Differential distribution of proteins expressed in companion cells in the sieve element-companion cell complex of rice plants
Differential distribution of proteins expressed in companion cells in the sieve element-companion cell complex of rice plants
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DOI：
10.1093/pcp/pci190
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发表时间：
2005-11-01
影响因子：
4.9
通讯作者：
Hayashi, H
中科院分区：
文献类型：
--
作者：
Fukuda, A;Fujimaki, S;Hayashi, H
筛管由筛元组成，这些去核细胞不能合成RNA和蛋白质。筛元中的蛋白质通过胞间连丝从邻近的伴生细胞中获得。在水稻植物中，尚不清楚是否所有伴生细胞中产生的蛋白质在筛元-伴生细胞复合体中具有相同的分布模式。本研究分析了β -葡萄糖醛酸酶（GUS）、绿色荧光蛋白（GFP）、硫氧还蛋白h （TRXh）和谷胱甘肽s -转移酶（GST） 4种蛋白的分布规律。外源蛋白GUS和GFP在TRXh基因启动子（PTRXh）的调控下在水稻植株中表达。对PTRXh-GUS和PTRXh-GFP植株叶片截面的分析表明，GUS和GFP分别在伴生细胞中富集，而不是在筛元中富集。在转基因水稻叶鞘的韧皮部汁液中也检测到GUS和GFP，表明这些蛋白可以进入筛选元件。比较韧皮部汁液和叶片总提取物中GFP和内源韧皮部蛋白TRXh和GST的相对含量。与TRXh和GST相比，叶片总提取物中GFP含量较高，韧皮部汁液中GFP含量较低，说明GFP主要在伴生细胞中积累，而不是在筛元中积累。另一方面，TRXh和GST似乎在筛选元件中而不是在伴生细胞中积累。这些结果表明，蛋白质在水稻筛选元件和伴生细胞之间的分布存在差异。
Sieve tubes are comprised of sieve elements, enucleated cells that are incapable of RNA and protein synthesis. The proteins in sieve elements are supplied from the neighboring companion cells through plasmodesmata. In rice plants, it was unclear whether or not all proteins produced in companion cells had the same distribution pattern in the sieve element-companion cell complex. In this study, the distribution pattern of four proteins, beta-glucuronidase (GUS), green fluorescent protein (GFP), thioredoxin h (TRXh) and glutathione S-transferase (GST) were analyzed. The foreign proteins GUS and GFP were expressed in transgenic rice plants under the control of the TRXh gene promoter (PTRXh), a companion cell-specific promoter. Analysis of leaf cross-sections of PTRXh-GUS and PTRXh-GFP plants indicated high accumulation of GUS and GFP, respectively, in companion cells rather than in sieve elements. GUS and GFP were also detected in phloem sap collected from leaf sheaths of the transgenic rice plants, suggesting these proteins could enter sieve elements. Relative amounts of GFP and endogenous phloem proteins, TRXh and GST, in phloem sap and total leaf extracts were compared. Compared to TRXh and GST, GFP content was higher in total leaf extracts, but lower in phloem sap, suggesting that GFP accumulated mainly in companion cells rather than in sieve elements. On the other hand, TRXh and GST appeared to accumulate in sieve elements rather than in companion cells. These results indicate the evidence for differential distribution of proteins between sieve elements and companion cells in rice plants.