Abstract
Arabidopsis LSD1 and LOL1 are negative and positive regulator of cell death, respectively, and interact with same transcription factors involved in the induction of cell death via "GxP" motif. Both LSD1 and LOL1 have zinc-finger motifs required for protein-protein interaction, but only LSD1 has an extended C-terminal region, which is highly conserved among LSD1 homologues in other plants. To clarify the regulatory mechanism of cell death by both LSD1 and LOL1, the functional analysis was done by focusing on C-terminal domain of LSD1 (LSD1C). LOL1+LSD1C could complement the cell death phenotype in lsd1-2, which was not by LOL1 alone. This result indicated that presence or absence of LSD1C would be a key to determine the function of LSD1 and LOL1 on regulatory mechanism of cell death. Since LSD1 homologues in other plants also interact with same Arabidopsis transcription factor via "GxP" motif, the function of LSD1 homologues might be regulated by same mechanism as in Arabidopsis. The repression of protein degradation of LSD1 by a proteasome inhibitor suggested that the proteasome-mediated degradation mechanism also involves in the regulatory mechanism of cell death mediated by LSD1.
