Nostadt Robin, Hilbert Magdalena, Nizam Shadab, Rovenich Hanna, Wawra Stephan, Martin Jörg, Küpper Hendrik, Mijovilovich Ana, Ursinus Astrid, Langen Gregor, Hartmann Marcus D, Lupas Andrei N, Zuccaro Alga
Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Str. 10, 35043, Marburg, Germany.
Cluster of Excellence on Plant Sciences (CEPLAS), Cologne Biocenter, Botanical Institute, University of Cologne, Zülpicher Str. 47b, 50674, Cologne, Germany.
New Phytol. 2020 Aug;227(4):1174-1188. doi: 10.1111/nph.16606. Epub 2020 May 16.
Like pathogens, beneficial endophytic fungi secrete effector proteins to promote plant colonization, for example, through perturbation of host immunity. The genome of the root endophyte Serendipita indica encodes a novel family of highly similar, small alanine- and histidine-rich proteins, whose functions remain unknown. Members of this protein family carry an N-terminal signal peptide and a conserved C-terminal DELD motif. Here we report on the functional characterization of the plant-responsive DELD family protein Dld1 using a combination of structural, biochemical, biophysical and cytological analyses. The crystal structure of Dld1 shows an unusual, monomeric histidine zipper consisting of two antiparallel coiled-coil helices. Similar to other histidine-rich proteins, Dld1 displays varying affinity to different transition metal ions and undergoes metal ion- and pH-dependent unfolding. Transient expression of mCherry-tagged Dld1 in barley leaf and root tissue suggests that Dld1 localizes to the plant cell wall and accumulates at cell wall appositions during fungal penetration. Moreover, recombinant Dld1 enhances barley root colonization by S. indica, and inhibits H O -mediated radical polymerization of 3,3'-diaminobenzidine. Our data suggest that Dld1 has the potential to enhance micronutrient accessibility for the fungus and to interfere with oxidative stress and reactive oxygen species homeostasis to facilitate host colonization.
与病原体一样，有益内生真菌会分泌效应蛋白来促进对植物的定殖，例如通过干扰宿主免疫。根内生真菌印度梨形孢的基因组编码了一个新的、高度相似的、富含丙氨酸和组氨酸的小蛋白家族，其功能尚不清楚。该蛋白家族成员带有一个N端信号肽和一个保守的C端DELD基序。在这里，我们结合结构、生化、生物物理和细胞学分析，报告了植物响应性DELD家族蛋白Dld1的功能特性。Dld1的晶体结构显示出一种不同寻常的单体组氨酸拉链，由两个反平行的卷曲螺旋组成。与其他富含组氨酸的蛋白相似，Dld1对不同的过渡金属离子表现出不同的亲和力，并经历金属离子和pH依赖性的去折叠。在大麦叶片和根组织中瞬时表达mCherry标记的Dld1表明，Dld1定位于植物细胞壁，并在真菌穿透过程中在细胞壁附着处积累。此外，重组Dld1增强了印度梨形孢对大麦根的定殖，并抑制了H₂O₂介导的3,3'-二氨基联苯胺的自由基聚合。我们的数据表明，Dld1有潜力增强真菌对微量营养素的可及性，并干扰氧化应激和活性氧稳态，以促进对宿主的定殖。
