Stadler Ruth, Büttner Michael, Ache Peter, Hedrich Rainer, Ivashikina Natalya, Melzer Michael, Shearson Sarah M, Smith Steven M, Sauer Norbert
Molekulare Pflanzenphysiologie, Universität Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany.
Plant Physiol. 2003 Oct;133(2):528-37. doi: 10.1104/pp.103.024240. Epub 2003 Aug 14.
Guard cell chloroplasts are unable to perform significant photosynthetic CO2 fixation via Rubisco. Therefore, guard cells depend on carbon supply from adjacent cells even during the light period. Due to their reversible turgor changes, this import cannot be mediated by plasmodesmata. Nevertheless, guard cells of several plants were shown to use extracellular sugars or to accumulate sucrose as an osmoticum that drives water influx to increase stomatal aperture. This paper describes the first localization of a guard cell-specific Arabidopsis sugar transporter involved in carbon acquisition of these symplastically isolated cells. Expression of the AtSTP1 H+-monosacharide symporter gene in guard cells was demonstrated by in situ hybridization and by immunolocalization with an AtSTP1-specific antiserum. Additional RNase protection analyses revealed a strong increase of AtSTP1 expression in the dark and a transient, diurnally regulated increase during the photoperiod around midday. This transient increase in AtSTP1 expression correlates in time with the described guard cell-specific accumulation of sucrose. Our data suggest a function of AtSTP1 in monosaccharide import into guard cells during the night and a possible role in osmoregulation during the day.
保卫细胞叶绿体无法通过核酮糖-1,5-二磷酸羧化酶（Rubisco）进行显著的光合二氧化碳固定。因此，即使在光照期间，保卫细胞也依赖于相邻细胞的碳供应。由于其可逆的膨压变化，这种输入不能由胞间连丝介导。然而，几种植物的保卫细胞被证明会利用细胞外糖类或积累蔗糖作为驱动水分流入以增加气孔孔径的渗透剂。本文描述了一种参与这些质外体隔离细胞碳获取的拟南芥保卫细胞特异性糖转运蛋白的首次定位。通过原位杂交和使用AtSTP1特异性抗血清的免疫定位，证实了AtSTP1 H⁺-单糖同向转运蛋白基因在保卫细胞中的表达。额外的核糖核酸酶保护分析表明，AtSTP1表达在黑暗中强烈增加，并且在中午左右的光周期中出现短暂的、昼夜调节的增加。AtSTP1表达的这种短暂增加在时间上与所描述的保卫细胞特异性蔗糖积累相关。我们的数据表明AtSTP1在夜间将单糖输入保卫细胞中起作用，并且在白天可能在渗透调节中发挥作用。
