GUP1 and its close homologue GUP2, encoding multi-membrane-spanning proteins involved in active glycerol uptake in Saccharomyces cerevisiae

Many yeast species can utilise glycerol, both as sole carbon source and as an osmolyte. In Saccharomyces cerevisiae, physiological studies have previously shown the presence of an active uptake system driven by electrogenic proton symport. We have used transposon mutagenesis to isolate mutants affected in the transport of glycerol into the cell. Here we present the identification of YGL084c, encoding a multi-membrane-spanning protein, as being essential for proton symport of glycerol into Saccharomyces cerevisiae. The gene is named GUP1 (Glycerol UPtake) and is important for growth on glycerol as carbon and energy source, as well as for osmotic protection by added glycerol, of a strain deficient in glycerol production. Another ORF, YPL189w, presenting a high degree of homology to YGL084c, similarly appears to be involved in active glycerol uptake in salt-containing glucose-based media in strains deficient in glycerol production. Analogously, this gene is named GUP2. To our knowledge, this is the first report on a gene product involved in active transport of glycerol in yeasts. Mutations with the same phenotypes occurred in two other open reading frames of previously unknown function, YDL074c and YPL180w.Comunidade Europeia (CE) - contract BIO4-CT95-0161

Combining ability of maize inbred lines evaluated in three environments in Brazil Capacidade de combinação de linhagens de milho avaliadas em três ambientes do Brasil

For tropical areas like Brazil, genotype x environment interaction is an important source of variation. Our objectives were to examine the combining abilities and their interaction with environments in ten selected maize (Zea mays L.) inbred lines in diallel crosses and to identify candidates for promising hybrid combinations. Crosses and checks were evaluated through a 7 x 7 triple lattice design at three locations during the 1984/85 season. Several agronomic traits were evaluated, but here only data on ear yield are discussed. Yield data were adjusted for stand variation (correction to 50 plants per plot) and grain moisture (15.5%). Data for ear yield were analysed using an adaptation of Griffing’s method IV for complete diallel crosses, and experiments were repeated in several environments. The means of the crosses over all environments ranged from 6.6 t/ha to 10.3 t/ha. The combining ability analysis of diallel data across environments showed highly significant (P<0.01) effects for environment, general combining ability (GCA), specific combining ability (SCA), and GCA x environment interaction. The SCA x environment interaction was not significant. Results showed that both GCA and SCA were important for this diallel cross. Considering the 13 hybrids that showed higher yields than the commercial hybrid controls, contributions by GCA and SCA effects were 56% and 44%, respectively. On the other hand, selecting only the best five hybrids, SCA effects were always more important than GCA effects for each environment and over all environments.<br>Em regiões tropicais a interação genótipo x ambiente é uma importante fonte de variação. Esse estudo teve por objetivos avaliar em cruzamentos dialélicos as capacidades de combinação e suas interações com ambientes e identificar as combinações híbridas mais promissoras entre dez linhagens selecionadas de milho (Zea mays L.). Os híbridos e as testemunhas foram avaliados no delineamento látice triplo 7 x 7 em três ambientes durante o ano agrícola de 1984/85. Nesse trabalho são discutidos apenas os dados de produção de grãos, os quais foram corrigidos para a variação de estande (50 plantas por parcela) e umidade de grão (15,5%). Os dados de peso de espigas foram analisados utilizando-se uma adaptação do método IV de Griffing, no qual os cruzamentos obtidos no dialélico completo são avaliados em vários ambientes. A média dos híbridos considerando todos os ambientes variou de 6,6 t/ha a 10,3 t/ha. Na análise dialélica conjunta foram detectadas diferenças altamente significativas (P<0,01) para ambientes, capacidade geral de combinação (CGC), capacidade específica de combinação (CEC) e para a interação CGC x ambientes; a interação CEC x ambientes não foi significativa. Os resultados obtidos mostraram que tanto CGC como CEC foram importantes para esse conjunto de híbridos. Para os 13 híbridos mais produtivos as contribuições dos efeitos da CGC e CEC foram 56% e 44%, respectivamente. Por outro lado, tomando-se apenas os cinco melhores híbridos, os efeitos da CEC foram sempre mais expressivos em relação aos efeitos da CGC, para cada híbrido e na média dos ambientes