Expression of GFP-fusions in Arabidopsis companion cells reveals non-specific protein trafficking into sieve elements and identifies a novel post-phloem domain in roots
Expression of GFP-fusions in Arabidopsis companion cells reveals non-specific protein trafficking into sieve elements and identifies a novel post-phloem domain in roots
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DOI：
10.1111/j.1365-313x.2004.02298.x
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发表时间：
2005-01-01
期刊：
影响因子：
7.2
通讯作者：
Sauer, N
中科院分区：
文献类型：
--
作者：
Stadler, R;Wright, KM;Sauer, N
构建转基因拟南芥植物以在伴随细胞（CC）特异性AtSUC2启动子下表达一系列GFP融合蛋白（36 - 67 kDa）。这些植物被用来监测这些GFP融合蛋白从CC到筛元件（SE）和随后的易位内和外的韧皮部的贩运。结果表明，在装载韧皮部中连接SE和CC的胞间连丝具有较大的尺寸排阻限（SEL）（> 67 kDa）。膜锚定的GFP融合体和靶向内质网（ER）的GFP变体保留在CC内，并用作"零运输"对照。相反，游离GFP和所有可溶性GFP融合体从CC移动到SE中，随后通过韧皮部移位。在根尖中研究了这些移动的GFP融合体的韧皮部卸载和韧皮部后运输，其中韧皮部后运输仅发生于游离形式的GFP。所有其他可溶性GFP融合变体被卸载并限制在紧邻成熟原生韧皮部的狭窄细胞区。这似乎是细胞的这一区域，其具有约27 - 36 kDa的外周SEL，允许原韧皮部SE和周围细胞之间的蛋白质交换，但限制了大蛋白质进入根尖的一般通路。所提出的数据提供了额外的信息，在拟南芥韧皮部的发展有关的共质结构域的形成。
Transgenic Arabidopsis plants were constructed to express a range of GFP-fusion proteins (36-67 kDa) under the companion cell (CC)-specific AtSUC2 promoter. These plants were used to monitor the trafficking of these GFP-fusion proteins from the CCs into the sieve elements (SEs) and their subsequent translocation within and out of the phloem. The results revealed a large size exclusion limit (SEL) (>67 kDa) for the plasmodesmata connecting SEs and CCs in the loading phloem. Membrane-anchored GFP-fusions and a GFP variant targeted to the endoplasmic reticulum (ER) remained inside the CCs and were used as 'zero trafficking' controls. In contrast, free GFP and all soluble GFP-fusions, moved from the CCs into the SEs and were subsequently translocated through the phloem. Phloem unloading and post-phloem transport of these mobile GFP-fusions were studied in root tips, where post-phloem transport occurred only for the free form of GFP. All of the other soluble GFP-fusion variants were unloaded and restricted to a narrow zone of cells immediately adjacent to the mature protophloem. It appears that this domain of cells, which has a peripheral SEL of about 27-36 kDa, allows protein exchange between protophloem SEs and surrounding cells, but restricts general access of large proteins into the root tip. The presented data provide additional information on phloem development in Arabidopsis in relation to the formation of symplasmic domains.