cAMP and ras signalling independently control spore germination in the filamentous fungus Aspergillus nidulans
Fillinger S, Chaveroche MK, Shimizu K, Keller N, d’Enfert C
Date: 13 November 2005
The role of cAMP signalling during germination ofasexual spores (conidia) of the filamentous fungusAspergillus nidulans was investigated. A. nidulansstrains defective for adenylate cyclase (CyaA) or forthe functionally overlapping cAMP-dependent proteinkinase (PkaA) and newly characterized SchA proteinkinase, homologous to Saccharomyces cerevisiaeSch9, show altered trehalose mobilization andkinetics of germ tube outgrowth, in addition to otherdefects in colony formation. cAMP-dependent trehalosebreakdown is triggered by the addition of acarbon source independently of further catabolism,suggesting that cAMP signalling controls earlyevents of conidial germination in response to carbonsource sensing. Additional results suggest that cAMPhas targets other than PkaA and SchA and that PkaAretains activity in the absence of cAMP. Conversely,PkaA regulates cAMP levels in A. nidulans becausethese are elevated by Âª 250-fold in a strain that lacksPkaA. Furthermore, analysis of mutant strainsimpaired in both adenylate cyclase and RasA GTPasepreviously implicated in the control of A. nidulansspore germination suggested that RasA and cAMPsignalling proceed independently during germinationin A. nidulans.
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