Regulação da expressão gênica por oxigênio no fungo aquático Blastocladiella emersonii / Regulation of gene expression by oxygen in the aquatic fungus Blastocladiella emersonii

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In this work we analyzed global gene expression changes in the aquatic fungus Blastocladiella emersonii submitted to oxygen deprivation (hypoxia), using cDNA microarrays containing 3,773 distinct genes. In gradual hypoxia (gradual decrease in dissolved oxygen concentration, followed by reoxygenation) and direct hypoxia (direct decrease of dissolved oxygen concentration, followed by reoxygenation) we observed 650 differentially expressed genes in at least one of the stress conditions tested, 534 of them being affected (directly or indirectly) by oxygen availability, since they showed recovery of normal expression levels or a tendency to recover, when cells were reoxygenated. Besides modulating many genes with no previously assigned function, B. emersonii responds to hypoxia by readjusting the expression levels of genes responsible for energy production and consumption. At least transcriptionally, this fungus seems to favour anaerobic metabolism through the induction of genes encoding glycolytic enzymes and lactate dehydrogenase, while in the TCA-cycle, most genes were repressed or unchanged. Energy-costly processes like protein synthesis, amino acid metabolism, protein folding and transport had their gene expression profiles predominantly repressed during oxygen deprivation. Microarray experiments also showed similarities between the transcriptional profile of genes in hypoxia and iron (II) deprivation (treatment with the iron (II) chelator 2,2-dipyridyl), suggesting that these stresses are somehow related, giving good evidence that Fe2+ ion could have a role in the mechanism of oxygen sensing and/or response to hypoxia in B. emersonii. Furthermore, pretreatment of cells subjected to hypoxia with the antibiotic geldanamycin, a known inhibitor of the heat shock protein HSP90, caused a significant decrease in the induction of certain hypoxic genes, indicating that this fungus could have a mechanism similar to that of the mammalian hypoxia transcription factor HIF-1α, which is also affected by geldanamycin. Additionally, we developed an Agrobacterium tumefasciens-mediated protocol for transformation of B. emersonii that has shown to be promising. The capacity to transfer the T-DNA containing a hygromycin B resistance gene, present in the pBINPLUSHph binary vector, was evidenced by the normal growth and sporulation of the transformed cells in the presence of antibiotic and by amplification of the resistance gene from the genomic DNA of transformed cells

ASSUNTO(S)

cdna microarray microarranjos de cdna aquatic fungus fungo aquático hypoxia gene expression expressão gênica hipóxia

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