Sichuan hot-spring snakes imperiled:reason,situation,and protection

The Sichuan hot-spring snake(Thermophis zhaoermii)is a rare and endemic species found at high elevations in the Hengduan Mountains of China.Recent species-specific investigations showed that the Sichuan hot-spring snake is still restricted to geothermal zones at elevations higher than 3000 m a.s.l.The species also remains at risk of extinction,with the effective population size showing continual decline over the past one million years based on coalescent inference from genome-level single nucleotide polymorphism(SNP)data.We propose several approaches for protecting Sichuan hot-spring snake populations and their habitat.

Developmental regulation of conserved non-coding element evolution provides insights into limb loss in squamates

Limb loss shows recurrent phenotypic evolution across squamate lineages.Here,based on three de novo-assembled genomes of limbless lizards from different lineages,we showed that divergence of conserved non-coding elements(CNEs)played an important role in limb development.These CNEs were associated with genes required for limb initiation and outgrowth,and with regulatory signals in the early stage of limb development.Importantly,we identified the extensive existence of insertions and deletions(In Dels)in the CNEs,with the numbers ranging from 111 to 756.Most of these CNEs with In Dels were lineagespecific in the limbless squamates.Nearby genes of these In Del CNEs were important to early limb formation,such as Tbx4,Fgf10,and Gli3.Based on functional experiments,we found that nucleotide mutations and In Dels both affected the regulatory function of the CNEs.Our study provides molecular evidence underlying limb loss in squamate reptiles from a developmental perspective and sheds light on the importance of regulatory element In Dels in phenotypic evolution.

Aggregation-induced emission and self-assembly of functional tetraphenylethene-based tetracationic dicyclophanes for selective detection of ATP in water

Functional dicyclophanes with various substituents(e.g.,NO_(2),Br,OCH_(3)and OH)were synthesized via one-pot S_(N)2 reaction.Dicyclophanes can form nanospheres via the head-to-tail self-assembly between the cavities and the TPE units to exhibit aggregation-induced emission(AIE)in aqueous solution.These AIE-active nanospheres with cationic feature exhibited selective recognition with fluorescence response for anionic ATP via electrostatic interactions and hydrophobic effects in water.

Successive construction of cucurbit[8]uril-based covalent organic frameworks from a supramolecular organic framework through photochemical reactions in water

Functional framework materials have been developed for many applications including adsorption, asymmetric catalysis, sensing,drug delivery, optical device, and so on. Here, we report the successive construction of two cucurbit[8]uril-based covalent organic frameworks(COFs) including tetraphenylethene-based COF(COF-1) and phenanthrene-based COF(COF-2) from a two-dimensional(2D) periodic cucurbit[8]uril-based supramolecular organic framework(SOF-1) as the prearranged structure via the intermolecular photocycloaddition of the coumarin units and the intramolecular photocyclization of the tetraphenylethene(TPE) units under ultraviolet(UV) irradiation(365 nm) in water. In this case, oxygen(O_(2)) plays an important role in the photocyclization of the TPE units into the phenanthrene units in the transform process from SOF-1 or COF-1 to COF-2. As the TPE units further form phenanthrenes after UV-irradiation, COF-2 exhibits aggregation-caused quenching effect and weak green emission, while COF-1 displays a strong yellow emission due to the aggregation-induced emission. Besides, the adaptive chirality of cationic COF-1 as a biomolecular sensor can be efficiently induced by chiral anionic biomolecules including adenosine-5′-triphosphate(ATP) and adenosine-5′-diphosphate(ADP) to exhibit sensitive negative circular dichroism responses in water. This supramolecular approach to construct COF from SOF via photochemical reactions may open a new opportunity for the construction and application of the water-soluble COFs with well structural controllability, unique photophysical properties,and favorable biocompatibility.

Temperature acclimation in hot-spring snakes and the convergence of cold response

Animals have evolved sophisticated temperature-sensing systems and mechanisms to detect and respond to ambient temperature changes.As a relict species endemic to the Qinghai-Tibet Plateau,hot-spring snake(Thermophis baileyi)survived the dramatic changes in climate that occurred during plateau uplift and ice ages,providing an excellent opportunity to explore the evolution of temperature sensation in ectotherms.Based on distributional information and behavioral experiments,we found that T.baileyi prefer hotspring habitats and respond more quickly to warmth than other two snakes,suggesting that T.baileyi may evolve an efficient thermal-sensing system.Using high-quality chromosome-level assembly and comparative genomic analysis,we identified cold acclimation genes experiencing convergent acceleration in high-altitude lineages.We also discovered significant evolutionary changes in thermosensation-and thermoregulation-related genes,including the transient receptor potential(TRP)channels.Among these genes,TRPA1 exhibited three species-specific amino acid replacements,which differed from those found in infrared imaging snakes,implying different temperature-sensing molecular strategies.