SEASONAL EXPRESSION PATTERNS AND CHARACTERIZATION OF A EUPHORBIA-ESULA ROOT STORAGE PROTEIN

High-abundance, water-soluble root proteins are hypothesized to be pot ential storage forms of reduced N assimilate in perennial weeds. Rabbi t antiserum raised against an electrophoretically purified 29 kDa root protein of leafy spurge (Euphorbia esula L.) was used to follow seaso nal protein accumulation patterns as well as responses to photoperiod and decapitation. Accumulation of the protein in roots of field-grown plants began during late spring months, with maximal accumulation obse rved during fall and winter months. Protein accumulation patterns over an 8-week period were similar in root extracts from controlled-enviro nment long- and short-day-grown plants at 30 degrees C. Decapitation o f the shoot resulted in an immediate decline of the 29 kDa protein in the roots, followed by a gradual increase as shoots expanded from root buds over a 4-week period. These accumulation patterns suggest that d ormant leafy spurge root buds may exploit the degradation of stored N root reserves in the form of soluble storage proteins for amino acids to fuel expansion and growth when the buds are released from apical do minance and the root undergoes a transition from sink to source. Proce sses controlling the accumulation or remobilization of such perennial root storage proteins thus provide potential targets for chemical or b iological weed control agents.