Genome-Wide Characterization and Linkage Mapping of Simple Sequence Repeats in Mei (Prunus mume Sieb. et Zucc.)

Because of its popularity as an ornamental plant in East Asia, mei (Prunus mume Sieb. et Zucc.) has received increasing attention in genetic and genomic research with the recent shotgun sequencing of its genome. Here, we performed the genome-wide characterization of simple sequence repeats (SSRs) in the mei genome and detected a total of 188,149 SSRs occurring at a frequency of 794 SSR/Mb. Mononucleotide repeats were the most common type of SSR in genomic regions, followed by di- and tetranucleotide repeats. Most of the SSRs in coding sequences (CDS) were composed of tri- or hexanucleotide repeat motifs, but mononucleotide repeats were always the most common in intergenic regions. Genome-wide comparison of SSR patterns among the mei, strawberry (Fragaria vesca), and apple (Malus×domestica) genomes showed mei to have the highest density of SSRs, slightly higher than that of strawberry (608 SSR/Mb) and almost twice as high as that of apple (398 SSR/Mb). Mononucleotide repeats were the dominant SSR motifs in the three Rosaceae species. Using 144 SSR markers, we constructed a 670 cM-long linkage map of mei delimited into eight linkage groups (LGs), with an average marker distance of 5 cM. Seventy one scaffolds covering about 27.9% of the assembled mei genome were anchored to the genetic map, depending on which the macro-colinearity between the mei genome and Prunus T×E reference map was identified. The framework map of mei constructed provides a first step into subsequent high-resolution genetic mapping and marker-assisted selection for this ornamental species.     

Molecular evolution and SSRs analysis based on the chloroplast genome of Callitropsis funebris

Chloroplast genome sequences have been used to understand evolutionary events and to infer efficiently phylogenetic relationships. Callitropsis funebris (Cupressaceae) is an endemic species in China. Its phylogenetic position is controversial due to morphological characters similar to those of Cupressus, Callitropsis, and Chamaecyparis. This study used next‐generation sequencing technology to sequence the complete chloroplast genome of Ca. funebris and then constructed the phylogenetic relationship between Ca. funebris and its related species based on a variety of data sets and methods. Simple sequence repeats (SSRs) and adaptive evolution analysis were also conducted. Our results showed that the monophyletic branch consisting of Ca. funebris and Cupressus tonkinensis is a sister to Cupressus, while Callitropsis is not monophyletic; Ca. nootkatensis and Ca. vietnamensis are nested in turn at the base of the monophyletic group Hesperocyparis. The statistical results of SSRs supported the closest relationship between Ca. funebris and Cupressus. By performing adaptive evolution analysis under the phylogenetic background of Cupressales, the Branch model detected three genes and the Site model detected 10 genes under positive selection; and the Branch‐Site model uncovered that rpoA has experienced positive selection in the Ca. funebries branch. Molecular analysis from the chloroplast genome highly supported that Ca. funebris is at the base of Cupressus. Of note, SSR features were found to be able to shed some light on phylogenetic relationships. In short, this chloroplast genomic study has provided new insights into the phylogeny of Ca. funebris and revealed multiple chloroplast genes possibly undergoing adaptive evolution.     

Integrated analysis of three newly sequenced fern chloroplast genomes: Genome structure and comparative analysis

BackgroundSome ferns have medicinal properties and are used in therapeutic interventions. However, the classification and phylogenetic relationships of ferns remain incompletely reported. Considering that chloroplast genomes provide ideal information for species identification and evolution, in this study, three unpublished and one published ferns were sequenced and compared with other ferns to obtain comprehensive information on their classification and evolution.Materials and MethodsThe complete chloroplast genomes of Dryopteris goeringiana (Kunze) Koidz, D. crassirhizoma Nakai, Athyrium brevifrons Nakai ex Kitagawa, and Polystichum tripteron (Kunze) Presl were sequenced using the Illumina HiSeq 4,000 platform. Simple sequence repeats (SSRs), nucleotide diversity analysis, and RNA editing were investigated in all four species. Genome comparison and inverted repeats (IR) boundary expansion and contraction analyses were also performed. The relationships among the ferns were studied by phylogenetic analysis based on the whole chloroplast genomes.ResultsThe whole chloroplast genomes ranged from 148,539 to 151,341 bp in size and exhibited typical quadripartite structures. Ten highly variable loci with parsimony informative (Pi) values of > 0.02 were identified. A total of 75–108 SSRs were identified, and only six SSRs were present in all four ferns. The SSRs contained a higher number of A + T than G + C bases. C‐to‐U conversion was the most common type of RNA editing event. Genome comparison analysis revealed that single‐copy regions were more highly conserved than IR regions. IR boundary expansion and contraction varied among the four ferns. Phylogenetic analysis showed that species in the same genus tended to cluster together with and had relatively close relationships.ConclusionThe results provide valuable information on fern chloroplast genomes that will be useful to identify and classify ferns, and study their phylogenetic relationships and evolution.     

Genome-wide analysis of simple sequence repeats in the model medicinal mushroom Ganoderma lucidum

Simple sequence repeats (SSRs) or microsatellites are one of the most popular sources of genetic markers and play a significant role in gene function and genome organization. We identified SSRs in the genome of Ganoderma lucidum and analyzed their frequency and distribution in different genomic regions. We also compared the SSRs in G. lucidum with six other Agaricomycetes genomes: Coprinopsis cinerea, Laccaria bicolor, Phanerochaete chrysosporium, Postia placenta, Schizophyllum commune and Serpula lacrymans. Based on our search criteria, the total number of SSRs found ranged from 1206 to 6104 and covered from 0.04% to 0.15% of the fungal genomes. The SSR abundance was not correlated with the genome size, and mono- to tri-nucleotide repeats outnumbered other SSR categories in all of the species examined. In G. lucidum, a repertoire of 2674 SSRs was detected, with mono-nucleotides being the most abundant. SSRs were found in all genomic regions and were more abundant in non-coding regions than coding regions. The highest SSR relative abundance was found in introns (108 SSRs/Mb), followed by intergenic regions (84 SSRs/Mb). A total of 684 SSRs were found in the protein-coding sequences (CDSs) of 588 gene models, with 81.4% of them being tri- or hexa-nucleotides. After scanning for InterPro domains, 280 of these genes were successfully annotated, and 215 of them could be assigned to Gene Ontology (GO) terms. SSRs were also identified in 28 bioactive compound synthesis-related gene models, including one 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), three polysaccharide biosynthesis genes and 24 cytochrome P450 monooxygenases (CYPs). Primers were designed for the identified SSR loci, providing the basis for the future development of SSR markers of this medicinal fungus.     

The complete chloroplast genomes of three Hamamelidaceae species: Comparative and phylogenetic analyses

Hamamelidaceae is an important group that represents the origin and early evolution of angiosperms. Its plants have many uses, such as timber, medical, spice, and ornamental uses. In this study, the complete chloroplast genomes of Loropetalum chinense (R. Br.) Oliver, Corylopsis glandulifera Hemsl., and Corylopsis velutina Hand.‐Mazz. were sequenced using the Illumina NovaSeq 6000 platform. The sizes of the three chloroplast genomes were 159,402 bp (C. glandulifera), 159,414 bp (C. velutina), and 159,444 bp (L. chinense), respectively. These chloroplast genomes contained typical quadripartite structures with a pair of inverted repeat (IR) regions (26,283, 26,283, and 26,257 bp), a large single‐copy (LSC) region (88,134, 88,146, and 88,160 bp), and a small single‐copy (SSC) region (18,702, 18,702, and 18,770 bp). The chloroplast genomes encoded 132–133 genes, including 85–87 protein‐coding genes, 37–38 tRNA genes, and 8 rRNA genes. The coding regions were composed of 26,797, 26,574, and 26,415 codons, respectively, most of which ended in A/U. A total of 37–43 long repeats and 175–178 simple sequence repeats (SSRs) were identified, and the SSRs contained a higher number of A + T than G + C bases. The genome comparison showed that the IR regions were more conserved than the LSC or SSC regions, while the noncoding regions contained higher variability than the gene coding regions. Phylogenetic analyses revealed that species in the same genus tended to cluster together. Chunia Hung T. Chang, Mytilaria Lecomte, and Disanthus Maxim. may have diverged early and Corylopsis Siebold & Zucc. was closely related to Loropetalum R. Br. This study provides valuable information for further species identification, evolution, and phylogenetic studies of Hamamelidaceae plants.     

Genome-Wide Identification of SSR and SNP Markers Based on Whole-Genome Re-Sequencing of a Thailand Wild Sacred Lotus (Nelumbo nucifera)

Genomic resources such as single nucleotide polymorphism (SNPs), insertions and deletions (InDels) and SSRs (simple sequence repeats) are essential for crop improvement and better utilization in genetic breeding. However, the resources for the sacred lotus (Nelumbo nucifera Gaertn.) are still limited. In the present study, to dissect large-scale genomic molecular marker resources for sacred lotus, we re-sequenced a Thailand sacred lotus cultivar ‘Chiang Mai wild lotus’ and compared with the reported lotus genome ‘Middle lake wild lotus’. A total of 3,180,059 SNPs, 328, 251 InDels and 14,191 SVs were found between the two genomes. The functional impact analyses of these SNPs indicated that they may be involved in metabolic processes, binding, catalytic activity, etc. Mining the genome sequences for SSRs showed that 191,657 SSRs were identified with a frequency of one SSR per 4.23 kb and 103,656 SSR primer pairs were designed. Furthermore, 14, 502 EST-SSRs were also indentified using the available RNA-seq data in the NCBI. A subset of 150 SSRs (genomic and EST-SSRs) was randomly selected for validation and genetic diversity analysis. The genotypes could be easily distinguished using these SSR markers and the ‘Chiang Mai wild lotus’ was obviously differentiated from the other Chinese accessions. This study provides considerable amounts of genomic resources and markers for the quantitative trait locus (QTL) identification and molecular selection of the species, which could have a potential role in various applications in sacred lotus breeding.     

Genome Wide Characterization of Short Tandem Repeat Markers in Sweet Orange (Citrus sinensis)

Sweet orange (Citrus sinensis) is one of the major cultivated and most-consumed citrus species. With the goal of enhancing the genomic resources in citrus, we surveyed, developed and characterized microsatellite markers in the ≈347 Mb sequence assembly of the sweet orange genome. A total of 50,846 SSRs were identified with a frequency of 146.4 SSRs/Mbp. Dinucleotide repeats are the most frequent repeat class and the highest density of SSRs was found in chromosome 4. SSRs are non-randomly distributed in the genome and most of the SSRs (62.02%) are located in the intergenic regions. We found that AT-rich SSRs are more frequent than GC-rich SSRs. A total number of 21,248 SSR primers were successfully developed, which represents 89 SSR markers per Mb of the genome. A subset of 950 developed SSR primer pairs were synthesized and tested by wet lab experiments on a set of 16 citrus accessions. In total we identified 534 (56.21%) polymorphic SSR markers that will be useful in citrus improvement. The number of amplified alleles ranges from 2 to 12 with an average of 4 alleles per marker and an average PIC value of 0.75. The newly developed sweet orange primer sequences, their in silico PCR products, exact position in the genome assembly and putative function are made publicly available. We present the largest number of SSR markers ever developed for a citrus species. Almost two thirds of the markers are transferable to 16 citrus relatives and may be used for constructing a high density linkage map. In addition, they are valuable for marker-assisted selection studies, population structure analyses and comparative genomic studies of C. sinensis with other citrus related species. Altogether, these markers provide a significant contribution to the citrus research community.     

A pipeline for effectively developing highly polymorphic simple sequence repeats markers based on multi‐sample genomic data

Simple sequence repeats (SSRs) are widely used genetic markers in ecology, evolution, and conservation even in the genomics era, while a general limitation to their application is the difficulty of developing polymorphic SSR markers. Next‐generation sequencing (NGS) offers the opportunity for the rapid development of SSRs; however, previous studies developing SSRs using genomic data from only one individual need redundant experiments to test the polymorphisms of SSRs. In this study, we designed a pipeline for the rapid development of polymorphic SSR markers from multi‐sample genomic data. We used bioinformatic software to genotype multiple individuals using resequencing data, detected highly polymorphic SSRs prior to experimental validation, significantly improved the efficiency and reduced the experimental effort. The pipeline was successfully applied to a globally threatened species, the brown eared‐pheasant (Crossoptilon mantchuricum), which showed very low genomic diversity. The 20 newly developed SSR markers were highly polymorphic, the average number of alleles was much higher than the genomic average. We also evaluated the effect of the number of individuals and sequencing depth on the SSR mining results, and we found that 10 individuals and ~10X sequencing data were enough to obtain a sufficient number of polymorphic SSRs, even for species with low genetic diversity. Furthermore, the genome assembly of NGS data from the optimal number of individuals and sequencing depth can be used as an alternative reference genome if a high‐quality genome is not available. Our pipeline provided a paradigm for the application of NGS technology to mining and developing molecular markers for ecological and evolutionary studies.     

Development and Application of Microsatellites in Candidate Genes Related to Wood Properties in the Chinese White Poplar (Populus tomentosa Carr.)

Gene-derived simple sequence repeats (genic SSRs), also known as functional markers, are often preferred over random genomic markers because they represent variation in gene coding and/or regulatory regions. We characterized 544 genic SSR loci derived from 138 candidate genes involved in wood formation, distributed throughout the genome of Populus tomentosa, a key ecological and cultivated wood production species. Of these SSRs, three-quarters were located in the promoter or intron regions, and dinucleotide (59.7%) and trinucleotide repeat motifs (26.5%) predominated. By screening 15 wild P. tomentosa ecotypes, we identified 188 polymorphic genic SSRs with 861 alleles, 2–7 alleles for each marker. Transferability analysis of 30 random genic SSRs, testing whether these SSRs work in 26 genotypes of five genus Populus sections (outgroup, Salix matsudana), showed that 72% of the SSRs could be amplified in Turanga and 100% could be amplified in Leuce. Based on genotyping of these 26 genotypes, a neighbour-joining analysis showed the expected six phylogenetic groupings. In silico analysis of SSR variation in 220 sequences that are homologous between P. tomentosa and Populus trichocarpa suggested that genic SSR variations between relatives were predominantly affected by repeat motif variations or flanking sequence mutations. Inheritance tests and single-marker associations demonstrated the power of genic SSRs in family-based linkage mapping and candidate gene-based association studies, as well as marker-assisted selection and comparative genomic studies of P. tomentosa and related species.     

Genetic markers in Andean Puya species (Bromeliaceae) with implications on plastome evolution and phylogeny

The Andean plant endemic Puya is a striking example of recent and rapid diversification from central Chile to the northern Andes, tracking mountain uplift. This study generated 12 complete plastomes representing nine Puya species and compared them to five published plastomes for their features, genomic evolution, and phylogeny. The total size of the Puya plastomes ranged from 159,542 to 159,839 bp with 37.3%–37.4% GC content. The Puya plastomes were highly conserved in organization and structure with a typical quadripartite genome structure. Each of the 17 consensus plastomes harbored 133 genes, including 87 protein‐coding genes, 38 tRNA (transfer RNA) genes, and eight rRNA (ribosomal RNA) genes; we found 69–78 tandem repeats, 45–60 SSRs (simple sequence repeats), and 8–22 repeat structures among 13 species. Four protein‐coding genes were identified under positive site‐specific selection in Puya. The complete plastomes and hypervariable regions collectively provided pronounced species discrimination in Puya and a practical tool for future phylogenetic studies. The reconstructed phylogeny and estimated divergence time for the lineage suggest that the diversification of Puya is related to Andean orogeny and Pleistocene climatic oscillations. This study provides plastome resources for species delimitation and novel phylogenetic and biogeographic studies.     

Mathematical and Live Meningococcal Models for Simple Sequence Repeat Dynamics – Coherent Predictions and Observations

Evolvability by means of simple sequence repeat (SSR) instability is a feature under the constant influence of opposing selective pressures to expand and compress the repeat tract and is mechanistically influenced by factors that affect genetic instability. In addition to direct selection for protein expression and structural integrity, other factors that influence tract length evolution were studied. The genetic instability of SSRs that switch the expression of antibiotic resistance ON and OFF was modelled mathematically and monitored in a panel of live meningococcal strains. The mathematical model showed that the SSR length of a theoretical locus in an evolving population may be shaped by direct selection of expression status (ON or OFF), tract length dependent (α) and tract length independent factors (β). According to the model an increase in α drives the evolution towards shorter tracts. An increase in β drives the evolution towards a normal distribution of tract lengths given that an upper and a lower limit are set. Insertion and deletion biases were shown to skew allelic distributions in both directions. The meningococcal SSR model was tested in vivo by monitoring the frequency of spectinomycin resistance OFF→ON switching in a designed locus. The instability of a comprehensive panel of the homopolymeric SSRs, constituted of a range of 5–13 guanine nucleotides, was monitored in wildtype and mismatch repair deficient backgrounds. Both the repeat length itself and mismatch repair deficiency were shown to influence the genetic instability of the homopolymeric tracts. A possible insertion bias was observed in tracts ≤G₁₀. Finally, an inverse correlation between the number of tract-encoded amino acids and growth in the presence of ON-selection illustrated a limitation to SSR expansion in an essential gene associated with the designed model locus and the protein function mediating antibiotic resistance.     

The complete chloroplast genome sequence of <Emphasis Type="Italic">Dodonaea viscosa</Emphasis>: comparative and phylogenetic analyses

The plant chloroplast (cp) genome is a highly conserved structure which is beneficial for evolution and systematic research. Currently, numerous complete cp genome sequences have been reported due to high throughput sequencing technology. However, there is no complete chloroplast genome of genus Dodonaea that has been reported before. To better understand the molecular basis of Dodonaea viscosa chloroplast, we used Illumina sequencing technology to sequence its complete genome. The whole length of the cp genome is 159,375 base pairs (bp), with a pair of inverted repeats (IRs) of 27,099 bp separated by a large single copy (LSC) 87,204 bp, and small single copy (SSC) 17,972 bp. The annotation analysis revealed a total of 115 unique genes of which 81 were protein coding, 30 tRNA, and four ribosomal RNA genes. Comparative genome analysis with other closely related Sapindaceae members showed conserved gene order in the inverted and single copy regions. Phylogenetic analysis clustered D. viscosa with other species of Sapindaceae with strong bootstrap support. Finally, a total of 249 SSRs were detected. Moreover, a comparison of the synonymous (Ks) and nonsynonymous (Ka) substitution rates in D. viscosa showed very low values. The availability of cp genome reported here provides a valuable genetic resource for comprehensive further studies in genetic variation, taxonomy and phylogenetic evolution of Sapindaceae family. In addition, SSR markers detected will be used in further phylogeographic and population structure studies of the species in this genus.     

Genome-Wide Characterization of Simple Sequence Repeat (SSR) Loci in Chinese Jujube and Jujube SSR Primer Transferability

Chinese jujube (Ziziphus jujuba), an economically important species in the Rhamnaceae family, is a popular fruit tree in Asia. Here, we surveyed and characterized simple sequence repeats (SSRs) in the jujube genome. A total of 436,676 SSR loci were identified, with an average distance of 0.93 Kb between the loci. A large proportion of the SSRs included mononucleotide, dinucleotide and trinucleotide repeat motifs, which accounted for 64.87%, 24.40%, and 8.74% of all repeats, respectively. Among the mononucleotide repeats, A/T was the most common, whereas AT/TA was the most common dinucleotide repeat. A total of 30,565 primer pairs were successfully designed and screened using a series of criteria. Moreover, 725 of 1,000 randomly selected primer pairs were effective among 6 cultivars, and 511 of these primer pairs were polymorphic. Sequencing the amplicons of two SSRs across three jujube cultivars revealed variations in the repeats. The transferability of jujube SSR primers proved that 35/64 SSRs could be transferred across family boundary. Using jujube SSR primers, clustering analysis results from 15 species were highly consistent with the Angiosperm Phylogeny Group (APGIII) System. The genome-wide characterization of SSRs in Chinese jujube is very valuable for whole-genome characterization and marker-assisted selection in jujube breeding. In addition, the transferability of jujube SSR primers could provide a solid foundation for their further utilization.     

Comparative analyses of simple sequence repeats (SSRs) in 23 mosquito species genomes: Identification,characterization and distribution (Diptera: Culicidae)

Simple sequence repeats (SSRs) exist in both eukaryotic and prokaryotic genomes and are the most popular genetic markers, but the SSRs of mosquito genomes are still not well understood. In this study, we identified and analyzed the SSRs in 23 mosquito species using Drosophila melanogaster as reference at the whole-genome level. The results show that SSR numbers (33 076-560 175/genome) and genome sizes (574.57-1342.21 Mb) are significantly positively correlated (R~= 0.8992, P < 0.01), but the correlation in individual species varies in these mosquito species. In six types of SSR, mono- to trinucleotide SSRs are dominant with cumulative percentages of 95.14%-99.00% and densities of 195.65/Mb-787.51/Mb, whereas tetra- to hexanucleotide SSRs are rare with 1.12%-4.22% and 3.76/Mb-40.23/Mb. The (A/T)n,(AC/GT)n and (AGC/GCT)n are the most frequent motifs in mononucleotide, dinucleotide and trinucleotide SSRs, respectively, and the motif frequencies of tetra- to hexanucleotide SSRs appear to be species-specific. The 10-20 bp length of SSRs are dominant with the number of 11() 561 ± 93 482 and the frequency of 87.25%± 5.73% on average, and the number and frequency decline with the increase oflength. Most SSRs(83.34%± 7.72%) are located in intergenic regions, followed by intron regions (11.59%± 5.59%), exon regions (3.74%± 1.95%), and untranslated regions (1.32%± 1.39%). The mono-, di- and trinucleotide SSRs are the main SSRs in both gene regions (98.55%± 0.85%) and exon regions (99.27%± 0.52%). An average of 42.52% of total genes contains SSRs, and the preference for SSR occurrenee in different gene subcategories are species-specific. The study provides useful insights into the SSR diversity, characteristics and distribution in 23 mosquito species of genomes.     

Genome-Wide Comparative Analyses of Microsatellites in Papaya

Microsatellites, or simple sequence repeats (SSRs), are highly polymorphic and universally distributed in eukaryotes. SSRs have been used extensively as sequence tagged markers in genetic studies. Recently, the functional and evolutionary importance of SSRs has received considerable attention. Here we report the mining and characterization of the SSRs in papaya genome. We analyzed SSRs from 277.4 Mb of whole genome shotgun (WGS) sequences, 51.2 Mb bacterial artificial chromosome (BAC) end sequences (BES), and 13.4 Mb expressed sequence tag (EST) sequences. The papaya SSR density was one SSR per 0.7 kb of DNA sequence in the WGS, which was higher than that in BES and EST sequences. SSR abundance was dramatically reduced as the repeat length increased. According to SSR motif length, dinucleotide repeats were the most common motif in class I, whereas hexanucleotides were the most copious in class II SSRs. The tri- and hexanucleotide repeats of both classes were greater in EST sequences compared to genomic sequences. In class I SSR, AT and AAT were the most frequent motifs in BES and WGS sequences. By contrast, AG and AAG were the most abundant in EST sequences. For SSR marker development, 9,860 primer pairs were surveyed for amplification and polymorphism. Successful amplification and polymorphic rates were 66.6% and 17.6%, respectively. The highest polymorphic rates were achieved by AT, AG, and ATG motifs. The genome wide analysis of microsatellites revealed their frequency and distribution in papaya genome, which varies among plant genomes. This complete set of SSRs markers throughout the genome will assist diverse genetic studies in papaya and related species.     

Complete chloroplast genome sequences of Dipterygium glaucum and Cleome chrysantha and other Cleomaceae Species,comparative analysis and phylogenetic relationships

This current study presents, for the first time, the complete chloroplast genome of two Cleomaceae species: Dipterygium glaucum and Cleome chrysantha in order to evaluate the evolutionary relationship. The cp genome is 158,576 bp in length with 35.74% GC content in D. glaucum and 158,111 bp with 35.96% GC in C. chrysantha. Inverted repeats IR 26,209 bp, 26,251 bp each, LSC of 87,738 bp, 87,184 bp and SSC of 18,420 bp, 18,425 bp respectively. There are 136 genes in the genome, which includes 80 protein coding genes, 31 tRNA genes and four rRNA genes were observed in both chloroplast genomes. 117 genes are unique while the remaining 19 genes are duplicated in IR regions. The analysis of repeats shows that the cp genome includes all types of repeats with more frequent occurrences of palindromic; Also, this analysis indicates that the total number of simple sequence repeats (SSR) were 323 in D. glaucum, and 313 in C. chrysantha, of which the majority of the SSRs in these plastid genomes were mononucleotide repeats A/T which are located in the intergenic spacer. Moreover, the comparative analysis of the four cp sequences revealed four hotspot genes (atpF, rpoC2, rps19, and ycf1), these variable regions could be used as molecular makers for the species authentication as well as resources for inferring phylogenetic relationships of the species. All the relationships in the phylogenetic tree are with high support, this indicate that the complete chloroplast genome is a useful data for inferring phylogenetic relationship within the Cleomaceae and other families. The simple sequence repeats identified will be useful for identification, genetic diversity, and other evolutionary studies of the species. This study reported the first cp genome of the genus Dipterygium and Cleome. The finding of this study will be beneficial for biological disciplines such as evolutionary and genetic diversity studies of the species within the core Cleomaceae.     

Genome-Wide Comparative Analysis of Microsatellites in Pineapple

Pineapple (Ananas comosus (L.) Merrill) is the second most important tropical fruit in term of international trade. The availability of whole genomic sequences and expressed sequence tags (ESTs) offers an opportunity to identify and characterize microsatellite or simple sequence repeat (SSR) markers in pineapple. A total of 278,245 SSRs and 41,962 SSRs with an overall density of 728.57 SSRs/Mb and 619.37 SSRs/Mb were mined from genomic and ESTs sequences, respectively. 5′-untranslated regions (5′-UTRs) had the greatest amount of SSRs, 3.6–5.2 fold higher SSR density than other regions. For repeat length, 12 bp was the predominant repeat length in both assembled genome and ESTs. Class I SSRs were underrepresented compared with class II SSRs. For motif length, dinucleotide repeats were the most abundant in genomic sequences, whereas trinucleotides were the most common motif in ESTs. Tri- and hexanucleotides of total SSRs were more prevalent in ESTs than in the whole genome. The SSR frequency decreased dramatically as repeat times increased. AT was the most frequent single motif across the entire genome while AG was the most abundant motif in ESTs. Across six examined plant species, the pineapple genome displayed the highest density, substantially more than the second-place cucumber. Annotation and expression analyses were also conducted for genes containing SSRs. This thorough analysis of SSR markers in pineapple provided valuable information on the frequency and distribution of SSRs in the pineapple genome. This genomic resource will expedite genomic research and pineapple improvement.     

Development of genomic simple sequence repeat markers in opium poppy by next-generation sequencing

Opium poppy (Papaver somniferum L.) is an important pharmaceutical crop with very few genetic marker resources. To expand these resources, we sequenced genomic DNA using pyrosequencing technology and examined the DNA sequences for simple sequence repeats (SSRs). A total of 1,244,412 sequence reads were obtained covering 474 Mb. Approximately half of the reads (52 %) were assembled into 166,724 contigs representing 105 Mb of the opium poppy genome. A total of 23,283 non-redundant SSRs were identified in 18,944 contigs (11.3 % of total contigs). Trinucleotide and tetranucleotide repeats were the most abundant SSR repeats, accounting for 49.0 and 27.9 % of all SSRs, respectively. The AAG/TTC repeat was the most abundant trinucleotide repeat, representing 19.7 % of trinucleotide repeats. Other SSR repeat types were AT-rich. A total of 23,126 primer pairs (98.7 % of total SSRs) were designed to amplify SSRs. Fifty-three genomic SSR markers were tested in 37 opium poppy accessions and seven Papaver species for determination of polymorphism and transferability. Intraspecific polymorphism information content (PIC) values of the genomic SSR markers were intermediate, with an average 0.17, while the interspecific average PIC value was slightly higher, 0.19. All markers showed at least 88 % transferability among related species. This study increases sequence coverage of the opium poppy genome by sevenfold and the number of opium poppy-specific SSR markers by sixfold. This is the first report of the development of genomic SSR markers in opium poppy, and the genomic SSR markers developed in this study will be useful in diversity, identification, mapping and breeding studies in opium poppy.     

Whole genome survey and microsatellite motif identification of Artemia franciscana

Artemia is an industrially important genus used in aquaculture as a nutritious diet for fish and as an aquatic model organism for toxicity tests. However, despite the significance of Artemia, genomic research remains incomplete and knowledge on its genomic characteristics is insufficient. In particular, Artemia franciscana of North America has been widely used in fisheries of other continents, resulting in invasion of native species. Therefore, studies on population genetics and molecular marker development as well as morphological analyses are required to investigate its population structure and to discriminate closely related species. Here, we used the Illumina Hi-Seq platform to estimate the genomic characteristics of A. franciscana through genome survey sequencing (GSS). Further, simple sequence repeat (SSR) loci were identified for microsatellite marker development. The predicted genome size was ∼867 Mb using K-mer (a sequence of k characters in a string) analysis (K = 17), and heterozygosity and duplication rates were 0.655 and 0.809%, respectively. A total of 421467 SSRs were identified from the genome survey assembly, most of which were dinucleotide motifs with a frequency of 77.22%. The present study will be a useful basis in genomic and genetic research for A. franciscana.     

Complete chloroplast genome of Myracrodruon urundeuva and its phylogenetics relationships in Anacardiaceae family

Continuous exploratory use of tree species is threatening the existence of several plants in South America. One of these threatened species is Myracroduron urundeuva, highly exploited due to the high quality and durability of its wood. The chloroplast (cp) has been used for several evolutionary studies as well traceability of timber origin, based on its gene sequences and simple sequence repeats (SSR) variability. Cp genome organization is usually consisting of a large single copy and a small single copy region separated by two inverted repeats regions. We sequenced the complete cp genome from M. urundeuva based on Illumina next-generation sequencing. Our results show that the cp genome is 159,883 bp in size. The 36 SSR identified ranging from mono- to hexanucleotides. Positive selection analysis revealed nine genes related to photosystem, protein synthesis, and DNA replication, and protease are under positive selection. Genome comparison a other Anacardiaceae chloroplast genomes showed great variability in the family. The phylogenetic analysis using complete chloroplast genome sequences of other Anacardiaceae family members showed a close relationship with two other economically important genera, Pistacia and Rhus. These results will help future investigations of timber monitoring and population and evolutionary studies. Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00989-1.