Helm Matthew, Singh Raksha, Hiles Rachel, Jaiswal Namrata, Myers Ariana, Iyer-Pascuzzi Anjali S, Goodwin Stephen B
Crop Production and Pest Control Research Unit, U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), West Lafayette, IN 47907.
Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907.
Phytopathology. 2022 Dec;112(12):2538-2548. doi: 10.1094/PHYTO-05-22-0181-R. Epub 2022 Nov 17.
Most fungal pathogens secrete effector proteins into host cells to modulate their immune responses, thereby promoting pathogenesis and fungal growth. One such fungal pathogen is the ascomycete , which causes tar spot disease on leaves of maize (). Sequencing of the genome revealed 462 putatively secreted proteins, of which 40 contain expected effector-like sequence characteristics. However, the subcellular compartments targeted by effector candidate (PmEC) proteins remain unknown, and it will be important to prioritize them for further functional characterization. To test the hypothesis that PmECs target diverse subcellular compartments, cellular locations of super yellow fluorescent protein-tagged PmEC proteins were identified using a -based heterologous expression system. Immunoblot analyses showed that most of the PmEC-fluorescent protein fusions accumulated protein in , indicating that the candidate effectors could be expressed in dicot leaf cells. Laser-scanning confocal microscopy of epidermal cells revealed that most of the putative effectors localized to the nucleus and cytosol. One candidate effector, PmEC01597, localized to multiple subcellular compartments including the nucleus, nucleolus, and plasma membrane, whereas an additional putative effector, PmEC03792, preferentially labelled both the nucleus and nucleolus. Intriguingly, one candidate effector, PmEC04573, consistently localized to the stroma of chloroplasts as well as stroma-containing tubules (stromules). Collectively, these data suggest that effector candidate proteins from target diverse cellular organelles and could thus provide valuable insights into their putative functions, as well as host processes potentially manipulated by this fungal pathogen.
大多数真菌病原体向宿主细胞分泌效应蛋白以调节其免疫反应，从而促进发病机制和真菌生长。一种这样的真菌病原体是子囊菌，它会在玉米叶片上引起焦油斑病（）。对该基因组的测序揭示了462种可能分泌的蛋白质，其中40种具有预期的效应样序列特征。然而，效应候选（PmEC）蛋白靶向的亚细胞区室仍然未知，对它们进行优先级排序以进行进一步的功能表征将很重要。为了检验PmECs靶向不同亚细胞区室的假设，使用基于的异源表达系统鉴定了超黄色荧光蛋白标记的PmEC蛋白的细胞位置。免疫印迹分析表明，大多数PmEC-荧光蛋白融合体在中积累蛋白质，表明候选效应蛋白可以在双子叶植物叶细胞中表达。对表皮细胞的激光扫描共聚焦显微镜观察表明，大多数推定的效应蛋白定位于细胞核和细胞质。一种候选效应蛋白PmEC01597定位于多个亚细胞区室，包括细胞核、核仁和平膜，而另一种推定的效应蛋白PmEC03792则优先标记细胞核和核仁。有趣的是，一种候选效应蛋白PmEC04573始终定位于叶绿体的基质以及含基质的小管（stromules）。总体而言，这些数据表明来自的效应候选蛋白靶向不同的细胞器，因此可以为它们的推定功能以及这种真菌病原体可能操纵的宿主过程提供有价值的见解。
