The complete chloroplast genome and phylogenetic analysis of Cyperus malaccensis Lam (Cyperaceae).

Cyperus malaccensis Lam is a perennial herbaceous plant that is distributed over a large area along the southern coast of China. Some plants of the Cyperaceae family are highly similar morphologically, which makes them difficult to classify and identify. In this study, the complete chloroplast genome of C. malaccensis was sequenced and assembled. The chloroplast genome is 186,098 bp long with a 33.18% content of GC. The structure of chloroplast genome includes a quadripartite structure that is composed of a pair of inverted repeats (IRs) of 37,434 bp, a small single copy (SSC) region of 10,296 bp, and a large single copy (LSC) region of 100,934 bp. The genome contains 141 genes, including 94 protein-coding genes, 39 tRNA genes, and 8 rRNA genes. A phylogenetic analysis showed that C. malaccensis is the most closely related to the congeneric species C. rotundus. These results enrich the genetic resources of the Cyperaceae and provide a molecular basis for further study on the phylogeny of this family.

Abundant and Rare Taxa of Planktonic Fungal Community Exhibit Distinct Assembly Patterns Along Coastal Eutrophication Gradient.

Revealing planktonic fungal ecology under coastal eutrophication is crucial to our understanding of microbial community shift in marine pollution background. We investigated the diversity, putative interspecies interactions, assembly processes and environmental responses of abundant and rare planktonic fungal communities along a eutrophication gradient present in the Beibu Gulf. The results showed that Dothideomycetes and Agaricomycetes were the predominant classes of abundant and rare fungi, respectively. We found that eutrophication significantly altered the planktonic fungal communities and affected the abundant taxa more than the rare taxa. The abundant and rare taxa were keystone members in the co-occurrence networks, and their interaction was enhanced with increasing nutrient concentrations. Stochastic processes dominated the community assembly of both abundant and rare planktonic fungi across the eutrophication gradient. Heterogeneous selection affected abundant taxa more than rare taxa, whereas homogenizing dispersal had a greater influence on rare taxa. Influences of environmental factors involving selection processes were detected, we found that abundant fungi were mainly influenced by carbon compounds, whereas rare taxa were simultaneously affected by carbon, nitrogen and phosphorus compounds in the Beibu Gulf. Overall, these findings highlight the distinct ecological adaptations of abundant and rare fungal communities to marine eutrophication.

Climate and nutrients regulate biographical patterns and health risks of antibiotic resistance genes in mangrove environment.

Mangroves are prone to receive pollutants and act as a sink for antibiotic resistance genes (ARGs). However, knowledge of the human health risk of ARGs and its influencing factors in mangrove ecosystems is limited, particularly at large scales. Here, we applied a high-throughput sequencing technique combined with an ARG risk assessment framework to investigate the profiles of ARGs and their public health risks from mangrove wetlands across South China. We detected 456 ARG subtypes, and found 71 of them were identified as high-risk ARGs, accounting for 0.25 % of the total ARG abundance. Both ARGs and bacterial communities showed a distance-decay biogeography, but ARGs had a steeper slope. Linear regression analysis between features of co-occurrence network and high-risk ARG abundance implies that greater connections in the network would result in higher health risk. Structural equation models showed that geographic distance and MGEs were the most influential factors that affected ARG patterns, ARGs and MGEs contributed the most to the health risk profiles in mangrove ecosystems. This work provides a novel understanding of biogeographic patterns and health risk assessment of ARGs in mangrove ecosystems and can have profound significance for mangrove environment management with regard to ARG risk control.

Trophic states regulate assembly processes and network structures of small chromophytic phytoplankton communities in estuarine and coastal ecosystem.

Small chromophytic phytoplankton (SCP) are anticipated to be more important for a significant proportion of primary production in estuarine-coastal ecosystems. However, responses of SCP community to coastal eutrophication are still unclear. In this study, we investigated diversity, co-occurrence and assembly features of SCP communities, as well as relationship with environmental factors in subtropical Beibu Gulf. The results exhibited that the alpha diversity and beta diversity of SCP communities were significantly different among eutrophic states. Co-occurrence network revealed a complex interaction that most amplicon sequence variants (ASVs) in modules of the network were specific to trophic states. Further, phylogenetic based ß-nearest taxon distance analyses revealed that stochastic processes mainly provided 69.26% contribution to SCP community assembly, whereas deterministic processes dominated community assembly in heavy eutrophic state. Overall, our findings elucidate the mechanism of diversity and assembly in SCP community and promote the understanding of SCP ecology related to subtropical coastal eutrophication.

Human eutrophication drives biogeographic salt marsh productivity patterns in China.

Salt marshes are important natural carbon sinks with a large capacity to absorb exogenous nutrient inputs. The effects of nutrients on biogeographic productivity patterns, however, have been poorly explored in salt marshes. We conducted field surveys to examine how complex environments affect productivity of two common salt marsh plants, invasive Spartina alterniflora and native Phragmites australis, along an 18,000-km latitudinal gradient on the Chinese coastline. We harvested peak aboveground biomass as a proxy for productivity, and measured leaf functional traits (e.g., leaf area, specific leaf area [SLA], leaf nitrogen [N] and phosphorus [P]), soil nutrients (dissolved inorganic N [DIN] and available P [AP]), and salinity. We compiled data on mean annual temperature (MAT) and exogenous nutrients (both N and P). Then, we examined how these abiotic factors affect salt marsh productivity using both linear mixed effect models and structural equation modeling. Using a trait-based approach, we also examined how salt marsh productivity responds to changing environments across latitude. Exogenous nutrients (both N and P), compared with temperature and other variables (e.g., DIN, AP, salinity), were the dominant factors in explaining the biogeographic productivity patterns of both S. alterniflora and P. australis. Leaf size-related traits (e.g., leaf area), rather than leaf economic traits (e.g., SLA, leaf N and P), can be used to indicate the positive effects of exogenous nutrients on the productivity of these two species. Our results demonstrated that human eutrophication surpassed temperature as the major driver of biogeographic salt marsh productivity pattern, challenging current models in which biogeographic productivity pattern is primarily controlled by temperature. Our findings have potential broad implications for the management of S. alterniflora, which is a global invader, as it has benefited from coastal eutrophication. Furthermore, exogenous nutrient availability and leaf size need to be integrated into earth system models that are used to predict global plant productivity in salt marshes.

Complete mitochondrial genome of the Freshwater Whipray Himantura dalyensis.

The complete mitochondrial genome of the Freshwater Whipray Himantura dalyensis is presented in this study. It is 17,693 bp in length and contains 37 genes in typical gene order and transcriptional orientation observed in vertebrates. There were a total of 86 bp short intergenic spacers and 22 bp overlaps in the genome. The overall base composition was 31.4% A, 25.5% C, 13.2% G and 29.9% T. Two start codons (GTG and ATG) and two stop codons (TAG and TAA/T) were found in 13 protein-coding genes. The length of 22 tRNA genes ranged from 68 (tRNA-Cys and tRNA-Ser2) to 75 bp (tRNA-Leu1). The origin of L-strand replication (OL) was found between the tRNA-Asn and tRNA-Cys genes. The base composition of the control region (1940 bp) was similar to the whole mitogenome.

Complete mitogenome of the oriental sole Brachirus orientalis.

The complete mitochondrial genome of the oriental sole Brachirus orientalis was presented in this study. It is 16,600 bp in length, contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and 1 control region. A total of 28 bp short overlaps and 23 bp non-coding intergenic spacers were found in the mitogenome. The overall base composition of the L-strand is 30.5% A, 28.7% C, 15.2% G and 25.6% T. Two start codons (ATG and GTG) and three stop codons (AGG, TAG and TAA/T) were found in the protein-coding genes. Twenty-two tRNA genes ranged from 66 bp to 75 bp. Since the tRNA-Ser2 lacks the dihydrouridine arm it can not fold into a typical cloverleaf structure. The control region demonstrates the highest A+T content (66.4%) and the lowest G content (11.8%) in the mitogenome.

Mitochondrial genome of the spotless smooth-hound Mustelus griseus (Carcharhiniformes: Triakidae).

The complete mitochondrial genome of Mustelus griseus was first determined in this study. It is 16,754 bp in length, consisting of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and 1 control region with the typical gene order in vertebrates. Overall nucleotide base composition of the mitogenome is 30.7% A, 24.9% C, 14.0% G and 30.3% T. After aligning, it comes to us that the mitogenomic portions of M. griseus are very similar to those of Mustelus manazo, ranging from 86.92% (control region) to 100% (tRNA-His and tRNA-Leu2). The origin of L-strand replication (OL) is identified between tRNA-Asn and tRNA-Cys genes. The control region is located between the tRNA-Pro and tRNA-Phe genes, containing one termination-associated sequence (TAS) and three short conserved sequences (CSB 1-3).

Complete mitogenome of the brown guitarfish Rhinobatos schlegelii (Rajiformes, Rhinobatidae).

The complete mitochondrial genome of the brown guitarfish Rhinobatos schlegelii is presented for the first time in this study. It is 16,780 bp in length, consisting 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 putative control region with the typical gene order and direction of transcription in vertebrates. The overall base composition is 32.1% A, 26.3% C, 13.2% G and 28.3% T. Two start codon (GTG and ATG) and two stop codon patterns (TAG and TAA/T) were found in protein-coding genes. The 22 tRNA genes ranged from 67 (tRNA-Ser2) to 75 (tRNA-Leu1) bp in length. The origin of L-strand replication (OL) was between tRNA-Asn and tRNA-Cys genes within the WANCY region. The tRNA-Ser2 could not be fold into the typical cloverleaf secondary structure because of the replacement of its dihydrouridine arm by a simple loop. The control region was 1089 bp in length with high A + T content (64.0%).

The complete mitochondrial genome of the wavyband sole Pseudaesopia japonica (Pleuronectiformes: Soleidae).

The wavyband sole Pseudaesopia japonica is the only known member of the genus Pseudaesopia. In this study, we firstly determined the complete mitochondrial genome of P. japonica. It is 16,789 bp in length and contains two rRNA genes, 22 tRNA genes, 13 protein-coding genes and one putative control region with the typical gene order and transcriptional direction in vertebrates. The overall base composition of mitogenome in P. japonica is 28.4% A, 30.3% C, 15.6% G and 25.7% T. Two start codons (ATG and GTG) and four stop codons (AGA, AGG, TAG and TAA) were found in 13 protein-coding genes. The 22 tRNAs range from 67 bp (tRNA-Cys and tRNA-Tyr) to 75 bp (tRNA-Lys) in length. The control region is 1120 bp in length, representing a higher proportion of A + T (65.3%) while lower of G (12.0%).

Complete mitogenome of the peacock sole Pardachirus pavoninus (Pleuronectiformes: Soleidae).

The complete mitochondrial genome of the peacock sole Pardachirus pavoninus was firstly determined in this study. It is 16,537 bp in length, consisting of 13 protein-coding genes, two rRNA genes, 22 tRNA genes and one control region with the typical gene order in vertebrates. There are 26 bp overlaps and 28 bp short intergenic spaces located in 7 and 11 gene junctions, respectively. The overall nucleotide composition of the L-strand is 29.1% A, 29.5% C, 16.4% G and 25.0% T. The 22 tRNAs range from 65 bp (tRNA-Cys) to 74 bp (tRNA-Val, tRNA-Leu1, tRNA-Lys and tRNA-Thr) in length. Two start codons (ATG and GTG) and two stop codons (AGG and TAA/T) were found in 13 protein-coding genes.

Complete mitochondrial genome of the largest living fish: whale shark Rhincodon typus (Orectolobiformes: Rhincodontidae).

The whale shark Rhincodon typus (Pisces: Chondrichthyes, Orectolobiformes, Rhincodontidae) is the largest living fish on Earth. In this study, we presented its complete mitogenome. It is 16,928 bp in length, contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and one control region with the typical gene order and transcriptional direction in the vertebrates. Overall base composition of the R. typus mitogenome is 33.5% A, 24.3% C, 12.8% G and 29.5% T. Two start codon (GTG and ATG) and two stop codon patterns (TAG and TAA/T) were found in protein-coding genes. The tRNA-Ser2 could not be folded into the typical cloverleaf secondary structure because of the replacement of its dihydrouridine arm by a simple loop. A termination associated sequences (TAS) and three conserved sequence blocks (CSB1-3) were identified in the control region.

Complete mitogenome of the Areolate grouper Epinephelus areolatus (Serranidae, Epinephelinae).

In this study, we present the complete mitochondrial DNA sequences of Epinephelus areolatus for the first time, which is 16,893 bp in length and contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a putative control region. The overall base composition of the H-strand is 27.0% T, 28.0% C, 28.6% A, and 16.3% G. The CO1 gene is initiated by GTG codon and ATP6 gene is initiated by TTG codon. The tRNA-Ser2 cannot be folded into the typical cloverleaf secondary structure because its dihydrouridine arm is replaced by a simple loop. A long-tandem repeat motif (76 bp), repeated six times, is found in the control region.

Complete mitochondrial genome of the striped grouper Epinephelus latifasciatus (Serranidae, Epinephelinae).

The complete mitochondrial genome of the striped grouper Epinephelus latifasciatus is first presented in this study. The total length of E. latifasciatus is 16,389 bp, consisting of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and an A+T-rich control region. The gene order and transcriptional orientation are identical to those of most vertebrates. The total base composition is 28.6% A, 29.1% C, 26.4% T, and 16.0% G, with a slight A+T bias of 55.0%. The dihydrouridine arm of tRNA-Ser2 is replaced with one loop, because of which it cannot be folded into typical cloverleaf secondary structure. The termination-associated sequences and conserved sequence blocks (CSB1-3) are found in the control region.