Organization of the R chromosome region in maize
Alleles of R govern the presence, intensity and time of anthocyanin pigmentation, plant part by plant part. A given allele often comprises more than one unit of independent function. One objective has been to characterize alleles in terms of genic element composition. What is the number, arrangement and tissue-specific domain of the elements comprising particular alleles were the questions posed. Various patterns of organization have been uncovered among alleles carried in cultivated races of maize. Some especially complex alleles have yet to be resolved fully in these terms. New patterns of organization undoubtedly remain to be discovered. We nevertheless relegated this line of inquiry to a position of secondary emphasis over the course of the past three years. Primary attention was shifted to analysis of individual genic elements. Two approaches utilize given elements which have been fractionated from allelic complexes or which occur singly in cultivated races. Recombinational tests of single element heterozygotes focuses on the components which confer tissue specific differences. An alternative approach makes use of phenotypically null mutations of single element alleles. Such are combined in heterozygotes with elements of contrasting tissue effect to recombine a functional form of the mutant allele. The resynthesis of elements in this manner appears to provide a systematic means of identifying components that are essential for an element's function but which are not responsible for its tissue specific action. The nature of genetic instabilities continues as another major area of interest. The kernel-spotting allele R-stippled is associated with two sorts of instabilities. Its somatic and germinal reversion to uniform strong color is attributable to a transposable unit. Its capacity to reduce the functional level of sensitive alleles in heterozygotes (paramutation) has a different basis. Organization of its paramutagenic potential is reported.
- Research Organization:
- Wisconsin Univ., Madison (USA)
- DOE Contract Number:
- AC02-76EV01300
- OSTI ID:
- 6149163
- Report Number(s):
- DOE/EV/01300-T1; ON: DE83008329
- Resource Relation:
- Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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