Media Coverage Back to Home Page

Printer Friendly Version

ABSTRACT FROM PLANT CANADA 2005 - Promoter activities of deoxyhypusine synthase and eukaryotic translation initation factor 5A1 in Arabidopsis thaliana suggest a role in xylogenesis, leaf senescence and flower senescence

DUGUAY, J.L., WANG, T-W., ZHANG, C.,

THOMPSON, J.E.

Univ of Waterloo, Dept. of Biology, Waterloo,

ON. N2L 3G1

Numerous reports have documented the importance of deoxyhypusine synthase (DHS) and eukaryotic translation initiation factor 5A (eIF-5A) in human cell proliferation and apoptosis. However, relatively little attention has been given to their plant kingdom counterparts, despite their ubiquitous presence and highly conserved sequences. DHS activates eIF-5A by modifying a conserved lysine to the unusual amino acid hypusine, in one of the most specific post-translational modifications discovered to date. Recent evidence shows there are multiple isoforms of eIF-5A and it is believed that each functions as a shuttle protein, responsible for transporting a specific subset of mRNAs (either proliferationrelated or senescence-related) from the nucleus to the cytoplasm for translation. To further elucidate the roles of DHS and eIF -5A1, one of three eIF -5A isoforms in Arabidopsis, the promoter activities of both were characterized during growth and development of transgenic Arabidopsis plants using GUS as a reporter gene. The levels of DHS::GUS and eIF-5A1::GUS expression were strongly upregulated at the onset of leaf senescence, and this high expression was maintained until leaf senescence terminated. Furthermore, and unexpectedly, DHS and eIF -5A1 were transiently and co-ordinately expressed in the vascular tissues of developing cotyledons, rosette leaves and stems. The timing and localization of the GUS expression imply a role for eIF-5A1 in xylogenesis. In addition, DHS and eIF -5A1 were co-ordinately expressed in anther tissues during the degenerative stages of pollen production. Taken together, these results suggest that DHS and eIF -5A1 regulate programmed cell death associated withxylogenesis, leaf senescence and flower senescence in Arabidopsis.