Metarhizium robertsii is an entomopathogenic fungus that is additionally plant
rhizosphere competent. Two adhesin-encoding gens, Mad1 and Mad2, are involved in
insect pathogenesis or plant root colonization, respectively. This study examined
differential expression of the Mad genes for M robertsii grown on a variety of insectand plant-related substrates. Mad1 was up regulated in response to insect cuticles and
up regulation of Mad2 resulted from root exudates, tomato stems and non-preferred
carbohydrates. A time course analysis that compared water, minimal media, and
nutrient rich broth revealed Mad2 gene expression increased as nutrient availability
decreased. The regulation of Mad2 compared to known stress-related genes (Hsp30,
Hsp70 and ssgA) under various stresses (nutrient, pH, osmotic, oxidative, temperature)
revealed Mad2 to be generally up regulated by nutrient starvation only. Examination
of the Mad2 promoter region revealed two copies of a stress-response element (S TRE)
known to be regulated under the general stress response pathway
