The long road of functional recruitment-The evolution of a gene duplicate to pyrrolizidine alkaloid biosynthesis in the morning glories (Convolvulaceae).

In plants, homospermidine synthase (HSS) is a pathway-specific enzyme initiating the biosynthesis of pyrrolizidine alkaloids (PAs), which function as a chemical defense against herbivores. In PA-producing Convolvulaceae ("morning glories"), HSS originated from deoxyhypusine synthase at least >50 to 75 million years ago via a gene duplication event and subsequent functional diversification. To study the recruitment of this ancient gene duplicate to PA biosynthesis, the presence of putative gene copies in 11 Convolvulaceae species was analyzed.

Development of an activity assay for characterizing deoxyhypusine synthase and its diverse reaction products.

Deoxyhypusine synthase transfers an aminobutyl moiety from spermidine to the eukaryotic translation initiation factor 5A (eIF5A) in the first step of eIF5A activation. This exclusive post-translational modification is conserved in all eukaryotes. Activated eIF5A has been shown to be essential for cell proliferation and viability.