On the Cover: Homospermidine synthase is the first specific enzyme in the biosynthesis of pyrrolizidine alkaloids. Pyrrolizidine alkaloids are typical compounds of plant secondary metabolism and are produced within Senecio spp. plants in the roots. They are translocated through the phloem to the shoot, where these alkaloids are accumulated as part of the plant's chemical defense against herbivores. Homospermidine synthase evolved from deoxyhypusine synthase, an enzyme of primary metabolism that is involved in the posttranslational activation of the eukaryotic initiation factor 5A (eIF5A). In this issue, Moll et al. (pp. 47–57) report the localization of homospermidine synthase in comparison with its ancestor deoxyhypusine synthase. While deoxyhypusine synthase seems to be expressed in all tested tissues of S. vernalis, expression of homospermidine synthase is restricted to groups of specific cells of endodermis and neighboring cells of cortex parenchyma opposite the phloem. The cover shows a cross section of an S. vernalis root labeled with an affinity-purified antibody specific for homospermidine synthase using fluorescein isothiocyanate for detection with ultraviolet light. The phloem is located in between the three radially arranged ridges of the xylem that show intensive yellow autofluorescence due to lignification.