In Artemisia annua plants, glandular trichomes (GTs) are responsible for the biosynthesis and secretion of sesquiterpene lactones including artemisinin/arteannuin B. Nonspecific lipid transfer proteins (LTPs) in plants bind and carry lipid molecules across the cell membrane and are also known as secretary proteins. Interestingly, the transcripts of LTP genes are exceptionally abundant in the GTs of A. annua. In the present study, we isolated two trichome-specific LTP genes (AaLTP3 and AaLTP4) from a Korean ecotype of A. annua. AaLTP3 was expressed abundantly in shoots, whereas AaLTP4 was expressed in flowers. The GUS signal driven by the AaLTP3 or AaLTP4 promoter in transgenic A. annua plants revealed that the AaLTP3 promoter was active on hair-like non-GTs and that the AaLTP4 promoter was active on GTs. Analysis of enhanced cyan fluorescent protein (ECFP) fluorescence fused with the AaLTP3 or AaLTP4 protein in transgenic tobacco revealed that ECFP florescence was very bright on secreted lipids of long GTs. Moreover, the florescence was also bright on the head cells of short trichomes and their secreted granules. Immunoblotting analysis of GT exudates in petioles of A. annua revealed a strong positive signal against the AaLTP4 antibody. Overexpression of AaLTP3 or AaLTP4 in transgenic A. annua plants resulted in enhanced production of sesquiterpene lactones (arteannuin B, artemisinin, dihydroartemisinic acid and artemisinic acid) compared with those of wild type. The present study shows that LTP genes (AaLTP3 or AaLTP4) play important roles in the sequestration and secretion of lipids in GTs of A. annua, which is useful for the enhanced production of sesquiterpene lactones by genetic engineering.

中文翻译：

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脂质转移蛋白（AaLTP3和AaLTP4）参与青蒿中腺毛滴虫的倍半萜烯内酯分泌。

在青蒿植物中，腺毛（GTs）负责倍半萜内酯（包括青蒿素/青蒿素B）的生物合成和分泌。植物中的非特异性脂质转移蛋白（LTP）结合并在细胞膜上携带脂质分子，也被称为秘书蛋白质。有趣的是，在青蒿的GT中，LTP基因的转录物异常丰富。在本研究中，我们从韩国生态型拟南芥中分离了两个毛状体特异性LTP基因（AaLTP3和AaLTP4）。AaLTP3在芽中大量表达，而AaLTP4在花中表达。由AaLTP3或AaLTP4启动子驱动的GUS信号在转基因A. annua植物中显示，AaLTP3启动子在毛发状非GTs上有活性，而AaLTP4启动子在GTs上有活性。对转基因烟草中与AaLTP3或AaLTP4蛋白融合的增强型青色荧光蛋白（ECFP）荧光进行的分析显示，ECFP荧光在长GT分泌的脂质上非常明亮。此外，短毛状体及其分泌的颗粒的头细胞上的花序也很亮。桔梗叶柄中GT渗出液的免疫印迹分析显示，针对AaLTP4抗体有很强的阳性信号。与野生型相比，转基因A.annua植物中AaLTP3或AaLTP4的过表达导致倍半萜内酯（青蒿素B，青蒿素，二氢青蒿酸和青蒿酸）的产量提高。目前的研究表明，LTP基因（AaLTP3或AaLTP4）在金黄色葡萄球菌的GT脂质的螯合和分泌中起重要作用，