Project description:Abstract Wild loquats (Eriobotrya japonica Lindl.) provide remarkable genetic resources for studying domestication and breeding improved varieties. Herein, we generate the first high-quality chromosome-level genome assembly of wild loquat, with 45 791 predicted protein-coding genes. Analysis of comparative genomics indicated that loquat shares a common ancestor with apple and pear, and a recent whole-genome duplication event occurred in loquat prior to its divergence. Genome resequencing showed that the loquat germplasms can be distinctly classified into wild and cultivated groups, and the commercial cultivars have experienced allelic admixture. Compared with cultivated loquats, the wild loquat genome showed very few selected genomic regions and had higher levels of genetic diversity. However, whole-genome scans of selective sweeps were mainly related to fruit quality, size, and flesh color during the domestication process. Large-scale transcriptome and metabolome analyses were further performed to identify differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in wild and cultivated loquats at various fruit development stages. Unlike those in wild loquat, the key DEGs and DAMs involved in carbohydrate metabolism, plant hormone signal transduction, flavonoid biosynthesis, and carotenoid biosynthesis were significantly regulated in cultivated loquats during fruit development. These high-quality reference genome, resequencing, and large-scale transcriptome/metabolome data provide valuable resources for elucidating fruit domestication and molecular breeding in loquat.
Project description:Valencia orange (Citrus sinensis Osbeck), namely summer orange (SO), is a type of late-ripening sweet oranges, the ripening time of which is 4 to 5 months later than that of the middle-ripening common sweet orange (CO). The mastication of SO fruit pulp is worse than that of CO. To date, how the late-ripening and poor pulp mastication traits were domesticated in SO is unknown. In this study, 13 SO cultivars and 12 CO cultivars were used for whole-genome resequencing. Population genetic diversity analysis divided these 25 samples into SO and CO subgroups, respectively. There were 144 and 141 genes identified by selective sweep analysis to be strongly selected during SO and CO evolutionary processes, respectively. Based on gene functional annotation and pathway enrichment analysis, most of these selected genes in SO were related to resistance and lignin biosynthesis. Simultaneously, we comparatively analyzed the transcriptome profiles of the peel and pulp tissues among three SO cultivars and three CO cultivars, which also revealed the difference of lignin synthesis between SO and CO fruits. Moreover, according to the comparative analysis of the lignin content and the expressions of the genes related to lignin biosynthesis in SO and CO fruits, we suggested that lignin may play an important role in the pulp mastication trait of SO. In addition, a SNP molecular marker was developed to distinguish SO and CO. This study reveals that the mastication trait may be formed in the process of SO domestication, while the late-ripening trait may be formed in a genetic mutation event.
Project description:Spinach is a nutritious leafy vegetable belonging to the family Chenopodiaceae. Here we report a high-quality chromosome-scale reference genome assembly of spinach and genome resequencing of 305 cultivated and wild spinach accessions. Reconstruction of ancestral Chenopodiaceae karyotype indicates substantial genome rearrangements in spinach after its divergence from ancestral Chenopodiaceae, coinciding with high repeat content in the spinach genome. Population genomic analyses provide insights into spinach genetic diversity and population differentiation. Genome-wide association studies of 20 agronomical traits identify numerous significantly associated regions and candidate genes for these traits. Domestication sweeps in the spinach genome are identified, some of which are associated with important traits (e.g., leaf phenotype, bolting and flowering), demonstrating the role of artificial selection in shaping spinach phenotypic evolution. This study provides not only insights into the spinach evolution and domestication but also valuable resources for facilitating spinach breeding.
Project description:Sapindus mukorossi is an environmentally friendly plant and renewable energy source whose fruit has been widely used for biomedicine, biodiesel, and biological chemicals due to its richness in saponin and oil contents. Here, we report the first chromosome-scale genome assembly of S. mukorossi (covering ~391 Mb with a scaffold N50 of 24.66 Mb) and characterize its genetic architecture and evolution by resequencing 104 S. mukorossi accessions. Population genetic analyses showed that genetic diversity in the southwestern distribution area was relatively higher than that in the northeastern distribution area. Gene flow events indicated that southwest species may be the donor population for the distribution areas in China. Genome-wide selective sweep analysis showed that a large number of genes are involved in defense responses, growth and development, including SmRPS2, SmRPS4, SmRPS7, SmNAC2, SmNAC23, SmNAC102, SmWRKY6, SmWRKY26, and SmWRKY33. We also identified several candidate genes controlling six agronomic traits by genome-wide association studies, including SmPCBP2, SmbHLH1, SmCSLD1, SmPP2C, SmLRR-RKs, and SmAHP. Our study not only provides a rich genomic resource for further basic research on Sapindaceae woody trees but also identifies several economically significant genes for genomics-enabled improvements in molecular breeding.
Project description: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.
Project description:Eggplant (Solanum melongena L.) is an important horticultural crop and one of the most widely grown vegetables from the Solanaceae family. It was domesticated from a wild, prickly progenitor carrying small, round, non-anthocyanic fruits. We obtained a novel, highly contiguous genome assembly of the eggplant '67/3' reference line, by Hi-C retrofitting of a previously released short read- and optical mapping-based assembly. The sizes of the 12 chromosomes and the fraction of anchored genes in the improved assembly were comparable to those of a chromosome-level assembly. We resequenced 23 accessions of S. melongena representative of the worldwide phenotypic, geographic, and genetic diversity of the species, and one each from the closely related species Solanum insanum and Solanum incanum. The eggplant pan-genome contained approximately 51.5 additional megabases and 816 additional genes compared with the reference genome, while the pan-plastome showed little genetic variation. We identified 53 selective sweeps related to fruit color, prickliness, and fruit shape in the nuclear genome, highlighting selection leading to the emergence of present-day S. melongena cultivars from its wild ancestors. Candidate genes underlying the selective sweeps included a MYBL1 repressor and CHALCONE ISOMERASE (for fruit color), homologs of Arabidopsis GLABRA1 and GLABROUS INFLORESCENCE STEMS2 (for prickliness), and orthologs of tomato FW2.2, OVATE, LOCULE NUMBER/WUSCHEL, SUPPRESSOR OF OVATE, and CELL SIZE REGULATOR (for fruit size/shape), further suggesting that selection for the latter trait relied on a common set of orthologous genes in tomato and eggplant.
Project description:Populus cathayana Rehder, an indigenous poplar species of ecological and economic importance, is widely distributed in a high-elevation range from southwest to northeast China. Further development of this species as a sustainable poplar resource has been hindered by a lack of genome information the at the population level. Here, we produced a chromosome-level genome assembly of P. cathayana, covering 406.55 Mb (scaffold N50 = 20.86 Mb) and consisting of 19 chromosomes, with 35 977 protein-coding genes. Subsequently, we made a genomic variation atlas of 438 wild individuals covering 36 representative geographic areas of P. cathayana, which were divided into four geographic groups. It was inferred that the Northwest China regions served as the genetic diversity centers and a population bottleneck happened during the history of P. cathayana. By genotype-environment association analysis, 947 environment-association loci were significantly associated with temperature, solar radiation, precipitation, and altitude variables. We identified local adaptation genes involved in DNA repair and UV radiation response, among which UVR8, HY5, and CUL4 had key roles in high-altitude adaptation of P. cathayana. Predictions of adaptive potential under future climate conditions showed that P. cathayana populations in areas with drastic climate change were anticipated to have greater maladaptation risk. These results provide comprehensive insights for understanding wild poplar evolution and optimizing adaptive potential in molecular breeding.
Project description:Sperm DNA methylation is crucial for fertility and viability of offspring but epigenome evolution in mammals is largely understudied. By comparing sperm DNA methylomes and large-scale genome-wide association study (GWAS) signals between human and cattle, we aimed to examine the DNA methylome evolution and its associations with complex phenotypes in mammals. Our analysis revealed that genes with conserved non-methylated promoters (e.g., ANKS1A and WNT7A) among human and cattle were involved in common system and embryo development, and enriched for GWAS signals of body conformation traits in both species, while genes with conserved hypermethylated promoters (e.g., TCAP and CD80) were engaged in immune responses and highlighted by immune-related traits. On the other hand, genes with human-specific hypomethylated promoters (e.g., FOXP2 and HYDIN) were engaged in neuron system development and enriched for GWAS signals of brain-related traits, while genes with cattle-specific hypomethylated promoters (e.g., LDHB and DGAT2) mainly participated in lipid storage and metabolism. We validated our findings using sperm-retained nucleosome, preimplantation transcriptome, and adult tissue transcriptome data, as well as sequence evolutionary features, including motif binding sites, mutation rates, recombination rates and evolution signatures. In conclusion, our results demonstrate important roles of epigenome evolution in shaping the genetic architecture underlying complex phenotypes, hence enhance signal prioritization in GWAS and provide valuable information for human neurological disorders and livestock genetic improvement.
Project description:As the largest known tree-borne fruit in the world, jackfruit (Artocarpus heterophyllus) is an important cultivated crop in tropical regions of South and Southeast Asia. The species has been cultivated in China for more than 1000 years, but the history of its introduction to the country remains unclear. We assembled a high-quality chromosome-level genome of jackfruit into 985.63 Mb with scaffold N50 of 32.81 Mb. We analyzed whole-genome resequencing data of 295 landraces to investigate the domestication history in China and agronomic trait evolution of jackfruit. Population structure analysis revealed that jackfruits of China could be traced back to originate from Southeast Asia and South Asia independently. Selection signals between jackfruit and its edible congener, cempedak (Artocarpus integer), revealed several important candidate genes associated with fruit development and ripening. Moreover, analyses of selective sweeps and gene expression revealed that the AhePG1 gene may be the major factor in determining fruit texture. This study not only resolves the origins of jackfruit of China, but also provides valuable genomic resources for jackfruit breeding improvement and offers insights into fruit size evolution and fruit texture changes.