Expression of three genes for elongation factor 1 alpha during morphogenesis of Mucor racemosus.

Three genes, TEF-1, -2, and -3, encode elongation factor 1 alpha in Mucor racemosus. Neutral and alkaline S1 nuclease analyses revealed that the genetic organization is unique for each of the genes. The number and size of the intervening sequences vary in these closely related genes, which suggests that complex genetic rearrangements gave rise to the elongation factor 1 alpha gene family. Nucleotide sequence data from restriction fragments isolated from the 5' and 3' ends of TEF-2 and -3 confirmed the presence of a second intervening sequence in these genes. These data along with S1 nuclease mapping revealed a region at the 3' end of the three genes which was predicted to be transcribed but untranslated. Unique oligonucleotides containing 19 bases were synthesized to hybridize to this unique trailer region in the elongation factor 1 alpha transcripts. These oligonucleotides were used as probes in standard Northern analysis of RNA purified from M. racemosus cells of several morphological types. It was determined that all three genes were expressed in the cell morphological types studied. However, the accumulated level of transcript derived from each gene varied considerably, with TEF-1 mRNA present in approximately twofold greater quantity than the TEF-3 transcript and up to sixfold greater quantity than TEF-2. The level of TEF-1 and -2 mRNA varied little among the cell morphological types studied, whereas TEF-3 mRNA was present in twofold greater quantity in sporangiospores than in either germlings or yeast cells which had been induced to undergo morphogenesis to hyphae. These data suggest that there is differential expression of the genes encoding elongation factor 1 alpha in M. racemosus. At least one gene, TEF-3, shows a morphology-specific pattern of transcript accumulation.