Frog Amolops Research Articles

Synergistic collaboration between AMPs and non-direct antimicrobial cationic peptides

Non-direct antimicrobial cationic peptides (NDACPs) are components of the animal innate immune system. But their functions and association with antimicrobial peptides (AMPs) are incompletely understood. Here, we reveal a synergistic interaction between the AMP AW1 and the NDACP AW2, which are co-expressed in the frog Amolops wuyiensis. AW2 enhances the antibacterial activity of AW1 both in vitro and in vivo, while mitigating the development of bacterial resistance and eradicating biofilms. AW1 and AW2 synergistically damage bacterial membranes, facilitating cellular uptake and interaction of AW2 with the intracellular target bacterial genomic DNA. Simultaneously, they trigger the generation of ROS in bacteria, contributing to cell death upon reaching a threshold level. Moreover, we demonstrate that this synergistic antibacterial effect between AMPs and NDACPs is prevalent across diverse animal species. These findings unveil a robust and previously unknown correlation between AMPs and NDACPs as a widespread antibacterial immune defense strategy in animals.

Progressive Design of a Ranatuerin-2 Peptide from Amolops wuyiensis: Enhancement of Bioactivity and In Vivo Efficacy.

Antimicrobial peptides (AMPs) that exert multiple functions are considered promising candidates to combat the bacterial drug resistance crisis. Nowadays, targeted peptide modification has been widely recognised to improve biological activity and make up for deficiencies in clinical applications such as toxicity. In this study, a helix-loop peptide was isolated and identified from the skin secretion of the Wuyi torrent frog Amolops wuyiensis, namely, ranatuerin-2-AW (R2AW) (GFMDTAKNVAKNVAATLLDKLKCKITGGC). Target modifications were made to R2AW to study the structure-activity relationships and to optimise its bioactivities. Five analogues were progressively designed via residue substitution and truncation and the antibacterial and anticancer activities were evaluated. We found that the serine-substitution and cyclic-domain-deletion products showed similar antibacterial activity to the natural peptide R2AW, implying that the disulphide bridge and Rana box were dispensable for the antibacterial activity of ranatuerin-2 peptides. Notably, the cationicity- and hydrophobicity-enhanced variant, [Lys4,19, Leu20]R2AW(1-22)-NH2, exhibited significantly optimised antibacterial and anticancer activities. Additionally, it killed bacteria by membrane disruption at a highly efficient rate. Moreover, [Lys4,19, Leu20]R2AW(1-22)-NH2 exerted potential in vivo efficacy in a methicillin-resistant Staphylococcus aureus (MRSA)-infected waxworm model. Overall, this study demonstrated some rational design ideas for optimising the dual antibacterial and anticancer activities of ranatuerin-2 peptides and it proposes [Lys4,19, Leu20]R2AW(1-22)-NH2 as an appealing candidate for therapeutic development.

Systematics of the Lao torrent frog, Amolops cremnobatus Inger & Kottelat, 1998 (Anura: Ranidae), with descriptions of four new species

Abstract The Lao torrent frog Amolops cremnobatus Inger & Kottelat, 1998 was recently hypothesized, based on mitochondrial DNA, to consist of more than a single species across its range in Laos and flanking regions of Vietnam and Thailand. We tested this hypothesis using mitochondrial DNA, nuclear DNA, and quantitative and qualitative morphological data from adults and larvae. We found corroborating lines of evidence for five distinct evolutionary lineages that we hypothesize to be species. Amolops cremnobatus sensu stricto is restricted to the southeastern portion of its previous range, and remaining populations are described as four new species. Some of the new species are easier to diagnose with morphology as larvae than as adults. Further sampling in northern Thailand may reveal an additional species of this torrent frog complex.

New Distribution Record of Himalayan Water Shrew Chimarrogale himalayica (Gray, 1842) Soricomorpha: Soricidae and its Attempt to Feed on a Cascade Frog Amolops sp. from Jaintia Hills, Meghalaya, India.

New Distribution Record of Himalayan Water Shrew Chimarrogale himalayica (Gray, 1842) Soricomorpha: Soricidae and its Attempt to Feed on a Cascade Frog Amolops sp. from Jaintia Hills, Meghalaya, India.

Large X-effects are absent in torrent frogs with nascent sex chromosomes.

Sex chromosomes are popularized as a special role in driving speciation. However, the empirical evidence from natural population processes has been limited to organisms with degenerated sex chromosomes, where hemizygosity is mainly considered to act as the driver of reproductive isolation. Here, we examined several hybrid zones of torrent frog Amolops mantzorum species complex, using an approach by mapping species-diagnostic loci onto the reference genome to compare sex-linked versus autosomal patterns of introgression. We find little support in sex-linked incompatibilities for large X-effects for these populations in hybrid zones with homomorphic sex chromosomes, due to the absence of the hemizygous effects. As expected, the large X-effects were not found in those with heteromorphic but newly evolved sex chromosomes, owing to the absence of strong genetic differences between X and Y chromosomes. The available data so far on amphibians suggest little role for sex-linked genes in speciation. The large X-effects in those with nascent sex chromosomes may not be as ubiquitous as presumed across the animal kingdom.

Phylogenetic position of the poorly known montane cascade frog Amolops monticola (Ranidae) and description of a new closely related species from Northeast India

ABSTRACT The phylogenetic position of Amolops monticola, a cascade frog species known for over 150 years, remains unknown. Yet over the years new taxa have been frequently described in the ambiguously recognised A. monticola species group, based on morphology and presumed phylogenetic affinities. Here we report fresh collections of A. monticola from the Indian Himalayas and clarify its identity with new molecular and morphological evidence. Furthermore, our surveys in the Northeast Indian State of Arunachal Pradesh have led to the discovery of another new species in the A. monticola group from Siang River basin encompassing the Adi hills (historically known as Abor hills). The new species, formally described as Amolops adicola sp. nov., is morphologically distinguished from its congeners by a suite of characters that include adult size, body colouration and markings, skin texture, snout shape, foot webbing and digit tip morphology, in addition to significant morphometric distinctness observed in principal component analysis. Phylogenetically, the new species is recovered as a well-supported sister taxon of A. monticola, based on Bayesian and maximum likelihood inferences as well as Bayesian Poisson Tree Processes (bPTP) species delimitation analysis using 2001 bp of mitochondrial DNA (16S rRNA, cytochrome c oxidase subunit I and NADH dehydrogenase 2). It differs from other known members of the group by considerable genetic distances in the studied loci: ≥ 4.3% at 16S, ≥ 6.1% at COI and ≥ 7.0% at ND2. The study also shows for the first time the phylogenetic affinities of another Indian member of the A. monticola group, A. kohimaensis. Altogether, the new insights resolve the long-existing enigma surrounding A. monticola and facilitate a better understanding of systematic relationships within the large A. monticola species group. Our findings also emphasise the need for further dedicated studies on the cascade frogs of Northeast India.

A novel Kunitz-type neurotoxin peptide identified from skin secretions of the frog Amolops loloensis

A novel Kunitz-type neurotoxin peptide that inhibited voltage-gated sodium channel was purified and characterized from the skin secretions of rufous-spotted torrent frog, Amolops loloensis. It has a 240-bp cDNA encoding an 79-amino acid residue (aa) precursor protein containing 6 half-cysteines. The precursor was proven to release a 57-aa mature peptide with amino acid sequence, DRNPICNLPPKEGFCLWMMRRSFFNPSKGRCDTFGYRGCGGNKNNFETPRACKEACG. The mature was named amotoxin. Amotoxin shares sequence homology with other Kunitz-type toxins and also has three cysteine bridges. Amotoxin showed an inhibitory ability against trypsin with an inhibitory constant (Ki) of 0.087 μM. To the best of our knowledge, this is the first gene-encoded neurotoxin found in Amolops loloensis. Recombinant amotoxin showed similar functional properties as the native amotoxin. The functional properties of amotoxin may provide insights into the ecological adaptation of amphibians and deepen our understanding about the biological function spectrum of amphibian skin peptides.

Bv8-Like Toxin from the Frog Venom of Amolops jingdongensis Promotes Wound Healing via the Interleukin-1 Signaling Pathway.

Prokineticins are highly conserved small peptides family expressed in all vertebrates, which contain a wide spectrum of functions. In this study, a prokineticin homolog (Bv8-AJ) isolated from the venom of frog Amolops jingdongensis was fully characterized. Bv8-AJ accelerated full-thickness wounds healing of mice model by promoting the initiation and the termination of inflammatory phase. Moreover, Bv8-AJ exerted strong proliferative effect on fibroblasts and keratinocytes isolated from newborn mice by activating interleukin (IL)-1 production. Our findings indicate that Bv8 is a potent wound healing regulator and may reveal the mechanism of rapid wound-healing in amphibian skins.

Sometimes noise is beneficial: stream noise informs vocal communication in the little torrent frog Amolops torrentis

Many kinds of environmental noise can interfere with acoustic communication and efficient decision making in terrestrial species. Here we identified an exception to this generalization in a streamside species, the little torrent frog (Amolops torrentis) which communicates in a stream noise environment. To determine whether stream noise can act as a cue regarding the microhabitat characteristics of senders, we performed phonotaxis experiments using stimulus pairs constructed with synthetic male calls (high or low dominant frequency) and stream noise with varied signal-to-noise ratios. We found that females prefer calls with high amplitude stream noise added compared to those with low amplitude stream noise added for both high and low dominant frequency stimulus pairs; however, stream noise itself was not attractive in the absence of calls. These results show that stream noise can function as a cue that may be used by females for enhancing the attractiveness of calls. Stream noise associates closely with rocks, topographies and vegetation and may thus provide useful microhabitat information for signal receivers, thereby acting on sexual selection. These data therefore contribute to our understanding of how the perception of mate attractiveness in heterogeneous ecological environments can evolve.

A novel ranacyclin-like peptide with anti-platelet activity identified from skin secretions of the frog Amolops loloensis

Albeit many bioactive peptides have been reported from amphibian skins, no anti-platelet peptide has been identified till to date. Here, an anti-platelet peptide, namely Zongdian platelet inhibitor (ZDPI), with the molecular weight of 1798.6Da, was purified and characterized from skin secretions of the frog, Amolops loloensis. The amino acid sequence of ZDPI was determined as FRGCWLKNYSPRGCL-NH2 by combination methods of Edman degradation, mass spectrometry analysis and carboxypeptidase Y treatment revealing that it is composed of 15 amino acid residues with two cysteines formed an intra-molecular disulfide bridge and C-terminal amidation. cDNA encoding ZDPI precursor was cloned from skin cDNA library of A. loloensis. The precursor is composed of 63 amino acid (aa) residues including the predicted signal peptide (22aa), an acidic spacer peptide (19aa), and mature ZDPI. BLAST search indicates that ZDPI belongs to antimicrobial peptide family of ranacyclin, peptide leucine arginine or odorranain. It was found to inhibit ADP-induced platelet aggregation in a dose-dependent manner. At the concentration of 32μg/ml, ZDPI completely inhibited platelet aggregation induced by ADP. To the best of our knowledge, this is the first report about an anti-platelet peptide from amphibian skin secretions. Considering its strong inhibitory ability on platelets and simple structure, ZDPI might be an excellent candidate or template to develop anti-thrombosis agent. In addition, the discovery of anti-platelet peptide in the frog skin increases biological function spectrum of amphibian skin peptides.

The complete mitochondrial genome of Amolops ricketti (Amphidia, Anura, Ranidae)

The complete mitochondrial genome from the South China torrent frog Amolops ricketti was determined. This mitogenome was 17,771 bp in length, containing 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a control region (CR). All the protein-coding genes in A. ricketti were distributed on the H-strand, except for the ND6 subunit gene and eight tRNA genes which were encoded on the L-strand.

Two novel families of antimicrobial peptides from skin secretions of the Chinese torrent frog, Amolops jingdongensis

The characterization of new natural antimicrobial peptides (AMPs) can help to solve the serious problem of bacterial resistance to currently used antibiotics. In the current study, we analyzed two families of AMPs from the Chinese torrent frog Amolops jingdongensis with a range of bioactivities. The first family of peptides, named jindongenin-1a, is 24 amino acids in length; a BLAST search of jindongenin-1a revealed no sequence similarity with other AMPs. The second family consists of two peptides containing 29 amino acid residues each. These peptides have high sequence similarity with the AMPs of palustrin-2 and are therefore designated palustrin-2AJ1 and palustrin-2AJ2. The cDNA sequences encoding these AMPs have been cloned and the deduced protein sequence of each AMP has been determined by protein sequencing. Sequence and structural analysis showed that each precursor is composed of a putative signal peptide, an N-terminal spacer, a processing site and a disulfide-bridged heptapeptide segment at the C-terminus. We synthesized jindongenin-1a and palustrin-AJ1 to test their antimicrobial, hemolytic, antioxidative and cytotoxic activities. These two peptides showed broad-spectrum antimicrobial activity to standard and clinically isolated strains of bacteria. In addition, they exhibited weak hemolytic activity to human and rabbit erythrocytes under our experimental conditions. Moreover, these peptides also displayed cytotoxic activity against the K562 and HT29 mammalian cell lines and low anti-oxidant activity. These findings provide helpful insight that will be useful in the design of anti-infective peptide agents.

A novel algesic peptide derived from skin secretions of the frog Amolops loloensis

Several algesic agents including bradykinin and tachykinin have been identified from skin secretions of amphibians. They may act in defensive roles against aggressors. In this study, a novel peptide named Amolos with an amino acid sequence of FLPIVGAKL and isolated from skin secretion of the frog Amolops loloensis, is shown to strengthen nociceptive responses induced by inflammatory factors and strongly inhibit the contraction of isolated ileum. A synthetic peptide based on the sequence obtained showed characterization data identical to those of the isolated material, confirming its structure. These two types of responses seem to be a part of the defensive functions against predators or aggressors. The current results suggest that pharmacological molecules in amphibian skins not only act as innate defense mechanisms against microorganisms but also exert other defensive physiological functions against other aggressors.

Paraphyly of Chinese Amolops (Anura, Ranidae) and phylogenetic position of the rare Chinese frog, Amolops tormotus

In order to evaluate the five species groups of Chinese Amolops based on morphological characteristics, and to clarify the phylogenetic position of the concave-eared torrent frog Amolops tormotus, we investigated the phylogeny of Amolops by maximum parsimony, Bayesian Inference, and maximum likelihood methods using two mitochondrial DNA fragments (12S rRNA, 16S rRNA). Our results supported a sister group relationship of Amolops ricketti and Amolops hainanensis. However, the grouping of Amolops mantzorum and Amolops monticola needs to be resolved with more data. Amolops tormotus was nested in genus Odorrana. Thus, recognition of the A. tormotus group is unwarranted and A. tormotus should be referred to genus Odorrana as O. tormota. This species is the sister group of O. nasica plus O. versabilis. The new classification implies that the genus Wurana is to be considered as junior subjective synonym of Odorrana.

Reproductive variation in the Torrent frog Amolops larutensis (Boulenger)

Journal Article Reproductive variation in the Torrent frog Amolops larutensis (Boulenger) Get access P. Y. Berry, P. Y. Berry Search for other works by this author on: Oxford Academic Google Scholar G. Varughese G. Varughese Search for other works by this author on: Oxford Academic Google Scholar Zoological Journal of the Linnean Society, Volume 47, Issue 313, October 1968, Pages 547–559, https://doi.org/10.1111/j.1096-3642.1968.tb00550g.x Published: 05 May 2011