Sugar-inducible gene expression and vacuolar accumulation of storage proteins

通过酵母单杂交筛选，获得了甘薯块根糖诱导基因中含有两个序列基序的DNA片段，分离出两个功能未知的转录因子。其中一个编码一个具有HD-Zip结构域的蛋白，该蛋白与Box 3基序结合，并在其c端含有活化结构域。另一个为一类新的bZIP因子编码。拟南芥（Arabidopsis thaliana）突变体显示糖诱导的Atβ-Amy基因的表达减少和花青素的积累，通过基于图谱的克隆，鉴定了一个突变，该突变伴随glly到Glu的替换，在一个功能未知的大蛋白中。在55个糖诱导的突变体中，Spo^<min>:: LUC报告基因表达改变。我们通过图谱克隆鉴定了hsi2。HSI2是一种具有B3 DNA结合域的新蛋白，零突变和过表达分析表明，HSI2是Spo^<min>的抑制因子。通过筛选Spo^<min>:: LUC转基因植株的激活标记系，鉴定出3个低糖条件下表达LUC报告基因的克隆。在这些突变体中，编码bZIP因子、CCT基序蛋白和功能未知的AP2结构域蛋白的基因通过插入增强子而表达升高。特别是，新型bZIP的表达增强导致了除Spo^<min>::LUC外的一些内源性糖诱导基因的表达增强。利用覆盖拟南芥所有基因的寡聚微阵列技术，我们鉴定出糖以环己亚胺不敏感的方式快速诱导或抑制转录因子基因。在这些。研究发现，糖诱导的PR-1基因表达需要atbzip22，糖抑制的AtbZIP63参与糖饥饿诱导的基因表达。我们还发现糖诱导了大量参与核糖体生物发生的基因的表达，核蛋白在核糖体生物发生的调控中起着重要作用。少

By yeast one-hybrid screen with DNA fragment containing two sequence motifs conserved among the sugar-inducible genes of sweet potato tuberous roots, two tobacco cDNAs coding for putative transcription factors with unknown function were isolated. One of them codes for a protein with HD-Zip domain that binds to Box 3 motif and contains activation domain in its C-terminus. Another one codes for a novel class of bZIP factor. Map-based cloning of lbal mutant of Arabidopsis thaliana that shows reduced sugar-inducible expression of Atβ-Amy gene and accumulation of anthocyanin resulted in identification of a mutation that accompany Gly to Glu substitution in a large protein with unknown function. Among 55 mutants that show altered sugar-inducible expression of Spo^<min> : : LUC reporter. we identified hsi2 by map-based cloning. HSI2 was a novel protein with B3 DNA binding domain and analysis of null-mutant and overexpressor indicated that HSI2 is a reptessor of Spo^<min>. By screening of acti … More vation tagging lines of Spo^<min> : : LUC transgenic plant, three clones that express LUC reporter under low-sugar condition were identified. In these mutants, expression of genes encoding bZIP factor, CCT motif protein and AP2 domain protein with unknown functions were elevated by insertion of enhancer. In particular, enhanced expression of the novel bZIP resulted in enhanced expression of some of the endogenous sugar-inducible genes in addition to Spo^<min> : :LUC. By using oligo-microarray covering all genes of Arabidopsis, we identified transcription factor genes whoes expression is rapidly induced or repressed by sugars in a cycloheximide-insensitive manner. Among these. AtbZIP 22 was found to be required for the sugar-inducible expression of PR-1 gene, and the sugar-repressible AtbZIP63 was shown to be involved in the sugar starvation-induced gene expression. We also found that sugar induces expression of a large number of genes involved in ribosome biogenesis, and nucleolin plays an important role in the regulation of ribosome biogenesis. Less