Identification and characterization of chemical inhibitors of reprogramming process in Physcomitrella patens and Arabidopsis thaliana

Abstract

In the moss Physcomitrella patens, differentiated leaf cells of an excised leaf change to protonemal apical stem cells without exogenous phytohormones, which provides an outstanding experimental system for the study of molecular basis of reprogramming process in plants. To clarify this, we tried to screen the chemical compounds inhibiting the reprogramming process from a leaf cell to an apical stem cell. Of 12,000 chemicals, 4 chemicals were isolated as the reprogramming inhibitors, which all show (1) inhibition of the protrusion of protonema from a leaf, (2) lower effect to the protonemal growth, and (3) inhibition of expression of cell-cycle reentry marker gene CYCD;1 and protonema-specific marker gene RM09. Further characterization revealed that RIN16B, one of the reprogramming inhibitors, also inhibits the lateral-root development in Arabidopsis thaliana. With this system, we further isolated RIN16B-resistant lines from Arabidopsis FOX lines to elucidate the molecular mechanism downstream of RIN16B.