Actin microfilaments (F-actin) are major components of the cytoskeleton essential for many cellular dynamic processes (vesicle trafficking, cytoplasmic streaming, organelle movements). The aim of this study was to examine whether cortical actin microfilaments might be implicated in the regulation of nutrient uptake in root and leaf cells of Beta vulgaris. Using antibodies raised against actin and the AtSUC1 sucrose transporter, immunochemical assays demonstrated that the expression of actin and a sucrose transporter, showed different characteristics, when detected on plasma membrane vesicles (PMVs) purified from roots and from leaves. The in situ immunolabeling of actin and AtSUC1 sites in PMVs and tissues showed their close proximity to the plasma membrane. Using co-labeling in protoplasts, actin and sucrose transporters were localized along the internal border and in the outermost part of the plasma membrane, respectively. This respective membrane co-localization was confirmed on PMVs and in tissues using transmission electronic microscopy. The possible functional role of actin in sucrose uptake (and valine uptake, comparatively) by PMVs and tissues from roots and leaves was examined using the pharmacological inhibitors, cytochalasin B (CB), cytochalasin D (CD), and phalloidin (PH). CB and CD inhibited the sucrose and valine uptake by root tissues in a concentration-dependent manner above 1 μM, whereas PH had no such effect. Comparatively, the toxins inhibited the sucrose and valine uptake in leaf discs to a lesser extent. The inhibition was not due to a hindering of the proton pumping and H+ -ATPase catalytic activity determined in PMVs incubated in presence of these toxins.

中文翻译：

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肌动蛋白对甜菜主根和叶中蔗糖和缬氨酸吸收的影响

肌动蛋白微丝（F-肌动蛋白）是许多细胞动态过程（囊泡运输、细胞质流、细胞器运动）必不可少的细胞骨架的主要成分。本研究的目的是检查皮质肌动蛋白微丝是否可能与甜菜根和叶细胞营养吸收的调节有关。使用针对肌动蛋白和 AtSUC1 蔗糖转运蛋白的抗体，免疫化学分析表明，当在从根和叶中纯化的质膜囊泡 (PMV) 上检测时，肌动蛋白和蔗糖转运蛋白的表达显示出不同的特征。PMV 和组织中肌动蛋白和 AtSUC1 位点的原位免疫标记显示它们与质膜非常接近。在原生质体中使用共标记，肌动蛋白和蔗糖转运蛋白分别位于质膜的内部边界和最外层。使用透射电子显微镜在 PMV 和组织中证实了这种各自的膜共定位。使用药理学抑制剂细胞松弛素 B (CB)、细胞松弛素 D (CD) 和鬼笔环肽 (PH) 检查了肌动蛋白在 PMV 和根和叶组织吸收蔗糖（和缬氨酸吸收）中可能的功能作用。CB 和 CD 在 1 μM 以上以浓度依赖性方式抑制根组织对蔗糖和缬氨酸的吸收，而 PH 没有这种作用。相比之下，毒素在较小程度上抑制叶盘中蔗糖和缬氨酸的吸收。