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E H Coe

Publications and source records attributed to E H Coe.

11 recordsLinked to original sources
PubMed1995

Allelic interactions heritably alter the activity of a metastable maize pl allele.

The maize pl locus encodes a transcriptional activator of anthocyanin biosynthetic genes. The Pl-Rhoades (Pl-Rh) allele confers robust purple anthocyanin pigment in several tissues. Spontaneous derivatives of Pl-Rh, termed Pl'-mahogany (Pl'-mah), arise that confer reduced pigment and are meiotically heritable. These derivatives influence other Pl-Rh alleles such that only Pl'-mah alleles are transmitted form a Pl-Rh/Pl'mah heterozygote. Genetic crosses establish that chromosomal segregation distortion does not explain this exclusive transmission and suggest that Pl-Rh invariably changes to Pl'-mah when exposed to Pl'-mah. Such behavior is a hallmark of paramutation. Cosegregation experiments demonstrate that this paramutagenic activity is genetically linked to the pl locus. By visually quantifying pl action through successive crosses, we find that phenotypic expression is inversely related to paramutation at two other maize loci, b and r. Previous analysis of b and r paramutation revealed extensive differences and led to suggestions of distinct molecular mechanisms. Consideration of the common features of all three systems reinvigorates the interpretation that the mechanistic processes of these three allelic interactions are similar.

Alleles↗
PubMed1993

Development of a core RFLP map in maize using an immortalized F2 population.

A map derived from restriction fragment length polymorphisms (RFLPs) in maize (Zea mays L.) is presented. The map was constructed in an immortalized Tx303 x CO159 F2 mapping population that allowed for an unlimited number of markers to be mapped and pooled F3 seed to be distributed to other laboratories. A total of 215 markers consisting of 159 genomic clones, 16 isozymes and 35 cloned genes of defined function have been placed on 10 chromosomes. An examination of segregation data has revealed several genomic regions with aberrant segregation ratios favoring either parent or the heterozygote. Mapping of cloned genes and isozymes that have been previously mapped by functional criteria has provided 29 points of alignment with the classical maize genetic map. Screening of all mapped RFLP probes against a collection of U.S. Corn Belt germplasm using EcoRI, HindIII and EcoRV has resulted in a set of 97 core markers being defined. The designation of a set of core markers allows the maize genome to be subdivided into a series of bins which serve as the backbone for maize genetic information and database boundaries. The merits and applications of core markers and bins are discussed.

Crosses, Genetic↗
PubMed1992

Molecular cloning and characterization of iojap (ij), a pattern striping gene of maize.

Iojap (ij) is a recessive striped mutant of maize affecting the development of plastids in a local and position-dependent manner on the leaves. The ij-affected plastids are transmitted to some of the progeny even when the function of the nuclear gene is restored. Developmental defects during embryogenesis and leaf proliferation are other phenotypic characteristics of ij. The extent of striping and the degree of developmental arrest in ij depend upon genetic background. To understand the diverse and unique phenotypic expression of ij, a transposon tagging experiment has been conducted using Robertson's Mutator (Mu). A new ij mutant was obtained from crosses of the reference allele of (ij-ref) to Mu lines. Subsequent genetic and molecular studies showed that the mutant carried a new ij allele (ij-mum1) from the Mu lines and contained a Mu1 element that cosegregated with the iojap phenotype. A 6.0 kb EcoRI genomic DNA fragment containing the Mu1 element was cloned. ij-ref is unstable, and revertants (Ij-Rev) have been obtained. Using the flanking DNA from the genomic clone as a probe, DNA polymorphisms were detected between ij-ref and these revertants. Further, transcripts were restored to the normal level in Ij-Rev seedlings. Comparison of genomic DNA clones from ij-ref, ij-mum1 and Ij indicated that the ij-ref allele contained 1.5 kb of additional DNA related to a transposable element, Ds. Germinal and somatic revertant alleles were derived by excision of this 1.5 kb element from ij-ref. The structure of the Ij gene and the DNA sequence of its transcribed region were determined. The Ij gene encodes a 24.8 kDa protein that showed no significant sequence similarity with proteins listed in databases.

Alleles↗
PubMed1986

Gene-dependent flavonoid 3'-hydroxylation in maize.

The influence of the gene Pr on flavonoid 3'-hydroxylase activity in maize is described. Specific activities are presented for the hydroxylase in seedlings and aleurone tissue homozygous dominant and recessive and heterozygous for Pr. Specific activity levels in both tissues increased in a nearly direct proportion with the increase in Pr dosage, which is consistent with Pr being the structural gene for the hydroxylase. Regression analysis of the gene dosage:enzyme activity comparison yielded correlation coefficients of 0.979 and 0.959 for the seedlings and aleurone, respectively. Quantitative identification of the cyanidin and pelargonidin in the aleurone indicated that cyanidin increased with an increase in dominant Pr, while pelargonidin decreased, although the increases and decreases observed were not directly proportional to the gene dosage. Comparison of the cyanidin/pelargonidin ratio to the gene dosage ratio in the different tissues showed a strong correlation (0.998), which demonstrates that the dosage of Pr controls the ratio of cyanidin to pelargonidin. Cyanidin was found at a low concentration in aleurone homozygous for pr. Hydroxylase activity in maturing field plants reaches its peak concentration near anthesis and is present at an appreciable concentration in mature plant tissue homozygous for pr, as well as in seedlings homozygous for pr. Suggestion is made that pr could be a hypomorphic allele or that a duplicate gene for Pr could exist to account for the hydroxylase activity in homozygous pr tissue. Evidence for the hydroxylase in the aleurone and the seedlings and the pigment ratio data from the aleurone suggest that Pr is indeed a structural gene for NADPH:flavonoid 3'-hydroxylase.

Cytochrome P-450 Enzyme System↗
PubMed1984

Influence of B and Pl on UDPG:Flavonoid-3-O-glucosyltransferase in Zea mays L.

The influence of the genetic constitution at the B and Pl loci on UDPG:flavonoid-3-O-glucosyltransferase activity is described. More than a 90% reduction in activity is found when either B or Pl was present in the homozygous recessive condition. A positive correlation between quercetin-3-O-glucoside and pelargonidin-3-O-glucoside production is observed for all genotypes tested. Changes in UFGT activity during plant development are described for R-r B Pl plants.

Anthocyanins↗
PubMed1983

Clonal analysis of corn plant development. I. The development of the tassel and the ear shoot.

The development of the tassel and the ear shoot has been investigated in corn (Zea mays L.). X irradiation of dry kernels and seedlings heterozygous for anthocyanin markers or for factors altering tassel and ear morphology results in the formation of clones (sectors) from cells of the apical meristem. Most tassels develop from 4 +/- 1 cells of the mature embryo. The expression of ramosa-1, tunicate, tassel seed-6, and vestigial is cell autonomous in the tassel. These genes act late in development and modify the developmental fate or decision of an individual clone and not of the whole group of cells producing a tassel. The ear shoot develops from lineages of one to three cells derived each from the L-I (outmost cell layer) and L-II (second cell layer) of the apical meristem. Typically the clones start in the ear shoot (in the husks and possibly in the cob), extend upward in an internode, continue along the margin of the leaf sheath or leaf blade at the node above, and terminate in this or the next higher leaf. The separation of lineages for ear shoot and internode occurs in the period around 13 days after sowing. The analysis of clonal boundaries shows that a small number of embryonic cells become isolated in their developmental capacity. This commitment process appears to be analogous to the process of compartmentation in the imaginal disks of fruit flies. The extent of proliferation of individual cells within a group of highly flexible and any particular clone does not generate a specific part of a tassel or an ear shoot. There must be cellular communication between various clones so that the overall size and morphology of an organ remain normal and more or less fixed. Thus the process of development in plants is also highly regulative in nature and shares many features in common with development in fruit flies.

Anthocyanins↗
PubMed1977

Control of anthocyanin synthesis by the C locus in maize.

Alleles at the C locus in maize include C, one of the complementary genes required for anthocyanin pigmentation in the aleurone tissue of the mature kernel; C-I, dominant inhibitor of pigmentation; and c, recessive colorless. The recessive colorless alleles can be differentiated into two distinct forms: c-p (p for positive), conditional colored, develops pigment in the light during germination; c-n (n for negative), colorless, fails to develop pigment at any time. Four-point linkage data support the differentiation of c-p (in the alleles derived from either W22 or K55 inbreds) from c-n. Light and germination conditions are both required for anthocyanin synthesis in c-p tissue, but light "induction" and germination "induction" are two separable events inasmuch as the light stimulus can be stored. The ratio between the two major pigments, cyanidin and pelargonidin, is lowered in c-p tissue relative to that in dominant colored (C) tissue for the W22 allele and background but not for the K55 allele and background. Segregation tests reveal that the difference in the cyanidin-to-pelargonidin ratio in the C and the c-p tissue of W22 background is associated with the C locus. Several properties of the C locus, including anomalous allelic functions, stage- and properties of the C locus, including anomalous allelic functions, stage- and condition-dependent anthocyanin synthesis controlled by its multiple allelic series, and tissue-specific function, suggest that C may be a regulatory locus in the control of anthocyanin synthesis in aleurone tissue.

Alleles↗
PubMed1977

Gene-dependent flavonoid glucosyltransferase in maize.

A direct relationship between a specific gene and a specific enzyme involved in flavonoid biosynthesis is reported for the gene Bz and uridine diphosphoglucose: quercetin glucosyltransferase in maize pollin, seedlings, and seeds. Ratios are presented for specific activities of the glucosyltransferase from pollen, seed, and seedling tissues homozygous and heterozygous for Bz and homozygous for bz.

Flavonoids↗