HortGenome Search Engine, a universal genomic search engine for horticultural crops.

Horticultural crops comprising fruit, vegetable, ornamental, beverage, medicinal and aromatic plants play essential roles in food security and human health, as well as landscaping. With the advances of sequencing technologies, genomes for hundreds of horticultural crops have been deciphered in recent years, providing a basis for understanding gene functions and regulatory networks and for the improvement of horticultural crops. However, these valuable genomic data are scattered in warehouses with various complex searching and displaying strategies, which increases learning and usage costs and makes comparative and functional genomic analyses across different horticultural crops very challenging. To this end, we have developed a lightweight universal search engine, HortGenome Search Engine (HSE; http://hort.moilab.net), which allows for the querying of genes, functional annotations, protein domains, homologs, and other gene-related functional information of more than 500 horticultural crops. In addition, four commonly used tools, including 'BLAST', 'Batch Query', 'Enrichment analysis', and 'Synteny Viewer' have been developed for efficient mining and analysis of these genomic data.

A haplotype-resolved genome assembly of Malus domestica 'Red Fuji'.

The 'Red Fuji' apple (Malus domestica), is one of the most important and popular economic crops worldwide in the fruit industry. Using PacBio HiFi long reads and Hi-C reads, we assembled a high-quality haplotype-resolved genome of 'Red Fuji', with sizes of 668.7 and 668.8 Mb, and N50 sizes of 34.1 and 31.4 Mb. About 97.2% of sequences were anchored in 34 chromosomes. We annotated both haploid genomes, identifying a total of 95,439 protein-coding genes in the two haplotype genomes, with 98% functional annotation. The haplotype-resolved genome of 'Red Fuji' apple stands as a precise benchmark for an array of analyses, such as comparative genomics, transcriptomics, and allelic expression studies. This comprehensive resource is paramount in unraveling variations in allelic expression, advancing quality improvements, and refining breeding efforts.

The chromosome-level genome assembly of the dwarfing apple interstock Malus hybrid 'SH6'.

Malus hybrid 'SH6' (M. honanensis × M. domestica)is a commonly used apple interstock in China, known for its excellent dwarfing characteristics and cold tolerance. In this study, a combined strategy utilizing PacBio HiFi, Hi-C and parental resequencing data were employed to assemble two haploid genomes for 'SH6'. After chromosome anchoring, the final hapH genome size was 596.63 Mb, with a contig N50 of 34.38 Mb. The hapR genome was 649.37 Mb, with a contig N50 of 36.84 Mb. Further analysis predicted that repeated sequences made up 59.69% and 62.52% of the entire genome, respectively. Gene annotations revealed 45,435 genes for hapH and 48,261 genes for hapR. Combined with genomic synteny we suggest that the hapR genome originates from its maternal parent M. domestica cv. Ralls Janet, while the hapH genome comes from its paternal parent, M. honanensis. The assembled genome significantly contributes to the discovery of genes associated with apple dwarfing and the molecular mechanisms governing them.

Genome assembly of autotetraploid Actinidia arguta highlights adaptive evolution and enables dissection of important economic traits.

Actinidia arguta, the most widely distributed Actinidia species and the second cultivated species in the genus, can be distinguished from the currently cultivated Actinidia chinensis on the basis of its small and smooth fruit, rapid softening, and excellent cold tolerance. Adaptive evolution of tetraploid Actinidia species and the genetic basis of their important agronomic traits are still unclear. Here, we generated a chromosome-scale genome assembly of an autotetraploid male A. arguta accession. The genome assembly was 2.77 Gb in length with a contig N50 of 9.97 Mb and was anchored onto 116 pseudo-chromosomes. Resequencing and clustering of 101 geographically representative accessions showed that they could be divided into two geographic groups, Southern and Northern, which first diverged 12.9 million years ago. A. arguta underwent two prominent expansions and one demographic bottleneck from the mid-Pleistocene climate transition to the late Pleistocene. Population genomics studies using paleoclimate data enabled us to discern the evolution of the species' adaptation to different historical environments. Three genes (AaCEL1, AaPME1, and AaDOF1) related to flesh softening were identified by multi-omics analysis, and their ability to accelerate flesh softening was verified through transient expression assays. A set of genes that characteristically regulate sexual dimorphism located on the sex chromosome (Chr3) or autosomal chromosomes showed biased expression during stamen or carpel development. This chromosome-level assembly of the autotetraploid A. arguta genome and the genes related to important agronomic traits will facilitate future functional genomics research and improvement of A. arguta.

Chromosomal level genome assemblies of two Malus crabapple cultivars Flame and Royalty.

Malus hybrid 'Flame' and Malus hybrid 'Royalty' are representative ornamental crabapples, rich in flavonoids and serving as the preferred materials for studying the coloration mechanism. We generated two sets of high-quality chromosome-level and haplotype-resolved genome of 'Flame' with sizes of 688.2 Mb and 675.7 Mb, and those of 'Royalty' with sizes of 674.1 Mb and 663.6 Mb, all anchored to 17 chromosomes and with a high BUSCO completeness score nearly 99.0%. A total of 47,833 and 47,307 protein-coding genes were annotated in the two haplotype genomes of 'Flame', and the numbers of 'Royalty' were 46,305 and 46,920 individually. The assembled high-quality genomes offer new resources for studying the origin and adaptive evolution of crabapples and the molecular basis of the accumulation of flavonoids and anthocyanins, facilitating molecular breeding of Malus plants.