Variations of Proline Rich Cell Wall Proteins in Soybean Lines with
Anthocyanin Mutations
Christopher D. Nicholas, John T. Lindstrom, & Lila O. Vodkin
Abstract
TheI locus controls inhibition of anthocyanin accumulation in the
epidermal cells of the soybean seed coat and affects abundance of PRP1,
a proline-rich cell wall protein in the seed coat. Saline-soluble PRP1
is abundant in the developing seed coats of cultivar Richland
(homozygous I, yellow), while it is significantly decreased in
the pigmented isogenic mutant T157 (homozygous i, imperfect
black). In this report we examined soluble PRP1 in several culitvars
containing alleles of the I locus which affect spatial
distribution of pigmentation in the seed coat. We also characterized
PRP1 in isolines which allelic variations of several other loci involved
in seed coat pigmentation, including T and Im . The T
gene is pleiotropic and affects both pubescence color and seed coat
pigmentation and structure. Soluble PRP1 was abundant in the developing
seed coat of lines with yellow seed (I or i-i alleles)
regardless pubescence color, just as in Richland. Likewise, soluble PRP1
was decreased in pigmented seed coats (i-k or i alleles)
with grey (t ) pubescence, as in T157. However, the total seed
coat proteins were not extractable from pigmented with tawny pubescence
(i , T genotype) because they have proanthocyanidins that
exhibit tannin properties. The dominant Im allele inhibits seed
coat mottling (irregular patches of pigmentation) that occurs if plants
are infected with soybean mosaic virus. PRP1 was 35 kDa in mottled
(im ) isolines and 34 kDa in non-mottled (Im ) isolines.
PRP2, which is expressed later in seed coat development and in the
hypocotyl hooks of soybean seedlings, was also smaller in Im
isolines. In summary, some anthocyanin mutations affect the quantity of
soluble PRP1 polypeptides, while others correlate with structural
changes in developmentally regulated proline-rich proteins.