Final Activity Report Summary - STAR (Stem cell activity in arabidopsis) In plants, all the post-embryonic cells are derived from structures called meristems. These meristems are formed of a small number of stem cells surrounded by a pool of undifferentiated cells. These structures are highly regulated being critical, among other processes, for the balance between cell division and cell differentiation.We have been interested in similarities in the function of plant and animal stem cells. The starting point for this project was the comparison of conserved genes that are preferentially expressed in animal stem cell cultures and in plant meristems. One of the genes identified as a candidate to perform functions relevant both to the meristem and to animal stem cells was APACD. The remainder of the project focused on revealing the function of APACD in Arabidopsis.Although the APACD protein is predicted to be a non canonical thioredoxin, it showed thioredoxin activity in vitro. Ectopically expressing APACD transgenic plants caused hypersensitivity to DNA damage and to oxidative stress, whereas inhibition by RNAi caused both male and female gametophytic lethality. In addition to this phenotype, a different RNAi line showed larger cells and aneuploidy, suggesting defects in spindle function. Together, the data suggest that APACD could link DNA damage with cell division. Current work aims to test the role of APACD in spindle formation and to understand the basis for the hypersensitivity to DNA damage seen in the overexpression lines.
