Reduced activity of Arabidopsis thaliana HMT2, a methionine biosynthetic enzyme, increases seed methionine content.

In the S-methylmethionine cycle of plants, homocysteine methyltransferase (HMT) catalyzes the formation of two molecules of methionine from homocysteine and S-methylmethionine, and methionine methyltransferase (MMT) catalyzes the formation of methionine from S-methylmethionine using S-adenosylmethionine as a methyl group donor. Somewhat surprisingly, two independently isolated knockdown mutations of HMT2 (At3g63250), one of three Arabidopsis thaliana genes encoding homocysteine methyltransferase, increased free methionine abundance in seeds. Crosses and flower stalk grafting experiments demonstrate that the maternal genotype at the top of the flower stalk determines the seed S-methylmethionine and methionine phenotype of hmt2 mutants. Uptake, transport and inter-conversion of [(13)C]S-methylmethionine and [(13)C]methionine in hmt2, mmt and wild-type plants show that S-methylmethionine is a non-essential intermediate in the movement of methionine from vegetative tissue to the seeds. Together, these results support a model whereby elevated S-methylmethionine in hmt2 vegetative tissue is transported to seeds and either directly or indirectly results in the biosynthesis of additional methionine. Manipulation of the S-methylmethionine cycle may provide a new approach for improving the nutritional value of major grain crops such as rice, as methionine is a limiting essential amino acid for mammalian diets.

Ocorrência de protozoários intestinais em crianças do Ensino Fundamental de Sete Lagoas, Minas Gerais: um enfoque sobre a prevenção de enteroparasitoses / Occurrence of intestinal protozoa in children from elementary school in Sete Lagoas, Minas Gerais: a focus on the prevention of intestinal parasites

Objetivo: Estimar a prevalência de parasitos intestinais em alunos do Ensino Fundamental de Sete Lagoas, Minas Gerais, e instruí-los sobre medidas para prevenção de enteroparasitoses. Métodos: A análise coproparasitológica foi realizada pelo método de Lutz. Um questionário foi aplicado para obter informações sobre o conhecimento das crianças acerca dos parasitos intestinais antes e depois de uma intervenção educativa. Resultados: Foram analisadas amostras fecais de 83 crianças, sendo que 28 (33,7%) apresentaram cistos de protozoários: 27 (32,5%) continham protozoários comensais e apenas uma continha Giardia intestinalis (1,2%). Com relação aos hábitos de higiene, 81,4% das crianças afirmaram ingerir água filtrada; 75,4% lavavam as mãos antes de ingerir alimentos e 93,2% depois de ir ao banheiro; 86,5% afirmaram sempre lavar frutas e verduras antes de ingeri-las e apenas 21,2% tinham o hábito de andar sem calçados. Foi observado, ainda, que a intervenção educativa alcançou satisfatoriamente os objetivos propostos. Conclusão: Foi constatada uma baixa prevalência de parasitos na população avaliada, o que pode ser explicado, em parte, pelas medidas de higiene adotadas pela maioria das crianças. Contudo, a presença de amostras com protozoários comensais, também transmitidos pela via fecal-oral, reflete a necessidade de intervenções na área de saúde para prevenção de enteroparasitoses na região estudada

Objective: This work aimed to verify the prevalence of intestinal parasites in children from elementary school of Sete Lagoas, Minas Gerais, and instruct them about measures for preventing enteric parasitic diseases. Methods: Stool evaluation was performed using the Lutz method. A questionnaire was applied to children in order to obtain information about their knowledge concerning intestinal parasites, before and after a health education program. Results: We analyzed fecal samples from 83 students, and 28 (33.7%) had protozoa cysts: 27 (32.5%) samples contained commensal protozoa and only one child presented Giardia intestinalis (1.2%). Regarding hygiene habits, 81.4% of children reported drinking filtered water; 75.4% washed their hands before eating and 93.2% after using the toilet; 86.5% of them said washing before eating and only 21.2% had the habit of walking barefoot. It was also observed that the educational intervention successfully achieved the proposed objectives. Conclusion: There was a low prevalence of intestinal parasites in this population, which in part may be explained by hygiene measures adopted by most children. However, the presence of samples with commensal protozoa, which are also transmitted by the fecal-oral route, reflects the need for interventional education programs to prevent intestinal parasitic diseases in the studied region.

Application of a high-throughput HPLC-MS/MS assay to Arabidopsis mutant screening; evidence that threonine aldolase plays a role in seed nutritional quality.

Beyond their essential function as the building blocks of proteins, amino acids contribute to many aspects of plant biochemistry and physiology. Despite this, there are relatively large gaps in our understanding of the biochemical pathways and regulation of amino acid synthesis in plants. A rapid (1.5 min versus 20-90 min for standard methods) HPLC-MS/MS assay for separating 19 amino acids was developed for quantifying levels of free amino acids in plant tissue. This assay was used to determine the free amino acid content in the seeds of 10,000 randomly mutagenized Arabidopsis lines, and 322 Arabidopsis lines with increased levels of one or more amino acids were identified. The heritability of the mutant phenotype was confirmed for 43 lines with increased seed levels of the aspartate-derived amino acids Ile, Lys, Thr, or Met. Genetic mapping and DNA sequencing identified a mutation in an Arabidopsis threonine aldolase (AT1G08630, EC 4.1.2.5) as the cause of increased seed Thr levels in one mutant. The assay that was developed for this project has broad applicability to Arabidopsis and other plant species.