Isolation and characterization of ZePES and AtPES, the pescadillo orthologs from Zinnia and Arabidopsis

The pescadillo gene was originally identified and characterized through a mutational screen in zebrafish, Danio rerio, affecting embryonic development. Subsequent reports have shown that the yeast and animal homologs are implicated in ribosome biogenesis, cell cycle progression and carcinogenesis, while disruption of its function leads to growth arrest. At present, no orthologs of the pescadillo gene have been characterized in plants. Here we report, for the first time, the isolation and characterization of the pescadillo orthologs from Zinnia elegans (ZePES) and Arabidopsis thaliana (AtPES). ZePES, which is expressed differentially throughout tracheary element differentiation of Zinnia mesophyll cells, is upregulated during G1/S and G2/M transition. Both ZePES and AtPES are able to complement the temperature-sensitive phenotype of yeast degron strain Y40047, impaired in the NOP7/YPH1 gene (pescadillo ortholog), indicating a functional conservation between the yeast and plant gene products. We also show that AtPES-GFP fusion protein is localized in the nucleolus of plant cells. Analysis of transgenic plants reveals that AtPES is expressed during vegetative and reproductive development predominantly in meristematic tissues and actively dividing cells, while overexpression of AtPES does not lead to any phenotypic changes during growth and development.