BackgroundThe Chinese salamander (Hynobius chinensis), an endangered amphibian species of salamander endemic to China, has attracted much attention because of its value of studying paleontology evolutionary history and decreasing population size. Despite increasing interest in the Hynobius chinensis genome, genomic resources for the species are still very limited. A comprehensive transcriptome of Hynobius chinensis, which will provide a resource for genome annotation, candidate genes identification and molecular marker development should be generated to supplement it.Principal FindingsWe performed a de novo assembly of Hynobius chinensis transcriptome by Illumina sequencing. A total of 148,510 nonredundant unigenes with an average length of approximately 580 bp were obtained. In all, 60,388 (40.66%) unigenes showed homologous matches in at least one database and 33,537 (22.58%) unigenes were annotated by all four databases. In total, 41,553 unigenes were categorized into 62 sub-categories by BLAST2GO search, and 19,468 transcripts were assigned to 140 KEGG pathways. A large number of unigenes involved in immune system, local adaptation, reproduction and sex determination were identified, as well as 31,982 simple sequence repeats (SSRs) and 460,923 putative single nucleotide polymorphisms (SNPs).ConclusionThis dataset represents the first transcriptome analysis of the Chinese salamander (Hynobius chinensis), an endangered species, to be also the first time of hynobiidae. The transcriptome will provide valuable resource for further research in discovery of new genes, protection of population, adaptive evolution and survey of various pathways, as well as development of molecule markers in Chinese salamander; and reference information for closely related species.

BackgroundThe miiuy croaker (Miichthys miiuy) is an important species of marine fish that supports capture fisheries and aquaculture. At present commercial scale aquaculture of this species is limited due to diseases caused by pathogens and parasites which restrict production and limit commercial value. The lack of transcriptomic and genomic information for the miiuy croaker limits the ability of researchers to study the pathogenesis and immune system of this species. In this study we constructed a cDNA library from liver, spleen and kidney which was sequenced using Illumina paired-end sequencing to enable gene discovery and molecular marker development.Principal FindingsIn our study, a total of 69,071 unigenes with an average length of 572 bp were obtained. Of these, 45,676 (66.13%) were successfully annotated in public databases. The unigenes were also annotated with Gene Ontology, Clusters of Orthologous Groups and KEGG pathways. Additionally, 498 immune-relevant genes were identified and classified. Furthermore, 14,885 putative simple sequence repeats (cSSRs) and 8,510 putative single nucleotide polymorphisms (SNPs) were identified from the 69,071 unigenes.ConclusionThe miiuy croaker (Miichthys miiuy) transcriptome data provides a large resource to identify new genes involved in many processes including those involved in the response to pathogens and diseases. Furthermore, the thousands of potential cSSR and SNP markers found in this study are important resources with respect to future development of molecular marker assisted breeding programs for the miiuy croaker.

The miiuy croaker, Miichthys miiuy, is a representative Sciaenidae known for its exceptionally large otoliths. This species mainly inhabits turbid aquatic environments with mud to sandy mud bottoms. However, the characteristics of the immune system of this organism and its specific aquatic environment adaptations are poorly understood. Thus, we present a high-quality draft genome of miiuy croaker. The expansions of several gene families which are critical for the fish innate immune system were identified. Compared with the genomes of other fishes, some changes have occurred in the miiuy croaker sensory system including modification of vision and expansion of taste and olfaction receptors. These changes allow miiuy croaker to adapt to the environment during the long-term natural selection. The genome of miiuy croaker may elucidate its relatively well-developed immune defense and provide an adaptation model of the species thriving in turbid deep aquatic environments.

Leptospirosis is a zoonotic disease caused by pathogenic Leptospira. However, understanding of the pathogenic mechanism of Leptospira is still elusive due to the limited number of genetic tools available for this microorganism. Currently, the reason for the genetic inaccessibility of Leptospira is still unknown. It is well known that as an acquired immunity of bacteria, Clustered Regularly Interspaced Short Palindromic Repeat‐CRISPR‐associated gene (CRISPR‐Cas) systems can help bacteria against invading mobile genetic elements. In this study, the occurrence and diversity of CRISPR‐Cas systems in 41 genomes of Leptospira strains were investigated. Three subtypes (subtype I‐B, subtype I‐C and subtype I‐E) of CRISPR‐Cas systems were identified in both pathogenic and intermediate Leptospira species but not in saprophytic species. Noteworthy, the majority of pathogenic species harbor two different types of CRISPR‐Cas systems (subtype I‐B and subtype I‐E). Furthermore, Cas2 protein of subtype I‐C in L. interrogans exhibited a metal‐dependent DNase activity in a nonspecific manner. CRISPR spacers in subtype I‐B are highly conserved within the same serovars and hypervariable across different serovars of L. interrogans. Based on the subtype I‐B CRISPR arrays, the serotypes of different L. interrogans strains were easily identified. Investigation of the origin of CRISPR spacers showed that 192 spacers (23.5%) matched to mobile genetic elements, indicating CRISPR‐Cas systems may play an important role in the defense of foreign invading DNA.

Leptospirosis is a widespread zoonotic disease caused by pathogenic Leptospira species. The most common species, Leptospira interrogans, can transfer from contaminated soil or water to the human body. It is able to survive these changing environments through sensing and responding to the changes of environmental cues. Cyclic di-GMP (c-di-GMP) is a special secondary messenger in bacteria, which can respond to the environment and regulate diverse bacterial behaviors. The c-di-GMP levels in bacterial cells are regulated by diguanylatecyclases (DGC) and phosphodiesterases (PDE), which are responsible for synthesizing or hydrolyzing c-di-GMP, respectively. In this study, distribution and phylogenetics of c-di-GMP metabolic genes among 15 leptospiral species were systematically analyzed. Bioinformatics analysis revealed that leptospiral species contain a multitude of c-di-GMP metabolic genes. C-di-GMP metabolic genes in L. interrogans strain Lai 56601 were further analyzed and the results showed that these genes have very diverse expression patterns. Most of the putative DGCs and PDEs possess enzymatic activities, as determined by riboswitch-based dual-fluorescence reporters in vivo or HPLC in vitro. Furtherer analysis of subdomains from GGDEF-containing proteins revealed that the ability to synthesize c-di-GMP was lost when the GAF domain from LA1483 and PAS domain from LA2932 were deleted, while deletion of the REC domain from LA2528 did not affect its ability to synthesize c-di-GMP. Furthermore, high temperatures generally resulted in low c-di-GMP concentrations in L. interrogans and most of the c-di-GMP metabolic genes exhibited differential temperature regulation. Also, infection of murine J774A.1 cells resulted in reduced c-di-GMP levels, while no significant change of c-di-GMP metabolic genes on transcriptional levels were observed during the infection of J774A.1 cells. Taken together, these results provide a basic platform for future studies of c-di-GMP signaling pathways in Leptospira.