Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, 35043, Marburg, Germany.
New Phytol. 2018 Oct;220(2):553-566. doi: 10.1111/nph.15268. Epub 2018 Jun 13.
The peroxisomal sterol carrier protein 2 (Scp2) of the biotrophic maize pathogen Ustilago maydis was detected in apoplastic fluid, suggesting that it might function as a secreted effector protein. Here we analyze the role of the scp2 gene during plant colonization. We used reverse genetics approaches to delete the scp2 gene, determined stress sensitivity and fatty acid utilization of mutants, demonstrated secretion of Scp2, used quantitative reverse transcription polymerase chain reaction for expression analysis and expressed GFP-Scp2 fusion proteins for protein localization. scp2 mutants were strongly attenuated in virulence and this defect manifested itself during penetration. Scp2 localized to peroxisomes and peroxisomal targeting was necessary for its virulence function. Deletion of scp2 in U. maydis interfered neither with growth nor with peroxisomal β-oxidation. Conventionally secreted Scp2 protein could not rescue the virulence defect. scp2 mutants displayed an altered localization of peroxisomes. Our results show a virulence function for Scp2 during penetration that is probably carried out by Scp2 in peroxisomes. We speculate that Scp2 affects the lipid composition of membranes and in this way ensures the even cellular distribution of peroxisomes.
玉米生物型病原菌构巢曲霉的过氧化物酶体固醇载体蛋白 2（Scp2）被检测到存在于质外体流体中，这表明它可能作为一种分泌效应蛋白发挥作用。在这里，我们分析了 scp2 基因在植物定殖过程中的作用。我们使用反向遗传学方法删除 scp2 基因，确定了突变体的应激敏感性和脂肪酸利用情况，证明了 Scp2 的分泌，使用定量逆转录聚合酶链反应进行表达分析，并表达 GFP-Scp2 融合蛋白进行蛋白质定位。scp2 突变体在毒力方面明显减弱，这种缺陷在穿透过程中表现出来。Scp2 定位于过氧化物酶体，过氧化物酶体靶向对于其毒力功能是必要的。U. maydis 中 scp2 的缺失既不影响生长，也不影响过氧化物酶体β-氧化。常规分泌的 Scp2 蛋白不能挽救毒力缺陷。scp2 突变体显示过氧化物酶体的定位发生改变。我们的结果表明，Scp2 在穿透过程中具有毒力功能，可能是通过过氧化物酶体中的 Scp2 发挥作用。我们推测 Scp2 影响膜的脂质组成，从而确保过氧化物体的均匀细胞分布。
