The changing peroxidase polymorphism in Lupinus albus during vegetative development

Abstract

Analyses of 14 samples representing organs in different stages of skotomorphogenic and photomorphogenic development, and the iterative growth from both root and shoot apical meristems, showed preliminary evidence for the operation of at least six different peroxidase groups showing differential patterns of activity during vegetative development. These included two acidic forms, a neutral-basic form and three highly basic forms. While no peroxidase group was organ specific or restricted to either the skotomorphogenic or photomorphogenic developmental pathways, clear and similar qualitative changes in peroxidase polymorphism occurred during the maturation of several different organs. This suggested that a developmental program regulating the changing isoperoxidase content in vegetative development was common to several organs in Lupinus albus. The subcellular locations, tissue specificity and spatial distribution of individual peroxidase groups in etiolated hypocotyls were related to the spatial location of active elongation and a marker of lignification, the isoperoxidase A2. Individual isoperoxidases could be associated with the developmental phases of either (a) pre-elongation, (b) active elongation, (c) restricted elongation and (d) active lignification. The possible functions of these peroxidases are discussed, and we present our selection of the peroxidase groups associated with the early phases of vegetative development for further studies and purification. Those selected include a highly soluble basic peroxidase (B5, pI 9.3) which appears to be largely restricted to the apoplast of juvenile tissues prior to the onset of active cellular elongation, and an ionically bound, basic peroxidase (B6, pI 9.7) of the epidermal apoplast which has a distribution strongly correlated to the reduction in cellular elongation along the hypocotyl axis.