Differential gene expression during aerobic germination of Mucor racemosus sporangiospores

Abstract

Evidence is provided suggesting that several modes of differential gene expression operate concomitantly during the first 60 min of germination of Mucor racemosus sporangiospores under air. Protein synthesis was initiated immediately upon exposure of the spores to nutrient medium and accelerated exponentially throughout the period of observation. All translation during the first 30 min of germination occurred using only preformed stable mRNAs as a template. Analysis of the protein products synthesized in vivo was performed by L-[35S]methionine labeling, one-and two-dimensional polyacrylamide gel electrophoresis, and autoradiography. The population of proteins accumulated during spore formation and present at the time of hlrvest differed significantly from those proteins synthesized during spore germination. Autoradiographs displayed several proteins synthesized during the former but not the latter morphogenetic process. Conversely, other proteins were synthesized during the first 30 min of germination but not during spore formation, even though the mRNA specifying these proteins must have been synthesized and stored in the dormant spore. A posttranscriptional regulatory mechanism that directs selective translation thus appears to exist in the developing spore. In addition, autoradiographs showed that many proteins, although made throughout the intervals examined, displayed significant changes in their relative rates of synthesis. One gene product exemplified a possible case of post-translational modification during the first hour of sporangiospore germination.

Effect of oxygen on morphogenesis and polypeptide expression by Mucor racemosus

“…The number and pattern of polypeptides detected in this study (about 400) is similar to that reported by Hiatt et al (4) anid Linz and Orlowski (6). In the former study, however, anaerobic (nitrogen-grown) yeasts were not examined, and these were a crucial part of this study as they allow a comparison of the polypeptides synthesized by these cells with those from aerobic mycelia, C02-grown yeasts, and most importantly, microaerobic mycelia.…”

“…1). In either anaerobic yeasts or microaerobic mycelia and in C02-grown yeasts polypeptides 4,5,6,10,13,14,18,20,22,23,25,27,28,29,32,34,36,41,49, and 52 were exclusively present or present in greater amounts in the oxygen-depleted cells (CO2 sparged, microaerobic or anaerobic) when compared with the aerobically grown cells. Thus, considerable qualitative and quantitative differences exist between O2-deprived cells and aerobic cells irrespective of the morphology of the cells.…”

Mucor dimorphism.

“…An analysis of the protein products synthesized in vivo during sporangiospore formation and germination was performed by radioisotopic labeling, 2-D PAGE, and autoradiography (132). It was found that the population of proteins accumulated during spore formation differ significantly from those proteins synthesized during spore germination.…”

Expression of a Gene Family in the Dimorphic Fungus Mucor racemosus Which Exhibits Striking Similarity to Human ras Genes

“…Though this finding suggests a role for MRAS3 in sporulation, it is also possible that MRAS3 functions during sporangiospore germination. Although previous studies suggest that a pool of mRNA is stored in sporangiospores and translated during germination (15)(16)(17), the MRAS3 gene may be transcribed and translated during sporulation, with the protein stored in sporangiospores and then activated during germination without de novo biosynthesis of MRAS3 protein. In M. mucedo and M. genevensis, spherical growth of sporangiospores at 1S 20C0 °2G\ ~5 30 .8< 2001 FIG.…”