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Allelic Series (allelic + series)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Mutations in the cinnamate 4-hydroxylase gene impact metabolism, growth and development in Arabidopsis

THE PLANT JOURNAL, Issue 5 2009
Anthony L. Schilmiller
Summary The initial reactions of the phenylpropanoid pathway convert phenylalanine to p -coumaroyl CoA, a branch point metabolite from which many phenylpropanoids are made. Although the second enzyme of this pathway, cinnamic acid 4-hydroxylase (C4H), is well characterized, a mutant for the gene encoding this enzyme has not yet, to our knowledge, been identified, presumably because knock-out mutations in this gene would have severe phenotypes. This work describes the characterization of an allelic series of Arabidopsis reduced epidermal fluorescence 3 (ref3) mutants, each of which harbor mis-sense mutations in C4H (At2g30490). Heterologous expression of the mutant proteins in Escherichia coli yields enzymes that exhibit P420 spectra, indicative of mis-folded proteins, or have limited ability to bind substrate, indicating that the mutations we have identified affect protein stability and/or enzyme function. In agreement with the early position of C4H in phenylpropanoid metabolism, ref3 mutant plants accumulate decreased levels of several different classes of phenylpropanoid end-products, and exhibit reduced lignin deposition and altered lignin monomer content. Furthermore, these plants accumulate a novel hydroxycinnamic ester, cinnamoylmalate, which is not found in the wild type. The decreased C4H activity in ref3 also causes pleiotropic phenotypes, including dwarfism, male sterility and the development of swellings at branch junctions. Together, these observations indicate that C4H function is critical to the normal biochemistry and development of Arabidopsis. [source]

A tomato mutant that shows stunting, wilting, progressive necrosis and constitutive expression of defence genes contains a recombinant Hcr9 gene encoding an autoactive protein

THE PLANT JOURNAL, Issue 3 2006
Claire L. Barker
Summary The tomato Cf-9 gene confers resistance to races of the leaf mould fungus Cladosporium fulvum that carry the Avr9 avirulence gene. Cf-9 resides at a locus containing five paralogous genes and was isolated by transposon tagging using a modified maize Dissociation (Ds) element. The tagging experiment generated an allelic series of Ds -induced mutations of Cf-9, most of which were wild type in appearance. However, one mutant, designated M205, showed stunted growth, wilting, progressive leaf chlorosis and necrosis and constitutive expression of defence genes. The phenotype of M205 was caused by a semidominant, Avr9 -independent mutation that co-segregated with a Ds element insertion at the Cf-9 locus. Molecular genetic analysis indicated that the Cf-9 locus of M205 had undergone recombination, generating a chimeric gene, designated Hcr9-M205, that comprised an in-frame fusion between the 5, coding region of the Cf-9 paralogue, Hcr9-9A, and the 3, coding region of Cf-9. The presence of a possible excision footprint adjacent to the junction between Hcr9-9A and Cf-9, and a Ds insertion at the homologous position in the downstream paralogue Hcr9-9D, is consistent with recombination between Hcr9-9A and Cf-9 promoted by transposition of Ds from Cf-9 into Hcr9-9D. Agrobacterium tumefaciens -mediated transient expression of Hcr9-M205 in Nicotiana tabacum caused chlorosis and the accumulation of defence gene transcripts, indicating that the protein encoded by this novel Hcr9 gene is autoactive. [source]

Genetic heterogeneity at the bovine KIT gene in cattle breeds carrying different putative alleles at the spotting locus

ANIMAL GENETICS, Issue 3 2010
L. Fontanesi
Summary According to classical genetic studies, piebaldism in cattle is largely influenced by the allelic series at the spotting locus (S), which includes the SH (Hereford pattern), S+ (non-spotted) and s (spotted) alleles. The S locus was mapped on bovine chromosome 6 in the region containing the KIT gene. We investigated the KIT gene, analysing its variability and haplotype distribution in cattle of three breeds (Angus, Hereford and Holstein) with different putative alleles (S+, SH and s respectively) at the S locus. Resequencing of a whole of 0.485 Mb revealed 111 polymorphisms. The global nucleotide diversity was 0.087%. Tajima's D- values were negative for all breeds, indicating putative directional selection. Of the 28 inferred haplotypes, only five were observed in the Hereford breed, in which one was the most frequent. Coalescent simulation showed that it is highly unlikely (P < 10E-6) to obtain this low number of haplotypes conditionally on the observed number of segregating SNPs. Therefore, the neutral model could be rejected for the Hereford breed, suggesting that a selection sweep occurred at the KIT locus. Twelve haplotypes were inferred in Holstein and Angus. For these two breeds, the neutral model could not be rejected. High heterogeneity of the KIT gene was confirmed from a phylogenetic analysis. Our results suggest a role of the KIT gene in determining the SH allele(s) in the Hereford, but no evidence of selective sweep was obtained in Holstein, suggesting that complex mechanisms (or other genes) might be the cause of the spotted phenotype in this breed. [source]

Multiple cutaneous and uterine leiomyomata resulting from missense mutations in the fumarate hydratase gene

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 1 2006
G. S. Chuang
Summary Multiple cutaneous and uterine leiomyomata (MCL) is an autosomal dominant disorder characterized by the development of benign smooth muscle tumours (leiomyomas) in the skin and uterus of affected women, and in the skin of affected men. In rare cases, MCL has been associated with a predisposition to the rare type II papillary renal cell cancer, also known as hereditary leiomyomatosis and renal cell cancer. The genetic locus for MCL has been mapped to chromosome 1q42.3,43 and subsequently, germline mutations in the fumarate hydratase (FH) gene have been identified. In addition, analysis of FH in some tumours of MCL patients revealed a second mutation inactivating the wild-type allele, suggesting that FH may function as a tumour suppressor gene. Here, we report two cases of MCL patients with FH mutations, designated as T287P and R190L. T287P represents a novel mutation of a highly conserved amino acid of the FH protein. In addition, a patient with an unusual clinical presentation of MCL was found to have the recurrent mutation, R190L, raising the possibility of incorporating FH sequencing as a diagnostic tool. Our findings extend the allelic series of mutations in FH and support its status as the underlying cause of MCL. [source]