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ABSTRACT The rise of drug resistance in fungal pathogens is becoming a serious problem owing to the limited number of antifungal drugs available. Identifying and targeting factors essential for virulence or development unique to fungal pathogens is one approach to develop novel treatments for fungal infections. In this study, we present the identification and functional characterization of a novel developmental regulator in Aspergillus fumigatus, AfMed15, which contained a conserved Med15_fungal domain, as determined by screening of a mutant library that contained more than 2,000 hygromycin-resistant A. fumigatus transformants. Downregulating the expression of Afmed15 abolished the conidiation and decreased the fungal virulence in an insect model. Strikingly, the overexpression of Afmed15 caused fungal death accompanied by intensive autophagy. RNA sequencing of an Afmed15 overexpression strain revealed that altered gene expression patterns were associated with carbon metabolism, energy metabolism, and translation. Interestingly, the addition of metal ions could partially rescue fungal death caused by the overexpression of Afmed15, indicating that disordered ion homeostasis is a potential reason for the fungal death caused by the overexpression of Afmed15. Considering that the precise expression of Afmed15 is crucial for fungal development, virulence, and survival and that no ortholog was found in humans, Afmed15 is an ideal target for antifungal-drug development. IMPORTANCE The identification and characterization of regulators essential for virulence or development constitute one approach for antifungal drug development. In this study, we screened and functionally characterized Afmed15, a novel developmental regulator in A. fumigatus. We demonstrate that the precise transcriptional expression of Afmed15 is crucial for fungal asexual development, virulence, and survival. Downregulating the expression of Afmed15 abolished the conidiation and decreased the fungal virulence in an insect model. In contrast, the overexpression of Afmed15 caused fungal death accompanied by intensive autophagy. Our study provides a foundation for further studies to identify compounds perturbing the expression of Afmed15 that may be used for the prevention of invasive A. fumigatus infections.

Cytokinesis, as the final step of cell division, plays an important role in fungal growth and proliferation. In the filamentous fungus Aspergillus nidulans, defective cytokinesis is able to induce abnormal multinuclear or nonnucleated cells and then result in reduced hyphal growth and abolished sporulation. Previous studies have reported that a conserved contractile actin ring (CAR) protein complex and the septation initiation network (SIN) signaling kinase cascade are required for cytokinesis and septation; however, little is known about the role(s) of scaffold proteins involved in these two important cellular processes. In this study, we show that a septumlocalized scaffold protein paxillin B (PaxB) is essential for cytokinesis/septation in A. nidulans. The septation defects observed in a paxB deletion strain resemble those caused by the absence of another identified scaffold protein, a-actinin (AcnA). Deletion of a-actinin (AcnA) leads to undetectable PaxB at the septation site, whereas deletion of paxB does not affect the localization of a-actinin at septa. However, deletion of either a-actinin (acnA) or paxB causes the actin ring to disappear at septation sites during cytokinesis. Notably, overexpression of a-actinin acnA partially rescues the septum defects of the paxB mutant but not vice versa, suggesting AcnA may play a dominant role over that of PaxB for cytokinesis and septation. In addition, PaxB and a-actinin affect the septal dynamic localization of MobA, a conserved component of the SIN pathway, suggesting they may affect the SIN protein complex function at septa. Protein pulldown assays combined with liquid chromatography-mass spectrometry identification indicate that a-actinin AcnA and PaxB likely do not directly interact, but presumably belong to an actin cytoskeleton protein network that is required for the assembly and contraction of the CAR. Taken together, findings in this study provide novel insights into the roles of conserved scaffold proteins during fungal septation in A. nidulans. [ABSTRACT FROM AUTHOR]

GeV-class proton beam with an average power of several megawatts has many important applications in particle physics towards the intensity frontier, as well as in the advanced energy and material science. There are three different types of constructed accelerators for high power proton beam production: The cyclotron, linear accelerator and rapid-cycling synchrotron. The highest beam power of these accelerators currently is 1.4 MW. Studies have shown that the energy efficiency of the PSI cyclotron is about two times of the other types. Thus, the isochronous accelerator is a good technical route to develop proton machines with high beam power and high power efficiency. The isochronous fixed-field alternating gradient accelerators (FFAGs) scheme is a promising candidate for next-generation GeV-class high power proton driver. There are two bottle-neck problems in the development of GeV/mA class FFAG: As an isochronous accelerator, radial tune of isochronous FFAG is approximately increasing with beam energy in a linear way, and thus the integer resonance crossing problem becomes an inevitable problem. Single turn extraction with very low beam losses is also a verry important issue of high power isochronous FFAG. To the author’s knowledge, high beam extraction efficiency for beam energy of GeV-class is still unresolved. To solve those problems, an idea of integer resonance suppressor (IRS) which intentionally introduces the third harmonic magnetic field was proposed. One IRS is made up of two pair of coils, and each pair has independent power supply to generate the required harmonic magnetic bump. IRS can not only inhibit the radial oscillation and beam size blowup caused by integer resonance crossing but also contribute to a controllable coherent oscillation which is helpful to beam extraction with high efficiency. In the CYCIAE-FFAG design, νr=3 resonance is the lowest order resonance. Third harmonic field of only 1 Gs (1 Gs=10-4 T) can drive large coherent oscillation and then the following intrinsic resonance 3νr=10 will lead to serious beam size blowup effect. However, IRS can compensate the driving error and minimize the coherent oscillation before reaching the detrimental resonance. IRS provides a possibility of relaxing the requirement of magnet manufacture and installation. Our simulations show that third harmonic field of 10 Gs is acceptable with proper IRS settings. In the PSI 590 MeV ring cyclotron, beam is eccentrically injected to give rise to coherent oscillation. However, in CIAE-FFAG design, the beam was injected centrally and controllable amplitude of coherent oscillation was introduced in the integer resonance crossing process. The IRS scheme makes it possible to have knobs to adjust the amplitude and phase of coherent oscillation, which will be much easier to enlarge the turn separation. Taking the CYCIAE-FFAG project for example, simulations in this paper show that IRS can not only reduce the beam size growth rate to less than 5%, but also enlarge the turn separation to 3 cm. That is to say, IRS not only acts as resonance suppressor, but also plays the role of separation optimizer between the last and second last turn. The result shows that IRS is a potential solution for resonance crossing and extraction problems of GeV/mA class circular accelerator.