Diversification of freshwater crabs on the sky islands in the Hengduan Mountains Region, China.

The numerous naturally-fragmented sky islands (SIs) in the Hengduan Mountains Region (HMR) of southwestern China constitute discontinuous landscapes where montane habitats are isolated by dry-hot valleys which have fostered exceptional species diversification and endemicity. However, studies documenting the crucial role of SI on the speciation dynamics of native freshwater organisms are scarce. Here we used a novel set of comprehensive genetic markers (24 nuclear DNA sequences and complete mitogenomes), morphological characters, and biogeographical information to reveal the evolutionary history and speciation mechanisms of a group of small-bodied montane potamids in the genus Tenuipotamon. Our results provide a robustly supported phylogeny, and suggest that the vicariance events of these montane crabs correlate well with the emergence of SIs due to the uplift of the HMR during the Late Oligocene. Furthermore, ancestrally, mountain ridges provided corridors for the dispersal of these montane crabs that led to the colonization of moist montane-specific habitats, aided by past climatic conditions that were the crucial determinants of their evolutionary history. The present results illustrated that the mechanisms isolating SIs are reinforced by the harsh-dry isolating climatic features of dry-hot valleys separating SIs and continue to affect local diversification. This offers insights into the causes of the high biodiversity and endemism shown by the freshwater crabs of the HMR-SIs in southwestern China.

Description of a New Species of Hua (Gastropoda: Semisulcospiridae) from Guizhou, China, Based on Morphology and Molecular Evidence.

A new species of Hua, Hua qiannanensis sp. nov., is described from Guizhou Province, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: the smooth shell, only three smaller cusps of lateral teeth on the inner side, outer marginal teeth with eight flattened and rounded denticles, an ovipositor pore in females, and BW/H ≥ 80%, B/H = 76.8-82.3%. Molecular analysis based on partial mitochondrial COI and 16S rDNA also supports the systematic position of the new taxon.

Dynamic methylome of internal mRNA N7-methylguanosine and its regulatory role in translation.

Over 150 types of RNA modifications are identified in RNA molecules. Transcriptome profiling is one of the key steps in decoding the epitranscriptomic panorama of these chemical modifications and their potential functions. N7-methylguanosine (m7G) is one of the most abundant modifications present in tRNA, rRNA and mRNA 5'cap, and has critical roles in regulating RNA processing, metabolism and function. Besides its presence at the cap position in mRNAs, m7G is also identified in internal mRNA regions. However, its transcriptome-wide distribution and dynamic regulation within internal mRNA regions remain unknown. Here, we have established m7G individual-nucleotide-resolution cross-linking and immunoprecipitation with sequencing (m7G miCLIP-seq) to specifically detect internal mRNA m7G modification. Using this approach, we revealed that m7G is enriched at the 5'UTR region and AG-rich contexts, a feature that is well-conserved across different human/mouse cell lines and mouse tissues. Strikingly, the internal m7G modification is dynamically regulated under both H2O2 and heat shock treatments, with remarkable accumulations in the CDS and 3'UTR regions, and functions in promoting mRNA translation efficiency. Consistently, a PCNA 3'UTR minigene reporter harboring the native m7G modification site displays both enriched m7G modification and increased mRNA translation upon H2O2 treatment compared to the m7G site-mutated minigene reporter (G to A). Taken together, our findings unravel the dynamic profiles of internal mRNA m7G methylome and highlight m7G as a novel epitranscriptomic marker with regulatory roles in translation.