Mitotic stopwatch for the blast fungus Magnaporthe oryzae during invasion of rice cells

To study nuclear dynamics of Magnaporthe oryzae, we developed a novel mitotic reporter strain with GFP-NLS (localized in nuclei during interphase but in the cytoplasm during mitosis) and H1-tdTomato (localized in nuclei throughout the cell cycle). Time-lapse confocal microscopy of the reporter strain during host cell invasion provided several new insights into nuclear division and migration in M. oryzae: (i) mitosis lasts about 5 min; (ii) mitosis is semi-closed; (iii) septal pores are closed during mitosis; and (iv) a nucleus exhibits extreme constriction (approximately from 2 μm to 0.5 μm), elongation (over 5 μm), and long migration (over 16 μm). Our observations raise new questions about mechanisms controlling the mitotic dynamics, and the answers to these questions may result in new means to prevent fungal proliferation without negatively affecting the host cell cycle.