The molecular basis of seed coat pigmentation in Glycine max
Todd, Joselyn Joy
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Permalink
https://hdl.handle.net/2142/21688
Description
Title
The molecular basis of seed coat pigmentation in Glycine max
Author(s)
Todd, Joselyn Joy
Issue Date
1995
Doctoral Committee Chair(s)
Vodkin, Lila O.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Biology, Molecular
Language
eng
Abstract
Seed coat color in Glycine max is determined by the classically defined I locus which controls the presence or absence, as well as the spatial distribution of anthocyanin pigments in the seed coat. Commercially used soybean cultivars have yellow seed coats due to the presence of either the I or $i\sp i$ allele of the I locus. Spontaneous mutations from these alleles have given rise to pigmented seed coats (i) which have been preserved in the form of near isogenic lines. RFLP analysis conducted on near isogenic lines differing only in respect to the alleles at the I locus has shown that the dominant I allele (giving rise to yellow seed coats) can be associated with a 12.1 kb Hind III polymorphism related to CHS1 of the chalcone synthase (CHS) multigene family. Additionally, in many cases, mutations from the $i\sp i$ allele to the recessive i allele can be associated with the absence of a 2.3 kb Hind III CHS fragment which represents CHS4. Moreover, analysis of these mutations via PCR based mapping has shown that there is a mutation in the CHS4 promoter region. Linkage analysis conducted between two F2 populations segregating for seed coat color has shown that there is co-segregation between the I locus alleles and CHS polymorphisms as detected by RFLP and PCR. Additionally, northern blot analysis has shown that heterozygotes (I/i; yellow seed coats) have reduced levels of CHS expression suggesting that the CHS polymorphism associated with dominant I allele inhibits CHS expression. Finally, CHS gene specific expression in seed coats was assessed via RT-PCR and cDNA cloning. Results of this analysis suggest that multiple CHS genes are expressed in the soybean seed coat. In conclusion, there is an intimate relationship between the I locus and the CHS multigene family leading to the control of CHS molecular expression and CHS enzyme activity which ultimately gives rise to variation in soybean seed coat pigmentation.
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