We found that 2 week old conidia of ΔtppB were more susceptible to heat shock than wild-type conidia, indicating that trehalose protects the spores from thermal stress. These results are in line with earlier see more studies in Aspergillus

species [11, 12, 23]. However, in contrast to results from A. fumigatus and A. nidulans, we could not detect any increased sensitivity of ΔtppB to oxidative stress [11, 12], salt or acid stress, or any decreased viability after long term storage. It should be noted that unlike ΔtppB in our experiments, which harbored approximately one third of wild-type trehalose content, the A. fumigatus and A. nidulans mutants were totally depleted of trehalose. In S. cerevisiae it has been shown that, MM-102 nmr using a two-hybrid assay, the four homologous proteins physically interact. When repeating the experiments using the six identified A. niger proteins, we could observe interactions for four of six proteins. These results suggest that TppA and TpsA-C form a complex, while the phylogenetically more distant proteins, TppB and TppC, are present outside the complex. However, due to the experimental limits, it is possible that neither TppB nor TppC was correctly folded and therefore not interacting. It is notable that in S. cerevisiae, a truncated version of Tsl1 was necessary for the success of the interaction experiments [40], in contrast to our experiment in which

we only used full-length proteins. Conclusions

To conclude, in this study novel information about the six gene products involved in trehalose synthesis in A. niger has been generated. When characterizing deletion mutants, lack of the most conserved trehalose phosphate synthase tpsA, the trehalose phosphate phosphatase tppA, or the previously non-characterized tppB, resulted in lower trehalose contents. An additional insight is that the components in a putative trehalose synthesis complex differ among the Aspergilli, but some gene products are common throughout the fungal Dichloromethane dehalogenase check details kingdom. Acknowledgements Dr. Jonathan Hilmer for assistance with the T6P analysis and Dr. Su-lin Leong for proofreading the manuscript before submission, are greatly acknowledged. This work was financed by the Swedish research council Formas. References 1. Avonce N, Mendoza-Vargas A, Morett E, Iturriaga G: Insights on the evolution of trehalose biosynthesis. BMC Evol Biol 2006, 6:109.PubMedCentralPubMedCrossRef 2. Iordachescu M, Imai R: Trehalose biosynthesis in response to abiotic stresses. J Integr Plant Biol 2008,50(10):1223–1229.PubMedCrossRef 3. Elbein AD, Pan YT, Pastuszak I, Carroll D: New insights on trehalose: a multifunctional molecule. Glycobiology 2003,13(4):17R-27R.PubMedCrossRef 4. Thevelein JM: Regulation of trehalose mobilization in fungi. Microbiol Mol Biol Rev 1984,48(1):42–59. 5. Elbein AD: The metabolism of α, α-trehalose. Adv Carbohydr Chem Biochem 1974, 30:227–256.PubMedCrossRef 6.