Antimicrobial coumarins and proteins to functionalizing the leaf surface for plant protection

大豆是世界上最重要的农作物之一。其主要病害是亚洲大豆锈病（SBR），由真菌Phakopsora pachyrhizi引起。在主要的大豆种植区（巴西、阿根廷和美国），SBR每年造成数十亿欧元的产量损失。目前还没有抗黄豆的优良品种，而且栽培方法以及化学或生物防治措施无效、昂贵或可能有害。因此，需要采取其他措施来控制SBR。我们之前的研究表明，向日葵和拟南芥对SBR的有效非寄主抗性可能是由于东莨菪碱的积累。香豆素能有效抑制肿根菌孢子的萌发。然而，东莨菪碱似乎不存在于大豆中。重建东莨菪碱生物合成的转基因大豆植株对SBR的易感性略有降低。但是，高浓度的东莨菪碱损害了植物。因此，我们希望将向日葵的非寄主抗性转移到大豆上，通过在叶片表面分泌东莨菪碱，在不伤害植物的情况下有效地对抗肿根菌孢子。我们打算对异东莨菪素做同样的研究，与其他香豆素相比，异东莨菪素在光照下非常稳定，可以有效地对抗肿根菌孢子。此外，我们旨在重建转基因植物中黄豆苷的生物合成并研究其作用方式。最后，在一种互补的方法中，我们想要合成并分泌到叶片表面的抗菌蛋白，这些蛋白有助于向日葵对SBR的非寄主抗性。表面积累抗菌香豆素和/或蛋白质的大豆植物有望在全球范围内实现可持续的大豆生产。

Soybean is one of the most important crops worldwide. Its major disease is Asian soybean rust (SBR) that is caused by the fungus Phakopsora pachyrhizi. In the major soybean-growing areas (Brazil, Argentina, and the USA), SBR causes annual yield losses of several billion Euros a year. Resistant elite varieties of the soybean are not available and cultivation practices as well as chemical or biological control measures ineffective, expensive, or potentially harmful. Therefore, alternative measures for SBR control are needed. We previously showed that the effective nonhost resistance of sunflower and Arabidopsis to SBR could be due to the accumulation of scopoletin. The coumarin effectively inhibits the germination of P. pachyrhizi spores. Scopoletin, however, seems to be absent from soybean. Reconstituting scopoletin biosynthesis in transgenic soybean plants slightly reduced the susceptibility to SBR. But, high scopoletin concentrations damaged the plants. We, therefore, would like to transfer the nonhost resistance of sunflower to soybean by secreting scopoletin to the leaf surface to effectively fight P. pachyrhizi spores without harming the plant. We intend to do the same for isoscopoletin, that in contrast to other coumarins is very stable in the light and effectively fights P. pachyrhizi spores. In addition, we aim to reconstitute the biosynthesis of sideretin in transgenic plants and investigate its mode of action. Finally, in a complementary approach we would like to synthesize and secrete to the leaf surface antimicrobial proteins that contribute to sunflower nonhost resistance to SBR. Soybean plants that surface-accumulate antimicrobial coumarins and/or proteins are promising for sustainable worldwide soybean production.