GIBBERELLIN-REGULATED EXPRESSION OF A MYB GENE IN BARLEY ALEURONE CELLS - EVIDENCE FOR MYB TRANSACTIVATION OF A HIGH-PL ALPHA-AMYLASE GENE PROMOTER
GIBBERELLIN-REGULATED EXPRESSION OF A MYB GENE IN BARLEY ALEURONE CELLS - EVIDENCE FOR MYB TRANSACTIVATION OF A HIGH-PL ALPHA-AMYLASE GENE PROMOTER
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DOI：
10.1105/tpc.7.11.1879
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发表时间：
1995-11-01
期刊：
影响因子：
11.6
通讯作者：
JACOBSEN, JV
中科院分区：
文献类型：
--
作者：
GUBLER, F;KALLA, R;JACOBSEN, JV
对大麦高pl α -淀粉酶基因启动子的功能分析发现，在-174 ~ -108区域存在赤霉素应答复合体，其中心元件TAACAAA序列与c-Myb和v-Myb的一致结合位点非常相似。我们研究了GA调控的Myb在大麦糊粉细胞中转激活α -淀粉酶基因表达的可能性，从大麦糊粉cDNA文库中分离到编码新Myb的cDNA克隆GAmyb， RNA印迹分析显示，GA上调了GAmyb在大麦糊粉层中的表达。GAmyb的表达动力学表明，GAmyb是ga调控基因表达的早期事件，先于α -淀粉酶基因表达，环己亚胺阻断α -淀粉酶基因表达，但未能阻断GAmyb基因表达，说明GAmyb基因表达不需要蛋白合成。重组GAMyb的凝胶迁移实验表明，GAMyb在体外特异性结合TAACAAA盒子，我们在瞬时表达实验中证明，GAMyb激活了高pl -淀粉酶启动子的转录，在没有GA的情况下融合到-葡萄糖醛酸酶报告基因。我们的研究结果表明GAMyb是高pl -淀粉酶启动子转录激活所需的唯一ga调控转录因子。因此，我们假设GAMyb是导致淀粉粒细胞α -淀粉酶基因表达的ga反应途径的一部分。
Functional analysis of a barley high-pl alpha-amylase gene promoter has identified a gibberellin (GA) response complex in the region between -174 and -108, The sequence of the central element, TAACAAA, is very similar to the c-Myb and v-Myb consensus binding site. We investigated the possibility that a GA-regulated Myb transactivates alpha-amylase gene expression in barley aleurone cells, A cDNA clone, GAmyb, which encodes a novel Myb, was isolated from a barley aleurone cDNA library, RNA blot analysis revealed that GAmyb expression in isolated barley aleurone layers is up-regulated by GA. The kinetics of GAmyb expression indicates that it is an early event in GA-regulated gene expression and precedes alpha-amylase gene expression, Cycloheximide blocked alpha-amylase gene expression but failed to block GAmyb gene expression, indicating that protein synthesis is not required for GAmyb gene expression. Gel mobility shift experiments with recombinant GAMyb showed that GAMyb binds specifically to the TAACAAA box in vitro, We demonstrated in transient expression experiments that GAMyb activates transcription of a high-pl alpha-amylase promoter fused to a beta-glucuronidase reporter gene in the absence of GA. Our results indicate that the GAMyb is the sole GA-regulated transcription factor required for transcriptional activation of the high-pl alpha-amylase promoter. We therefore postulate that GAMyb is a part of the GA-response pathway leading to alpha-amylase gene expression in aleurone cells.