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ARS Home » Midwest Area » Columbia, Missouri » Plant Genetics Research » Research » Publications at this Location » Publication #59118
Title: ALLELIC INTERACTIONS HERITABLY ALTER THE ACTIVITY OF A METASTABLE MAIZE PL ALLELE

Author
item HOLLICK, JAY - UNIV OF OREGON
item PATTERSON, GARTH - UNIV OF OREGON
item Coe Jr, Edward
item CONE, KAREN - UNIV OF MISSOURI
item CHANDLER, VICKI - UNIV OF OREGON

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Regulatory genes, which activate or moderate the activity of groups of genes to control sets of coherent functions, are central in current genetic studies because their roles are 'managerial'. That is, they determine that necessary things are done or not done in concert. The present study identifies and defines, for a gene of this type, spontaneous origination of non-conventional inheritance. On their face, aspects of this inheritance behavior are inconsistent with the Mendelian Law that genes received from two parents do not alter each other and separate from each other into the gametes and into progeny. The non-conventional phenomenon, termed paramutation, has been found for only two other genes in corn, both of which are also regulatory. The new information is that the features for this gene bridge between those of the other two, and indicate that the mechanisms are likely in common among the three genes. Toward an explanation in molecular/biochemical terms, the commonality points to a single basis and simplifies the research models that must be examined. The occurrence of this behavior in a class of regulatory genes where it had not previously been found, suggests that the phenomenon may be a special property of regulatory genes.

Technical Abstract: The maize pl locus encodes a mby-like transcriptional activator of anthocyanin biosynthetic genes. Strong activity of the Pl-Rhoades (Pl-Rh) allele confers robust purple anthocyanin pigment in several mature plant tissues. This allele exhibits an unusual behavior, documented in this report. Spontaneous derivatives of Pl-Rh arise that confer reduced anthocyanin pigment and are meiotically heritable; these derivatives are termed Pl'-mahogany (Pl'-mah). Coincident with the reduction in pigment accumulation, these derivatives interact with other Pl-Rh alleles such that only Pl'-mah alleles are transmitted from a Pl-Rh/Pl'-mah heterozygote. Mendelian segregation of marked chromosomes establishes that chromosomal segregation distortion is not the cause of this exclusive transmission and leads to the interpretation that Pl-Rh invariable changes to Pl'-mah in the presence of Pl'-mah. Such behavior is a hallmark of paramutation. Co- segregation experiments demonstrate that this paramutagenic activity is generally linked to the pl locus. By visually quantifying pl action through successive crosses we find that phenotypic expression is inversely related to paramutagenic strength. We also find that the paramutagenic state is metastable; reversion to a non-paramutagenic Pl-Rh state can occur under certain circumstances. The behavior of Pl-Rh is unique, yet is shares characteristics with paramutation behavior at two other maize loci, b and r. Previous analysis of b and r paramutation revealed extensive differences and led to suggestions that distinct molecular mechanisms were operating. Consideration of the common features shared by all three systems reinvigorates the interpretation that the mechanistic processes of these allelic interactions are similar at all three loci.