PLANT PHYSIOLOGY , Vol 103, Issue 2 457-466, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Expression and Accumulation Patterns of Nitrogen-Responsive Lipoxygenase in Soybeans
H. D. Grimes, T. J. Tranbarger and V. R. Franceschi
Department of Botany, Washington State University, Pullman, Washington 99164-4238
Gene expression and protein accumulation patterns of nitrogen-responsive
lipoxygenase (LOX-NR), as a representative vegetative storage protein, were
investigated in nonnodulated soybeans (Glycine max [L.] Merr. cv Wye). The
form of available nitrogen (supplied as NH4NO3, NH4+, NO3-, or urea)
influenced the mRNA level and the amount of LOX protein, indicating that
preferential accumulation of LOX may occur. Soybeans were grown with 0, 2,
5, and 16 mM total nitrogen to determine the extent to which LOX
accumulation responded to soil nitrogen levels. Analysis 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 general correlation between
increasing available nitrogen level and LOX level was seen in the shoot tip
and other organs throughout the soybean life cycle. However, appreciable
amounts of LOX-NR mRNA and protein accumulated even when plants were grown
under conditions of nitrogen deficiency. The results indicate that LOX may
play an important role as a temporary storage site for amino acids in the
developing shoot tip. The expression patterns of LOX-NR in plants grown
under nitrogen deficiency suggest that these proteins, although responsive
to nitrogen status, may not function solely as temporary storage pools for
amino acids.
