Invasive Growth of in Rice and Increase of Nuclear Number

Background: 'Rice ' is a solid culture of on steamed rice grains. Multiple parallel fermentation, wherein saccharification of rice by and alcohol fermentation by the budding yeast occur simultaneously, leads to the formation of a variety of ingredients of Japanese sake. In sake brewing, the degree of mycelial invasive growth into the steamed rice, called '-', highly correlates with the digestibility and quality of rice , since the hyphae growing into the rice secrete amylases and digest starch.

Results: In this study, we investigated mycelial distribution of GFP-tagged in rice made with different types of rice, such as sake rice and eating rice, with 50 or 90% polishing rate to remove abundant proteins and lipids near the surface. In addition, we compared transcriptomes of in the different types of rice . Finally, we found that increases the nuclear number and hyphal width in the course of 1-3 days cultivation.

Conclusions: Our imaging analyses indicate that hyphae grew more deeply into 50% polished rice than 90% polished rice. The increases of nuclear number may be a selectively acquired characteristic for the high secretory capacity during the long history of cultivation of this species.