离子细胞平衡中起作用。
