Involvement of fixLJ in the regulation of nitrogen fixation in Azorhizobium caulinodans

International audienceA gene bank of Azorhizobium caulinodans DNA constructed in the bacteriophage lambda GEM11 was screened with Rhizobium meliloti fixL and fixJ genes as probes. One positive recombinant phage, ORS lambda L, was isolated. The nucleotide sequence of a 3.7 kb fragment was established. Two open reading frames of 1512bp and 613bp were identified as fixL and fixJ. Kanamycin cartridges were inserted into the cloned fixL and fixJ genes and recombined into the host genome. The resulting mutants were Nif- Fix-, suggesting that the two genes were required for symbiotic nitrogen fixation and for nitrogen fixation in the free-living state. Using pnifH-lacZ and pnifA-lacZ fusions, it was shown that the FixLJ products controlled the expression of nifH and nifA in bacteria grown in the free-living state

Cleistogamia em Ruellia menthoides (Nees) Hiern e R. brevifolia (Pohl) C. Ezcurra (Acanthaceae) em fragmento florestal do Sudeste brasileiro

São abordados a morfologia e a biologia floral de Ruellia menthoides (Nees) Hiern e R. brevifolia (Pohl) C. Ezcurra, na Reserva Florestal Mata do Paraíso, remanescente de Floresta Atlântica, em Viçosa, Zona da Mata de Minas Gerais, Brasil. Ruellia menthoides e R. brevifolia são espécies cleistógamas, ou seja, apresentam dimorfismo floral, produzindo flores casmógamas normais (CA) e cleistógamas (CL). Além disso, formas intermediárias entre esses tipos florais (flores casmógamas reduzidas e semicleistógamas) também são observadas. Em R. menthoides a cleistogamia é inédita, ampliando o número de espécies desse gênero com esse mecanismo reprodutivo. A alogamia, nessas espécies, é favorecida pela produção de flores CA hercogâmicas, especialmente em R. menthoides, e pela dicogamia parcial. A floração de ambas as espécies ocorreu durante todo o ano. Houve pequena sobreposição do período de produção dos dois tipos florais em R. menthoides e ampla sobreposição em R. brevifolia. Em R. menthoides, o início da produção de flores CL coincidiu com o período de transição da estação úmida para a seca, e em R. brevifolia, a produção desse tipo floral ocorreu principalmente na estação seca. A complexidade taxonômica de Ruellia parece estar relacionada à escassez de informações sobre a biologia reprodutiva de suas espécies, que é agravada com o polimorfismo floral das espécies cleistógamas

Genetic variants associated with longitudinal changes in brain structure across the lifespan

Human brain structure changes throughout the lifespan. Brouwer et al. identified genetic variants that affect rates of brain growth and atrophy. The genes are linked to early brain development and neurodegeneration and suggest involvement of metabolic processes.Human brain structure changes throughout the lifespan. Altered brain growth or rates of decline are implicated in a vast range of psychiatric, developmental and neurodegenerative diseases. In this study, we identified common genetic variants that affect rates of brain growth or atrophy in what is, to our knowledge, the first genome-wide association meta-analysis of changes in brain morphology across the lifespan. Longitudinal magnetic resonance imaging data from 15,640 individuals were used to compute rates of change for 15 brain structures. The most robustly identified genes GPR139, DACH1 and APOE are associated with metabolic processes. We demonstrate global genetic overlap with depression, schizophrenia, cognitive functioning, insomnia, height, body mass index and smoking. Gene set findings implicate both early brain development and neurodegenerative processes in the rates of brain changes. Identifying variants involved in structural brain changes may help to determine biological pathways underlying optimal and dysfunctional brain development and aging.Stress-related psychiatric disorders across the life spa