von Sivers Lea, Jaspar Hannah, Johst Bettina, Roese Michael, Bitterlich Michael, Franken Philipp, Kühn Christina
Plant Physiology, Institute of Biology, Humboldt University of Berlin, Berlin, Germany.
Leibniz-Institute of Vegetable and Ornamental Crops, Großbeeren, Germany.
Front Plant Sci. 2019 May 15;10:571. doi: 10.3389/fpls.2019.00571. eCollection 2019.
Together with several proteins involved in brassinosteroid (BR) signaling and synthesis, the membrane steroid binding protein 1 (MSBP1) was identified within the interactome of the sucrose transporter of tomato (SlSUT2). We asked whether MSBP1 is also involved in BR signaling as assumed for the AtMSBP1 protein from Arabidopsis and whether it impacts root colonization with arbuscular mycorrhizal (AM) fungi in a similar way as shown previously for SlSUT2. In addition, we asked whether brassinosteroids affect efficiency of root colonization by AM fungi. We carried out a set of experiments with transgenic tobacco plants with increased and decreased MSBP1 expression levels. We investigated the plant and the mycorrhizal phenotype of these transgenic plants and tested the involvement of MSBP1 in BR metabolism by application of epi-brassinolide and brassinazole, an inhibitor of BR biosynthesis. We show that the phenotype of the transgenic tobacco plants with increased or reduced expression is consistent with an inhibitory role of MSBP1 in BR signaling. overexpression could be mimicked by brassinazole treatment. Interestingly, manipulation of expression in transgenic tobacco plants not only affected plant growth and development, but also the host plant responses toward colonization with AM fungi, as well as arbuscular architecture. Moreover, we observed that brassinosteroids indeed have a direct impact on the nutrient exchange in AM symbiosis and on the biomass production of colonized host plants. Furthermore, arbuscular morphology is affected by changes in expression and brassinolide or brassinazole treatments. We conclude that host plant growth responses and nutrient exchange within the symbiosis with AM fungi is controlled by brassinosteroids and might be impeded by the MSBP1 protein.
与几种参与油菜素内酯（BR）信号传导和合成的蛋白质一起，膜类固醇结合蛋白1（MSBP1）在番茄蔗糖转运蛋白（SlSUT2）的相互作用组中被鉴定出来。我们研究了MSBP1是否也像拟南芥中的AtMSBP1蛋白一样参与BR信号传导，以及它是否像之前对SlSUT2的研究那样，以类似的方式影响丛枝菌根（AM）真菌对根的定殖。此外，我们还研究了油菜素内酯是否影响AM真菌对根的定殖效率。我们用MSBP1表达水平升高和降低的转基因烟草植株进行了一系列实验。我们研究了这些转基因植株的植物和菌根表型，并通过施加表油菜素内酯和油菜素唑（一种BR生物合成抑制剂）来测试MSBP1在BR代谢中的作用。我们发现，MSBP1表达增加或减少的转基因烟草植株的表型与MSBP1在BR信号传导中的抑制作用一致。油菜素唑处理可以模拟MSBP1的过表达。有趣的是，转基因烟草植株中MSBP1表达的改变不仅影响植物的生长发育，还影响宿主植物对AM真菌定殖的反应以及丛枝结构。此外，我们观察到油菜素内酯确实对AM共生中的养分交换和定殖宿主植物的生物量生产有直接影响。此外，丛枝形态受到MSBP1表达变化以及油菜素内酯或油菜素唑处理的影响。我们得出结论，宿主植物的生长反应以及与AM真菌共生中的养分交换受油菜素内酯控制，并且可能受到MSBP1蛋白的阻碍。
