Schneidereit Alexander, Scholz-Starke Joachim, Büttner Michael
Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany.
Plant Physiol. 2003 Sep;133(1):182-90. doi: 10.1104/pp.103.026674.
A genomic clone and the corresponding cDNA of a new Arabidopsis monosaccharide transporter AtSTP9 were isolated. Transport analysis of the expressed protein in yeast showed that AtSTP9 is an energy-dependent, uncoupler-sensitive, high-affinity monosaccharide transporter with a K(m) for glucose in the micromolar range. In contrast to all previously characterized monosaccharide transporters, AtSTP9 shows an unusual specificity for glucose. Reverse transcriptase-polymerase chain reaction analyses revealed that AtSTP9 is exclusively expressed in flowers, and a more detailed approach using AtSTP9 promoter/reporter plants clearly showed that AtSTP9 expression is restricted to the male gametophyte. AtSTP9 expression is not found in other floral organs or vegetative tissues. Further localization on the cellular level using a specific antibody revealed that in contrast to the early accumulation of AtSTP9 transcripts in young pollen, the AtSTP9 protein is only found weakly in mature pollen but is most prominent in germinating pollen tubes. This preloading of pollen with mRNAs has been described for genes that are essential for pollen germination and/or pollen tube growth. The pollen-specific expression found for AtSTP9 is also observed for other sugar transporters and indicates that pollen development and germination require a highly regulated supply of sugars.
分离出了一种新的拟南芥单糖转运蛋白AtSTP9的基因组克隆体及相应的cDNA。对酵母中表达的该蛋白进行转运分析表明，AtSTP9是一种能量依赖型、对解偶联剂敏感的高亲和力单糖转运蛋白，其对葡萄糖的K(m)值在微摩尔范围内。与所有先前鉴定的单糖转运蛋白不同，AtSTP9对葡萄糖表现出不同寻常的特异性。逆转录聚合酶链反应分析显示，AtSTP9仅在花中表达，使用AtSTP9启动子/报告植物的更详细方法清楚地表明，AtSTP9的表达仅限于雄配子体。在其他花器官或营养组织中未发现AtSTP9的表达。使用特异性抗体在细胞水平上进一步定位发现，与AtSTP9转录本在幼嫩花粉中的早期积累不同，AtSTP9蛋白在成熟花粉中仅微弱存在，但在萌发的花粉管中最为显著。这种花粉中mRNA的预加载现象已在对花粉萌发和/或花粉管生长至关重要的基因中有所描述。AtSTP9的花粉特异性表达在其他糖转运蛋白中也有观察到，这表明花粉发育和萌发需要高度调控的糖供应。
