Accumulation of noncrystalline cellulose in Physarum microplasmodia

Physarum plasmodium lives as a slimy mass of protoplast in the dark fragments into small multinucleated microplasmodia (mPL) in a liquid medium. When mPL are exposed to several unfavorable environments, they transform into “spherules” with a cell wall. Using a synchronous spherule-induction system for mPL, we examined the effect of 2,6-dichlorobenzonitrile on the synthesis of cellulose in mPL, by observing mPL under a fluorescence microscope, and isolated cellulose from mPL to identify them morphologically under scanning electron microscopy. Moreover, we examined in vivo labeling to determine when cellulose synthesis is activated in step 2. We found that the nourishment medium in step 2 was essential for mPL prior to spherulation and that the conversion starts at 48 h in step 2 of our system. From the experiments using Updegraff reagent for the sedimentation of cellulose in the cell wall fraction from mPL, we propose that cellulose produced in mPL is likely noncrystalline cellulose. We conclude that mPL of multinucleated protoplasts without the cell wall structure synthesize cellulose under constitutive condition and accumulate abundantly noncrystalline cellulose, in preparation for unfavorable environments that may occur in the future in which mPL must initiate the program to form the cell wall of spherules.