THE PLANT CELL, Vol 3, Issue 6 561-571, Copyright © 1991 by American Society of Plant Biologists
A Soybean Cell Wall Protein Is Affected by Seed Color Genotype
J. T. Lindstrom and L. O. Vodkin
Department of Agronomy, University of Illinois, Urbana, Illinois 61801
The dominant I gene inhibits accumulation of anthocyanin pigments in
epidermal cells of the soybean seed coat. We compared saline-soluble
proteins extracted from developing seed coats and identified a
35-kilodalton protein that was abundant in Richland (genotype I/I, yellow)
and much reduced in an isogenic mutant line T157 (genotype i/i, imperfect
black seed coats). We purified the 35-kilodalton protein by a novel
procedure using chromatography on insoluble polyvinylpolypyrrolidone. The
35-kilodalton protein was composed primarily of proline, hydroxyproline,
valine, tyrosine, and lysine. Three criteria (N-terminal amino acid
sequence, amino acid composition, and sequence of a cDNA) proved that the
seed coat 35-kilodalton protein was PRP1, a member of a proline-rich gene
family expressed in hypocotyls and other soybean tissues. The levels of
soluble PRP1 polypeptides and PRP1 mRNA were reduced in young seed coats
with the recessive i/i genotype. These data demonstrated an unexpected and
novel correlation between an anthocyanin gene and the quantitative levels
of a specific, developmentally regulated cell wall protein. In contrast,
PRP2, a closely related cell wall protein, was synthesized later in seed
coat development and was not affected by the genotype of the I locus.
