Profiles of Physarum Microplasmodial Phosphatase Activity Crucial to Cytoplasmic Streaming and Spherule Formation
This study aimed to investigate for the first time, the profile of Physarum microplasmodial phosphatase (PPH) activity toward the phosphorylated light chain of Physarum myosin II (PLCM) at pH 7.6, the velocity of cytoplasmic streaming, and PPH expression in spherule formation during dark starvation (DS). In this study, we cloned the full-length cDNA of PPH using polymerase chain reaction, based on the N-terminal amino acid sequence of the purified enzyme. The cDNA contained an open reading frame (ORF) of 1245 bp, corresponding to 415 amino acids. We confirmed that a rapid increase in PPH activity toward PLCM and a rapid decrease in cytoplasmic streaming velocity precede spherule formation by Physarum microplasmodia. The profiles of increase in PPH activity toward PLCM, PPH expression, and PPH accumulation during DS were correlated with spherule formation in the Physarum microplasmodia. Moreover, application of the wheat germ cell-free expression system resulted in the successful production of recombinant PPH and in the expression of phosphatase activity toward PLCM. These results suggest that PPH is involved in the cessation of cytoplasmic streaming in Physarum microplasmodia during DS.
KeywordsCytoplasmic streaming Physarum polycephalum Microplasmodia Myosin II Spherule formation cDNA cloning
The authors would like to thank Dr Rumi Kaida (Tokyo University of Agriculture) for performing the homology search of the PPH amino acid sequence against the online database. We would like to thank Editage (www.editage.jp) for English language editing.
This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (nos. 23590295 and 15K00809 to A.N.; no. 26670128 to K.K.) and by a grant from the Smoking Research Foundation.
C.Y.O. is the main executor of this work. C.Y.O., A.N., K.O., K.K. and T.S.K. performed this research. C.Y.O., A.N. and T.S.K. designed the research study. A.N. and K.K. provided funding. C.Y.O. and T.S.K. wrote the paper mainly.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
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