Neutral trehalases catalyse intracellular trehalose breakdown in the filamentous fungi Aspergillus nidulans and Neurospora crassa

A cAMP-activatable Ca2+-dependent neutral trehalase was identified in germi nating conidia of Aspergillus nidulans and Neurospora crassa. Using a PCR a pproach, A. nidulans and N. crassa genes encoding homologues of the neutral trehalases found in several yeasts were cloned and sequenced. Disruption o f the AntreB gene encoding A. nidulans neutral trehalase revealed that it i s responsible for intracellular trehalose mobilization at the onset of coni dial germination, and that this phenomenon is partially involved in the tra nsient accumulation of glycerol in the germinating conidia, Although trehal ose mobilization is not essential for the completion of spore germination a nd filamentous growth in A. nidulans, it is required to achieve wild-type g ermination rates under carbon limitation, suggesting that intracellular tre halose can partially contribute the energy requirements of spore germinatio n. Furthermore, it was shown that trehalose accumulation in A. nidulans can protect germinating conidia against an otherwise lethal heat shock. Becaus e transcription of the treB genes is not increased after a heat shock but i nduced upon heat shock recovery, it is proposed that, in filamentous fungi, mobilization of trehalose during the return to appropriate growth is promo ted by transcriptional and post-translational regulatory mechanisms, in par ticular cAMP-dependent protein kinase-mediated phosphorylation.