A new species of Nidirana from the N. pleuraden group (Anura, Ranidae) from western Yunnan, China

The Music Frog genus Nidirana was recently resurrected as a distinct genus and contains 14 species distributed in subtropical eastern and southeastern Asia. The species diversity of Nidirana is dramatically underestimated, and half of its species was described in the last five years. In this study, Nidirana occidentalis sp. nov., a new species of Music Frog from western Yunnan, China, is proposed based on morphological and molecular evidences. The new species was previously misidentified as N. pleuraden, but can be distinguished from the true N. pleuraden from eastern Yunnan, and all other congeners, by a combination of morphological characteristics, and significant divergence in the mitochondrial genes (≥ 5.1% in 16S and ≥ 8.9% in CO1). Nidirana occidentalis sp. nov. is assigned to the N. pleuraden group on the basis of morphological characters, but its phylogenetic placement remains unresolved due to weak branch support. Geographically, these two species are isolated by the Red River in Yunnan, supporting the hypothesis that the Red River is an important geographical barrier that drives speciation in flora and fauna. Nidirana occidentalis sp. nov. represents the second species of N. pleuraden group and the 15th species of the genus.

Isoform-specific characterization implicates alternative splicing in APOBEC3B as a mechanism restricting APOBEC-mediated mutagenesis

ABSTRACTAPOBEC3A (A3A) and APOBEC3B (A3B) enzymes drive APOBEC-mediated mutagenesis, but the understanding of the regulation of their mutagenic activity remains limited. Here, we showed that mutagenic and non-mutagenic A3A and A3B enzymes are produced by canonical and alternatively spliced A3A and A3B isoforms, respectively. Notably, increased expression of the canonical A3B isoform, which encodes the mutagenic A3B enzyme, predicted shorter progression-free survival of bladder cancer patients. Expression of the mutagenic A3B isoform was reduced by exon 5 skipping, generating a non-mutagenic A3B isoform. The exon 5 skipping, which was dependent on the interaction between SF3B1 splicing factor and weak branch point sites in intron 4, could be enhanced by an SF3B1 inhibitor, decreasing the production of the mutagenic A3B enzyme. Thus, our results underscore the role of A3B, especially in bladder cancer, and implicate alternative splicing of A3B as a mechanism and therapeutic target to restrict APOBEC-mediated mutagenesis.

Subcritical convection of liquid metals in a rotating sphere using a quasi-geostrophic model

We study nonlinear convection in a rapidly rotating sphere with internal heating for values of the Prandtl number relevant for liquid metals ($Pr\in [10^{-2},10^{-1}]$). We use a numerical model based on the quasi-geostrophic approximation, in which variations of the axial vorticity along the rotation axis are neglected, whereas the temperature field is fully three-dimensional. We identify two separate branches of convection close to onset: (i) a well-known weak branch for Ekman numbers greater than $10^{-6}$, which is continuous at the onset (supercritical bifurcation) and consists of thermal Rossby waves and (ii) a novel strong branch at lower Ekman numbers, which is discontinuous at the onset. The strong branch becomes subcritical for Ekman numbers of the order of $10^{-8}$. On the strong branch, the Reynolds number of the flow is greater than $10^{3}$, and a strong zonal flow with multiple jets develops, even close to the nonlinear onset of convection. We find that the subcriticality is amplified by decreasing the Prandtl number. The two branches can co-exist for intermediate Ekman numbers, leading to hysteresis ($Ek=10^{-6}$, $Pr=10^{-2}$). Nonlinear oscillations are observed near the onset of convection for $Ek=10^{-7}$ and $Pr=10^{-1}$.