Somatic Analysis of an Unstable Mutation for Anthocyanin Pigmentation in Soybean

Publisher Website
Google Scholar
Abstract
Most plants of the Asgrow Mutable line of soybean (Glycine max [L.] Merr.) are chimeric for anthocyanin pimentation. This line carries an unstable recessive (“mutable”) allele of the w4 locus. The mutable allete reverts at high frequency from the recessive form to a stable dominant form. Nonrevertant flowers on mutable plants exhibit the near-white phenotype typical of plants homozygous recessive at the w4 locus. Mutable plants produce both entirely near-white and entirely purple flowers as well as flowers of a mutable phenotype with purple sectors on near-white petals. Similarly, hypocotyls of mutable plants have purple flecks and stripes on an otherwise green background. The size of revertant sectors on mutable plants is dependent on the developmental timing of reversion of the mutable allele. Germinal reversion of the mutable allele is evidenced by the production of wild-type progeny by mutable plants. Histological examination revealed that expression of anthocyanin genes in the flower and other plant parts is cell-layer-specific. It was therefore possible to detect periclinal chimeras that result from reversion in the independent cell layers. Different types of periclinal chimeras were used to demonstrate that the germ line in soybean is of subepidermal origin. The instability of the mutable allele may represent the first genetic evidence of a transposable element in soybean that has inserted at the w4 locus.