Plant-Type Trehalose Synthetic Pathway in Cryptosporidium and Some Other Apicomplexans

The trehalose synthetic pathway is present in bacteria, fungi, plants and invertebrate animals, but is absent in vertebrates. This disaccharide mainly functions as a stress protectant against desiccation, heat, cold and oxidation. Genes involved in trehalose synthesis have been observed in apicomplexan parasites, but little was known about these enzymes. Study on trehalose synthesis in apicomplexans would not only shed new light into the evolution of this pathway, but also provide data for exploring this pathway as novel drug target.We have observed the presence of the trehalose synthetic pathway in Cryptosporidium and other apicomplexans and alveolates. Two key enzymes (trehalose 6-phosphate synthase [T6PS; EC 2.4.1.15] and trehalose phosphatase [TPase; EC 3.1.3.12] are present as Class II bifunctional proteins (T6PS-TPase) in the majority of apicomplexans with the exception of Plasmodium species. The enzyme for synthesizing the precursor (UDP-glucose) is homologous to dual-substrate UDP-galactose/glucose pyrophosphorylases (UGGPases), rather than the "classic" UDP-glucose pyrophosphorylase (UGPase). Phylogenetic recontructions indicate that both T6PS-TPases and UGGPases in apicomplexans and other alveolates are evolutionarily affiliated with stramenopiles and plants. The expression level of T6PS-TPase in C. parvum is highly elevated in the late intracellular developmental stage prior to or during the production of oocysts, implying that trehalose may be important in oocysts as a protectant against environmental stresses. Finally, trehalose has been detected in C. parvum oocysts, thus confirming the trehalose synthetic activity in this parasite.A trehalose synthetic pathway is described in the majority of apicomplexan parasites including Cryptosporidium and the presence of trehalose was confirmed in the C. parvum oocyst. Key enzymes in the pathway (i.e., T6PS-TPase and UGGPase) are plant-type and absent in humans and animals, and may potentially serve as novel drug targets in the apicomplexans

Disruption of Yarrowia lipolytica TPS1 Gene Encoding Trehalose-6-P Synthase Does Not Affect Growth in Glucose but Impairs Growth at High Temperature

We have cloned the Yarrowia lipolytica TPS1 gene encoding trehalose-6-P synthase by complementation of the lack of growth in glucose of a Saccharomyces cerevisiae tps1 mutant. Disruption of YlTPS1 could only be achieved with a cassette placed in the 3′half of its coding region due to the overlap of its sequence with the promoter of the essential gene YlTFC1. The Yltps1 mutant grew in glucose although the Y. lipolytica hexokinase is extremely sensitive to inhibition by trehalose-6-P. The presence of a glucokinase, insensitive to trehalose-6-P, that constitutes about 80% of the glucose phosphorylating capacity during growth in glucose may account for the growth phenotype. Trehalose content was below 1 nmol/mg dry weight in Y. lipolytica, but it increased in strains expressing YlTPS1 under the control of the YlTEF1promoter or with a disruption of YALI0D15598 encoding a putative trehalase. mRNA levels of YlTPS1 were low and did not respond to thermal stresses, but that of YlTPS2 (YALI0D14476) and YlTPS3 (YALI0E31086) increased 4 and 6 times, repectively, by heat treatment. Disruption of YlTPS1 drastically slowed growth at 35°C. Homozygous Yltps1 diploids showed a decreased sporulation frequency that was ascribed to the low level of YALI0D20966 mRNA an homolog of the S. cerevisiae MCK1 which encodes a protein kinase that activates early meiotic gene expression

The Ume6 regulon coordinates metabolic and meiotic gene expression in yeast

The Ume6 transcription factor in yeast is known to both repress and activate expression of diverse genes during growth and meiotic development. To obtain a more complete profile of the functions regulated by this protein, microarray analysis was used to examine transcription in wild-type and ume6Δ diploids during vegetative growth in glucose and acetate. Two different genetic backgrounds (W303 and SK1) were examined to identify a core set of strain-independent Ume6-regulated genes. Among genes whose expression is controlled by Ume6 in both backgrounds, 82 contain homologies to the Ume6-binding site (URS1) and are expected to be directly regulated by Ume6. The vast majority of those whose functions are known participate in carbon/nitrogen metabolism and/or meiosis. Approximately half of the Ume6 direct targets are induced during meiosis, with most falling into the early meiotic expression class (cluster 4), and a smaller subset in the middle and later classes (clusters 5–7). Based on these data, we propose that Ume6 serves a unique role in diploid cells, coupling metabolic responses to nutritional cues with the initiation and progression of meiosis. Finally, expression patterns in the two genetic backgrounds suggest that SK1 is better adapted to respiration and W303 to fermentation, which may in part account for the more efficient and synchronous sporulation of SK1

Trehalose 6-phosphate is indispensable for carbohydrate utilization and growth in Arabidopsis thaliana

Genes for trehalose metabolism are widespread in higher plants. Insight into the physiological role of the trehalose pathway outside of resurrection plant species is lacking. To address this lack of insight, we express Escherichia coli genes for trehalose metabolism in Arabidopsis thaliana, which manipulates trehalose 6-phosphate (T6P) contents in the transgenic plants. Plants expressing otsA [encoding trehalose phosphate synthase (TPS)] accumulate T6P whereas those expressing either otsB [encoding trehalose phosphate phosphatase (TPP)] or treC [encoding trehalose phosphate hydrolase (TPH)] contain low levels of T6P. Expression of treF (encoding trehalase) yields plants with unaltered T6P content and a phenotype not distinguishable from wild type when grown on soil. The marked phenotype obtained of plants accumulating T6P is opposite to that of plants with low T6P levels obtained by expressing either TPP or TPH and consistent with a critical role for T6P in growth and development. Supplied sugar strongly inhibits growth of plants with reduced T6P content and leads to accumulation of respiratory intermediates. Remarkably, sugar improves growth of TPS expressors over wild type, a feat not previously accomplished by manipulation of metabolism. The data indicate that the T6P intermediate of the trehalose pathway controls carbohydrate utilization and thence growth via control of glycolysis in a manner analogous to that in yeast. Furthermore, embryolethal A. thaliana tps1 mutants are rescued by expression of E. coli TPS, but not by supply of trehalose, suggesting that T6P control over primary metabolism is indispensable for development

Relações entre atributos do solo e atividade de formigas em restingas Relationship among soil attributes and ant activity in restinga soils

Em solos de restinga de constituição areno-quartzosa aumenta a influência da fração orgânica e da atividade biológica em funções-chave dos solos, como a capacidade de reciclar e armazenar nutrientes. A análise de atributos do solo e da fauna edáfica em sítios sob diferentes coberturas vegetais é importante para entender o comportamento desses ambientes. Neste estudo, avaliaram-se atributos químicos, físicos e microbiológicos do solo e suas relações com a população de formigas de sítios de restinga sob diferentes coberturas vegetais no Estado de Sergipe. Foram coletadas amostras em seis coberturas vegetais (três sítios por cobertura), sendo quatro na área Caju (mata, capim-gengibre, coqueiral e capoeira) e duas na área Pirambu (mata de topo de duna e mata de sopé de duna). As análises químicas foram feitas em amostras coletadas nas camadas de 0-5 e 5-20 cm, e a atividade microbiana, avaliada por meio da hidrólise do diacetato de fluoresceína, foi determinada em amostras coletadas a 0-10 cm. A massa de fragmentos orgânicos foi avaliada em diferentes profundidades. Na avaliação das comunidades de formigas foram consideradas aquelas com atividade na superfície do solo. Na comparação entre os sítios foi utilizada a análise de componentes principais. Os atributos de compartimentos orgânicos (C orgânico, C orgânico dissolvido e fragmentos orgânicos) foram muito sensíveis à modificação da cobertura vegetal nos sítios do Caju, isolando os sítios sob mata dos alterados e os sítios sob capim-gengibre daqueles sob capoeira e coqueiral. Atributos da solução do solo influenciáveis pelo spray marinho (condutividade elétrica e concentração de K, Na e Mg) isolaram os sítios de Pirambu dos sítios do Caju. Os grupos de formiga mostraram elevado nível de especialização. A análise de correspondência canônica apontou baixa percentagem da variância da distribuição desses grupos e isolou os sítios de mata dos outros usos, indicando que existem outros atributos a serem considerados na distribuição.<br>In restinga soils with sand-quartzous constitution the influence of the organic fraction and biological activity on soil key functions is increased, e.g., the capacity of recycling and storing nutrients. The analysis of soil attributes and edaphic fauna at sites under different vegetation cover types is important to understand the behavior of these environments. In this study, chemical, physical and microbiological soil attributes of restinga sites and their relationships with ant populations under different vegetation types in the state of Sergipe were evaluated. Samples of six vegetation types (three sites per cover) were collected, four of which in the area of Caju (forest, ginger-grass, coconut palm plantation and brushwood) and two in the area of Pirambu (dune plateau forest and dune footslope forest). Chemical attributes were analyzed in samples collected from the layers 0-5 and 5-20 cm and the microbial activity evaluated by hydrolysis of fluorescein diacetate, in samples collected from the 0-10 cm layer. The organic fragment mass was evaluated at different depths. Ant communities with activity on the soil surface were considered for evaluation. The principal component analysis was used to compare the sites. The organic compartment attributes (organic C, dissolved organic C and organic fragments) were very sensitive to modifications in the vegetation cover at Caju sites, isolating the native forest sites from the disturbed ones and the ginger-grass site from the coconut palm and brushwood sites. Soil solution attributes influenced by sea-salt spray (electric conductivity, K, Na and Mg) distinguished the Pirambu from the Caju sites. The ant groups had a high level of specialization. Canonical correspondence analysis indicated a low percentage of variance of distribution of these groups and isolated the forest sites from other uses, indicating the existence of other attributes to be considered for distribution