RESUMO
The cloned y1 locus of maize was sequenced and found to encode phytoene synthase. Different "wild-type" alleles of the locus were found to differ by the insertion of transposable elements in their promoter and polyA addition regions, and by the length of a CCA tandem repeat series, without any obvious effect on function of the gene. A dominant Y1 ("wild-type") allele was observed to be expressed at highest levels in the seedling but also in the embryo and endosperm. The Mu3 transposable element insertion responsible for a pastel allele of y1, which gives lowered levels of carotenoids in the endosperm of kernels and seedlings grown at high temperatures, was located in the 5' end of the gene. Although the size of the transcript from this y1 mutation suggests that the Mu3 element provides the promoter for this allele, leaf tissue in this mutant line contained approximately normal amounts of y1 mRNA. A recessive allele of y1, which conditions normal levels of carotenoids in the embryo and seedling, but almost no carotenoids in the endosperm, was found to accumulate normal amounts of y1 mRNA in the seedling and embryo, while y1 transcripts were not detected in the endosperm.
Assuntos
Alquil e Aril Transferases , Genes de Plantas , Transferases/genética , Zea mays/enzimologia , Zea mays/genética , Alelos , Sequência de Aminoácidos , Sequência de Bases , Carotenoides/análise , Carotenoides/biossíntese , Clonagem Molecular , Primers do DNA , Elementos de DNA Transponíveis , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Geranil-Geranildifosfato Geranil-Geraniltransferase , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Regiões Promotoras Genéticas , Proteínas Recombinantes/biossíntese , Sementes , Homologia de Sequência de Aminoácidos , Transferases/biossíntese , Repetições de TrinucleotídeosRESUMO
Lymphoepithelioma-like carcinomas have been reported outside the nasopharynx in many sites, including the uterine cervix. The association with the Epstein-Barr virus in the latter site is still controversial. To date, Epstein-Barr virus genome has only been demonstrated in Asian patients. We report a case of lymphoepithelioma-like carcinoma of the uterine cervix in a white woman in whom the Epstein-Barr virus infection was tested for by in situ hybridization and polymerase chain reaction. The results of both techniques were negative. Our case and a review of the literature support the contention that cervical lymphoepithelioma-like carcinoma is not associated with Epstein-Barr virus infection in non-Asian patients.