Spatiotemporal deep imaging of syncytium induced by the soybean cyst nematode Heterodera glycines
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Parasite infections cause dramatic anatomical and ultrastructural changes in host plants. Cyst nematodes are parasites that invade host roots and induce a specific feeding structure called a syncytium. A syncytium is a large multinucleate cell formed by cell wall dissolution-mediated cell fusion. The soybean cyst nematode (SCN), Heterodera glycines, is a major soybean pathogen. To investigate SCN infection and the syncytium structure, we established an in planta deep imaging system using a clearing solution ClearSee and two-photon excitation microscopy (2PEM). Using this system, we found that several cells were incorporated into the syncytium; the nuclei increased in size and the cell wall openings began to be visible at 2 days after inoculation (DAI). Moreover, at 14 DAI, in the syncytium developed in the cortex, there were thickened concave cell wall pillars that resembled “Parthenon pillars.” In contrast, there were many thick board-like cell walls and rarely Parthenon pillars in the syncytium developed in the stele. We revealed that the syncytia were classified into two types based on the pattern of the cell wall structures, which appeared to be determined by the position of the syncytium inside roots. Our results provide new insights into the developmental process of syncytium induced by cyst nematode and a better understanding of the three-dimensional structure of the syncytium in host roots.
KeywordsPlant-parasitic nematode Heterodera Syncytium development Two-photon excitation microscopy (2PEM) Deep imaging
We thank Dr. S. Aiba (National Agriculture and Food Research Organization) and Prof. Dr. K. Kawakita (Nagoya University) for kindly providing cyst of H. glycines and Prof. Dr. M.G.K. Jones (Murdoch University) for kindly providing methods of plant-parasitic nematodes. This work was supported by a grant from the Integrative Graduate Education and Research Program in Green Natural Sciences of Nagoya University, the Japan Society for the Promotion of Science (JSPS) Fellowship (15J04623 for M. O.), the Japan Advanced Plant Science Research Network, the JSPS Grant-in-Aid for challenging Exploratory Research (15K14542 for Y. S., 15K14541 for D. M.), the Japan Science and Technology Agency (ERATO project to T. H.), Toyoaki Scholarship Foundation (for D. M.), the JSPS Grant-in-Aid for Young Scientists (A) (16H06173 for D. M.), and the JSPS KAKENHI (16H06465 for T. H.).
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Conflict of interest
The authors declare that they have no conflict of interest.
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