High-quality reference genomes of swallowtail butterflies provide insights into their coloration evolution

Swallowtail butterflies(Papilionidae)are a historically significant butterfly group due to their colorful wing patterns,extensive morphological diversity,and phylogenetically important position as a sister group to all other butterflies and have been widely studied regarding ecological adaption,phylogeny,genetics,and evolution.Notably,they contain a unique class of pigments,i.e.,papiliochromes,which contribute to their color diversity and various biological functions such as predator avoidance and mate preference.To date,however,the genomic and genetic basis of their color diversity and papiliochrome origin in a phylogenetic and evolutionary context remain largely unknown.Here,we obtained high-quality reference genomes of 11 swallowtail butterfly species covering all tribes of Papilioninae and Parnassiinae using long-read sequencing technology.Combined with previously published butterfly genomes,we obtained robust phylogenetic relationships among tribes,overcoming the challenges of incomplete lineage sorting(ILS)and gene flow.Comprehensive genomic analyses indicated that the evolution of Papilionidae-specific conserved non-exonic elements(PSCNEs)and transcription factor binding sites(TFBSs)of patterning and transporter/cofactor genes,together with the rapid evolution of transporters/cofactors,likely promoted the origin and evolution of papiliochromes.These findings not only provide novel insights into the genomic basis of color diversity,especially papiliochrome origin in swallowtail butterflies,but also provide important data resources for exploring the evolution,ecology,and conservation of butterflies.

The pineapple reference genome:Telomere-to-telomere assembly, manually curated annotation, and comparative analysis

Pineapple is the third most crucial tropical fruit worldwide and available in five varieties.Genomes of different pineapple varieties have been released to date;however,none of them are complete,with all exhibiting substantial gaps and representing only two of the five pineapple varieties.This significantly hinders the advancement of pineapple breeding efforts.In this study,we sequenced the genomes of three varieties:a wild pineapple variety,a fiber pineapple variety,and a globally cultivated edible pineapple variety.We constructed the first gap-free reference genome(Ref)for pineapple.By consolidating multiple sources of evidence and manually revising each gene structure annotation,we identified 26,656 proteincoding genes.The BUSCO evaluation indicated a completeness of 99.2%,demonstrating the high quality of the gene structure annotations in this genome.Utilizing these resources,we identified 7,209 structural variations across the three varieties.Approximately 30.8%of pineapple genes were located within±5 kb of structural variations,including 30 genes associated with anthocyanin synthesis.Further analysis and functional experiments demonstrated that the high expression of AcMYB528 aligns with the accumulation of anthocyanins in the leaves,both of which may be affected by a 1.9-kb insertion fragment.In addition,we developed the Ananas Genome Database,which offers data browsing,retrieval,analysis,and download functions.The construction of this database addresses the lack of pineapple genome resource databases.In summary,we acquired a seamless pineapple reference genome with highquality gene structure annotations,providing a solid foundation for pineapple genomics and a valuable reference for pineapple breeding.

Extensive sequence divergence between the reference genomes of Taraxacum kok-saghyz and Taraxacum mongolicum

Plants belonging to the genus Taraxacum are widespread all over the world,which contain rubber-producing and non-rubberproducing species.However,the genomic basis underlying natural rubber(NR)biosynthesis still needs more investigation.Here,we presented high-quality genome assemblies of rubber-producing T.kok-saghyz TK1151 and non-rubber-producing T.mongolicum TM5.Comparative analyses uncovered a large number of genetic variations,including inversions,translocations,presence/absence variations,as well as considerable protein divergences between the two species.Two gene duplication events were found in these two Taraxacum species,including one common ancestral whole-genome triplication and one subsequent round of gene amplification.In genomes of both TK1151 and TM5,we identified the genes encoding for each step in the NR biosynthesis pathway and found that the SRPP and CPT gene families have experienced a more obvious expansion in TK1151 compared to TM5.This study will have large-ranging implications for the mechanism of NR biosynthesis and genetic improvement of NR-producing crops.

Integrated tool for microsatellite isolation and validation from the reference genome and their application in the study of breeding turnover in an endangered avian population

Accurate individual identification is required to estimate survival rates in avian populations.For endangered species,non-invasive methods of obtaining individual identification,such as using molted feathers as a source of DNA for microsatellite markers,are preferred because of less disturbance,easy sample preparation and high efficiency.With the availability of many avian genomes,a few pipelines isolating genome-wide microsatellites have been published,but it is still a challenge to isolate microsatellites from the reference genome efficiently.Here,we have developed an integrated tool comprising a bioinformatic pipeline and experimental procedures for microsatellite isolation and validation based on the reference genome.We have identified over 95000 microsatellite loci and established a system comprising 10 highly polymorphic markers(PIC value:0.49–0.93,mean:0.79)for an endangered species,saker falcon(Falco cherrug).These markers(except 1)were successfully amplified in 126 molted feathers,exhibiting high amplification success rates(83.9–99.7%),high quality index(0.90–0.97)and low allelic dropout rates(1–9.5%).To further assess the efficiency of this marker system in a population study,we identified individual sakers using these molted feathers(adult)and 146 plucked feathers(offspring).The use of parent and offspring samples enabled us to infer the genotype of missing samples(N=28),and all adult genotypes were used to ascertain that breeding turnover is a useful proxy for survival estimation in sakers.Our study presents a cost-effective tool for microsatellite isolation based on publicly available reference genomes and demonstrates the power of this tool in estimating key parameters of avian population dynamics.

Genome Size of Alexandrium catenella and Gracilariopsis lemaneiformis Estimated by Flow Cytometry

Flow cytometry(FCM) technique has been widely applied to estimating the genome size of various higher plants. However, there is few report about its application in algae. In this study, an optimized procedure of FCM was exploited to estimate the genome size of two eukaryotic algae. For analyzing Alexandrium catenella, an important red tide species, the whole cell instead of isolated nucleus was studied, and chicken erythrocytes were used as an internal reference. The genome size of A. catenella was estimated to be 56.48 ± 4.14 Gb(1C), approximately nineteen times larger than that of human genome. For analyzing Gracilariopsis lemaneiformis, an important economical red alga, the purified nucleus was employed, and Arabidopsis thaliana and Chondrus crispus were used as internal references, respectively. The genome size of Gp. lemaneiformis was 97.35 ± 2.58 Mb(1C) and 112.73 ± 14.00 Mb(1C), respectively, depending on the different internal references. The results of this research will promote the related studies on the genomics and evolution of these two species.

A chromosome-level genome assembly for Erianthus fulvus provides insights into its biofuel potential and facilitates breeding for improvement of sugarcane

Erianthus produces substantial biomass,exhibits a good Brix value,and shows wide environmental adaptability,making it a potential biofuel plant.In contrast to closely related sorghum and sugarcane,Erianthus can grow in degraded soils,thus releasing pressure on agricultural lands used for biofuel production.However,the lack of genomic resources for Erianthus hinders its genetic improvement,thus limiting its potential for biofuel production.In the present study,we generated a chromosome-scale reference genome for Erianthus fulvus Nees.The genome size estimated by flow cytometry was 937 Mb,and the assembled genome size was 902 Mb,covering 96.26%of the estimated genome size.A total of 35065 proteincoding genes were predicted,and 67.89%of the genome was found to be repetitive.A recent wholegenome duplication occurred approximately 74.10 million years ago in the E.fulvus genome.Phylogenetic analysis showed that E.fulvus is evolutionarily closer to S.spontaneum and diverged after S.bicolor.Three of the 10 chromosomes of E.fulvus formed through rearrangements of ancestral chromosomes.Phylogenetic reconstruction of the Saccharum complex revealed a polyphyletic origin of the complex and a sister relationship of E.fulvus with Saccharum sp.,excluding S.arundinaceum.On the basis of the four amino acid residues that provide substrate specificity,the E.fulvus SWEET proteins were classified as monoand disaccharide sugar transporters.Ortho-QTL genes identified for 10 biofuel-related traits may aid in the rapid screening of E.fulvus populations to enhance breeding programs for improved biofuel production.The results of this study provide valuable insights for breeding programs aimed at improving biofuel production in E.fulvus and enhancing sugarcane introgression programs.

Pistachio genomes provide insights into nut tree domestication and ZW sex chromosome evolution

Pistachio is a nut crop domesticated in the Fertile Crescent and a dioecious species with ZW sex chromosomes.We sequenced the genomes of Pistacia vera cultivar(cv.)Siirt,the female parent,and P.vera cv.Bagyolu,the male parent.Two chromosome-level reference genomes of pistachio were generated,and Z and W chromosomes were assembled.The ZW chromosomes originated from an autosome following the first inversion,which occurred approximately 8.18 Mya.Three inversion events in the W chromosome led to the formation of a 12.7-Mb(22.8%of the W chromosome)non-recombining region.These W-specific sequences contain several genes of interest that may have played a pivotal role in sex determination and contributed to the initiation and evolution of a ZW sex chromosome system in pistachio.The W-specific genes,including defA,defA-like,DYT1,two PTEN1,and two tandem duplications of six VPS13A paralogs,are strong candidates for sex determination or differentiation.Demographic history analysis of resequenced genomes suggest that cultivated pistachio underwent severe domestication bottlenecks approximately 7640 years ago,dating the domestication event close to the archeological record of pistachio domestication in Iran.We identified 390,211,and 290 potential selective sweeps in 3 cultivar subgroups that underlie agronomic traits such as nut development and quality,grafting success,flowering time shift,and drought tolerance.These findings have improved our understanding of the genomic basis of sex determination/differentiation and horticulturally important traits and will accelerate the improvement of pistachio cultivars and rootstocks.

A gap-free genome assembly of Chlamydomonas reinhardtii anddetection of translocations induced by CRISPR-mediated mutagenesis

Genomic assemblies of the unicellular green alga Chlamydomonas reinhardtii have provided important resources for researchers.However,assembly errors,large gaps,and unplaced scaffolds as well as strain-specific variants currently impede many types of analysis.By combining PacBio HiFi and Oxford Nanopore long-read technologies,we generated a de novo genome assembly for strain CC-5816,derived from crosses of strains CC-125 and CC-124.Multiple methods of evaluating genome completeness and base-pair error rate suggest that the final telomere-to-telomere assembly is highly accurate.The CC-5816 assembly enabled previously difficult analyses that include characterization of the 17 centromeres,rDNA arrays on three chromosomes,and 56 insertions of organellar DNA into the nuclear genome.Using Nanopore sequencing,we identified sites of cytosine(CpG)methylation,which are enriched at centromeres.We analyzed CRISPR-Cas9 insertional mutants in the PF23 gene.Two of the three alleles produced progeny that displayed patterns of meiotic inviability that suggested the presence of a chromosomal aberration.Mapping Nanopore reads from pf23-2 and pf23-3 onto the CC-5816 genome showed that these two strains each carry a translocation that was initiated at the PF23 gene locus on chromosome 11 and joined with chromosomes 5 or 3,respectively.The translocations were verified by demonstrating linkage between loci on the two translocated chromosomes in meiotic progeny.The three pf23 alleles display the expected short-cilia phenotype,and immunoblotting showed that pf23-2 lacks the PF23 protein.Our CC-5816 genome assembly will undoubtedly provide an important tool for the Chlamydomonas research community.

A legacy of the “1% program”-The “Chinese Chapter” of the human genome reference sequence

The year of 2018 marks the 65th anniversary of the discovery of DNA double helix and the 15th anniversary of the successful completion of the international Human Genome Project (HGP),the two revolutions in life sciences (Sharp, 2014). The year also sees the effective implementation of the "1%Program", the Chinese contribution to the reference sequence of the human genome,which coincides with the 40th anniversary of the founding of the Genetics Society of China, one of the most influential national academic organizations in China.

Building a sequence map of the pig pan-genome from multiple de novo assemblies and Hi-C data

Pigs were domesticated independently in the Near East and China,indicating that a single reference genome from one individual is unable to represent the full spectrum of divergent sequences in pigs worldwide.Therefore,12 de novo pig assemblies from Eurasia were compared in this study to identify the missing sequences from the reference genome.As a result,72.5 Mb of nonredundant sequences(~3% of the genome)were found to be absent from the reference genome(Sscrofa11.1)and were defined as pan-sequences.Of the pan-sequences,9.0 Mb were dominant in Chinese pigs,in contrast with their low frequency in European pigs.One sequence dominant in Chinese pigs contained the complete genic region of the tazarotene-induced gene 3(TIG3)gene which is involved in fatty acid metabolism.Using flanking sequences and Hi-C based methods,27.7% of the sequences could be anchored to the reference genome.The supplementation of these sequences could contribute to the accurate interpretation of the 3D chromatin structure.A web-based pan-genome database was further provided to serve as a primary resource for exploration of genetic diversity and promote pig breeding and biomedical research.