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The small hive beetle (SHB), Aethina tumida, has emerged as a worldwide threat to honey bees in the past two decades. These beetles harvest nest resources, feed on larval bees, and ultimately spoil nest resources with gelatinous slime together with the fungal symbiont Kodamaea ohmeri.

Here, we present the first chromosome-level genome assembly for the SHB. With a 99.1% representation of conserved (BUSCO) arthropod genes, this resource enables the study of chemosensory, digestive, and detoxification traits critical for SHB success and possible control. We use this annotated assembly to characterize features of SHB sex chromosomes and a female-skewed primary sex ratio. We also found chromosome fusion and a lower recombination rate in sex chromosomes than in autosomes.

Genome-enabled insights will clarify the traits that allowed this beetle to exploit hive resources successfully and will be critical for determining the causes of observed sex ratio asymmetries.

 

Cell division cycle 5 (Cdc5) is a highly conserved nucleic acid binding protein among eukaryotes and plays critical roles in development. Cdc5 can simultaneously bind to DNA and RNA by its N-terminal DNA-binding domain (DBD), but molecular mechanisms describing its nucleic acid recognition and the regulation of development through its nucleic acid binding remain unclear. Herein, we present a crystal structure of the N-terminal DBD of MoCdc5 (MoCdc5-DBD) from the rice blast fungus Magnaporthe oryzae. Residue K100 of MoCdc5 is on the periphery of a positively charged groove that is formed by K42, K45, R47, and N92 and is evolutionally conserved. Mutation of K100 significantly reduces the affinity of MoCdc5-DBD to a Cdc5-binding element but not to a conventional myeloblastosis (Myb) domain-binding element, suggesting that K100 is a key residue of the high binding affinity to Cdc5-binding element. Another conserved residue (R31) is located close to the U6 RNA in the structure of the spliceosome, and its mutation dramatically reduces the binding capacity of MoCdc5-DBD for U6 RNA. Importantly, mutations in these key residues, including R31, K42, and K100 in AtCDC5, an Arabidopsis thaliana ortholog of MoCdc5, greatly impair the functions of AtCDC5, resulting in pleiotropic development defects and reduced levels of primary microRNA transcripts. Taken together, our findings suggest that Cdc5-DBD binds nucleic acids with two distinct binding surfaces, one for DNA and another for RNA, which together contribute to establishing the regulation mechanism of Cdc5 on development through nucleic acid binding. 

Abstract. Parameterizations that impact wet removal of black carbon (BC)remain uncertain in global climate models. In this study, we enhance thedefault wet deposition scheme for BC in the Community Earth System Model (CESM)to (a) add relevant physical processes that were not resolved in thedefault model and (b) facilitate understanding of the relative importanceof various cloud processes on BC distributions. We find that the enhancedscheme greatly improves model performance against HIPPO observationsrelative to the default scheme. We find that convection scavenging, aerosolactivation, ice nucleation, evaporation of rain or snow, and below-cloudscavenging dominate wet deposition of BC. BC conversion rates for processesrelated to in-cloud water–ice conversion (i.e., riming, the Bergeronprocess, and evaporation of cloud water sedimentation) are relativelysmaller, but have large seasonal variations. We also conduct sensitivitysimulations that turn off each cloud process one at a time to quantify theinfluence of cloud processes on BC distributions and radiative forcing.Convective scavenging is found to have the largest impact onBC concentrations at mid-altitudes over the tropics and even globally. Inaddition, BC is sensitive to all cloud processes over the NorthernHemisphere at high latitudes. As for BC vertical distributions, convectivescavenging greatly influences BC fractions at different altitudes.Suppressing BC droplet activation in clouds mainly decreases the fraction ofcolumn BC below 5 km, whereas suppressing BC ice nucleation increases thatabove 10 km. During wintertime, the Bergeron process also significantlyincreases BC concentrations at lower altitudes over the Arctic. Oursimulation yields a global BC burden of 85 Gg; corresponding directradiative forcing (DRF) of BC estimated using the Parallel Offline RadiativeTransfer (PORT) is 0.13 W m−2, much lower than previous studies. Therange of DRF derived from sensitivity simulations is large, 0.09–0.33 W m−2,corresponding to BC burdens varying from 73 to 151 Gg. Due todifferences in BC vertical distributions among each sensitivity simulation,fractional changes in DRF (relative to the baseline simulation) are alwayshigher than fractional changes in BC burdens; this occurs because relocating BCin the vertical influences the radiative forcing per BC mass. Our resultshighlight the influences of cloud microphysical processes on BC concentrationsand radiative forcing.