Rab GTPases are the largest group of the small GTPases family, which play a pivotal role in the secretion of proteins. Arthrobotrys oligospora is a representative nematode-trapping fungus that can produce adhesive networks to capture nematodes. In this study, the roles of two Rab GTPases AoRab-7A and AoRab-2 were characterized by gene knockout in the fungus A. oligospora. The disruption of AoRab-7A hindered the mycelial growth in different media, the conidiation of ΔAoRab-7A transformants was almost abolished, and the transcription of four sporulation-related genes (AbaA, FluG, Hyp1, and VosA) was downregulated compared to the wild-type strain (WT). Furthermore, the tolerance of the ΔAoRab-7A mutants to sodium dodecyl sulfate (SDS) and HO was also significantly reduced compared to the WT, and the transcription of several genes related to environmental resistance, such as genes for catalase and trehalose synthase, was downregulated. Similarly, the extracellular proteolytic activity was decreased. Importantly, the ΔAoRab-7A mutants were unable to produce traps and capture nematodes. However, the disruption of gene AoRab-2 only affected the conidiation slightly but non-significantly, while other phenotypic traits were unaffected. Moreover, the gene AoRab-7A was also involved in the autophagy induced by nitrogen deprivation in A. oligospora. Our results revealed for the first time that the Rab GTPases are involved in the regulation of mycelial growth, conidiation, trap formation, stress resistance, and pathogenicity in the nematode-trapping fungus A. oligospora.
The discovery of low-cost, less toxic, and earth-abundant thermoelectric materials is a great challenge. Herein, with the aid of a unique and safe boron− chalcogen method, we discover the new tetragonal α-CsCu 5 Se 3 , featuring a previously unrecognized structure in the ternary family of Cs/Cu/Se. The structure is constructed by a Chinese-knot-like Cu 8 Se 8 building unit that is further linked into a 3D network. α-CsCu 5 Se 3 exhibits thermal stability that is superior to that of the recently established thermoelectric materials Cu 2−x Se and CsAg 5 Te 3 suffering unfavorable phase transitions. Distinct from the liquidlike migration in Cu 2−x Se, α-CsCu 5 Se 3 obeys a typical crystalline solid thermal transport behavior dominated by Umklapp scattering. In compariosn to the isostructural CsAg 5 Te 3 , α-CsCu 5 Se 3 shows a 30% volume decrease that leads to stronger orbital overlapping that markedly decreases the band effective mass (m*). With a smaller m* and a softer Cu−Se bond, α-CsCu 5 Se 3 eventually realizes a 200% increase in the power factor (8.17 μW/ (cm K 2 ), the highest among the copper-rich alkali-metal chalcogenides) and a figure of merit (ZT) of 1.03 at 980 K. Further, the doping in α-Cs(Cu 0.96 Sb 0.04 ) 5 Se 3 boosts the lattice anharmonicity by the lone pairs that, via intensifying the Umklapp scattering and slowing the phonon velocity, ensures a low lattice thermal conductivity (0.40 W/(m K)), and finally leads to a ZT max value of 1.30 at 980 K. Our discovery represents a step toward low-cost, earth-abundant, and high-performance chalcogenide materials that will shed useful light on future exploration in the related fields.
Cu2S, featuring low cost, nontoxicity, and earth abundance, has
been recently recognized as a high efficiency thermoelectric (TE)
material. However, before reaching the maximum of the figure of merit
(
ZT
), Cu2S undergoes three phase transformations
starting at 370 K, which give rise to severe problems, such as possible
decomposition and low reliability. Herein, we discover CsCu5S3 with phase transformation at 823 K, which is significantly
higher than the 370 K value of Cu2S. Single crystal diffraction
data reveal that its two phases are constructed by the same Cu4S4 columnar building unit via propagating either
at the opposite sides into a layered o-CsCu5S3, or at the four apexes into a 3D t-CsCu5S3, respectively. Interestingly, the o-to-t transformation is quick, but the
reverse one is relatively slow. Theoretical studies reveal that the
Cu4S4 column exhibits not only the most condensed
atomic aggregation (D
column) but also
the lightest effective mass (m*), along which higher
σ is realized. More interestingly, both phases exhibit remarkable ZT enhancements, 0.46 at 800 K for o-CsCu5S3, and 0.56 at 875 K for t-CsCu5S3, which are 170% and 175% that of Cu2S at the same temperature.
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