Evidence That MRas1 and MRas3 Proteins Are Associated with Distinct Cellular Functions during Growth and Morphogenesis in the Fungus Mucor racemosus

Threshold level of protein kinase A activity and polarized growth in Mucor rouxii

“…Thus, the poorer the culture medium, the slower the growth process and the earlier the threshold specific activity of PKA is attained. In accordance with these results, it has been recently reported that the levels of another family of proteins involved in signal transduction, the Ras proteins in Mucor racemosus, do not correlate with growth but with differentiation (Roze et al, 1999).…”

Comparison of Morphogenetic Networks of Filamentous Fungi and Yeast

“…Mras3 seems to be important at very early stages of spore germination, is degraded during the spherical growth phase, and upon its renewed synthesis might stimulate, together with Mras1, the initiation of polarized growth (Roze et al, 1999). In Mucor rouxii a dependence of cell size on the growth medium similar to that in S. cerevisiae has been observed: rich medium with glucose caused a delay of germ tube emergence and an increased size of the germ cell, whereas spore germination in medium containing maltose led to a shortened duration of the isotropic growth phase and a decreased diameter of the germ cells (Pereyra et al, 2000).…”

“…Pth11p is involved in host surface recognition and signals via the cAMP pathway since mutant phenotypes of pth11 strains, particularly concerning morphol-ogy and pathogenicitiy, could be suppressed by exogenous cAMP addition (DeZwaan et al, 1999). In Mucor racemosus different Ras proteins have been discovered, which play different roles during morphogenesis and polarized hyphal growth (Roze et al, 1999). The different G ␣ proteins and catalytic PKA subunits in U. maydis could be used to feed one core signaling cascade with inputs from different sources (Regenfelder et al, 1997;Dü rrenberger et al, 1998).…”

A novel Ras GTPase (Ras3) regulates conidiation, multi-stress tolerance and virulence by acting upstream of Hog1 signaling pathway in Beauveria bassiana

“…S1). As revealed in our analysis, Ras1 and Ras3 characterized previously in Mucor racemosus (Roze et al, 1999), indeed, fall in a distinct clade between the Ras1/A and Ras2/B clades of other filamentous fungi, and the documented Ras2 in this fungus is relatively closer to the Ras3-like homologs in other fungi. Ras3 in B. bassiana shares a sequence identity of 55-79% with the Ras3-like homologs found in nine filamentous fungi, including three other insect pathogens (Cordyceps militaris, Metarhizium acridum and Metarhizium robertsii separated from M. anisopliae).…”