EXPRESSION AND ACCUMULATION PATTERNS OF NITROGEN-RESPONSIVE LIPOXYGENASE IN SOYBEANS

Gene expression and protein accumulation patterns of nitrogen responsi ve lipoxygenase (LOX-NR), as a representative vegetative storage prote in, were investigated in nonnodulated soybeans (Glycine max [L.] Merr. cv Wye). The form of available nitrogen (supplied as NH4NO3, NH4+, NO 3-, or urea) influenced the mRNA level and the amount of LOX protein, indicating that preferential accumulation of LOX may occur. Soybeans w ere grown with 0, 2, 5, and 16 mm total nitrogen to determine the exte nt to which LOX accumulation responded to soil nitrogen levels. Analys is of both mRNA and protein levels was conducted in shoot tips, stems, pod walls, and leaves over the entire life cycle of the plant. A gene ral correlation between increasing available nitrogen level and LOX le vel was seen in the shoot tip and other organs throughout the soybean life cycle. However, appreciable amounts of LOX-NR mRNA and protein ac cumulated even when plants were grown under conditions of nitrogen def iciency. The results indicate that LOX may play an important role as a temporary storage site for amino acids in the developing shoot tip. T he expression patterns of LOX-NR in plants grown under nitrogen defici ency suggest that these proteins, although responsive to nitrogen stat us, may not function solely as temporary storage pools for amino acids .