Combined genomic, transcriptomic, and metabolomic an alyses provide in sights into chayote (Sechium edule) evolution and fruit development

Chayote(Sechium edule)is an agricultural crop in the Cucurbitaceae family that is rich in bioactive components.To enhance genetic research on chayote,we used Nanopore third-generation sequencing combined with Hi-C data to assemble a draft chayote genome.A chromosome-level assembly anchored on 14 chromosomes(N50 contig and scaffold sizes of 8.40 and 46.56 Mb,respectively)estimated the genome size as 606.42 Mb,which is large for the Cucurbitaceae,with 65.94%(401.08 Mb)ofthe genome comprising repetitive sequences;28,237 protein-coding genes were predicted.Comparative genome analysis indicated that chayote and snake gourd diverged from sponge gourd and that a whole-genome duplication(WGD)event occurred in chayote at 25±4 Mya.Transcriptional and metabolic analysis revealed genes involved in fruit texture,pigment,fl avor,fl avonoids,antioxidants,and plant hormones during chayote fruit development.The analysis of the genome,transcriptome,and metabolome provides insights into chayote evolution and lays the groundwork for future research on fruit and tuber development and genetic improvements in chayote.

Genetic relationship and pedigree of Chinese watermelon varieties based on diversity of perfect SNPs

Watermelon(Citrullus lanatus)is one of the world’s most important fruit crops,and China produces the most watermelons in the world.Recently,a watermelon variome consisting of 414 key resequenced accessions was reported.However,the genetic relationships and pedigree of Chinese watermelon varieties in the seed market remain unclear.In this study,241 evenly distributed perfect single nucleotide polymorphisms(SNPs)derived from the watermelon variome were selected for variety identification.The diversity of 247 Chinese watermelon varieties was identified based on their SNP genotypes.The 247 watermelon varieties were clustered into five subpopulations:the East Asian ecotype,intermediate ecotype,small fruit with red flesh ecotype,small fruit with yellow flesh ecotype,and American ecotype.We further established the pedigree of four subpopulations,of which JingXinNo.1,ZaoChunHongYu,HuangXiaoYu and XiaoLan,and Sugarlee were the main doner of the East Asian ecotype,small fruit with red flesh ecotype,small fruit with yellow flesh ecotype,and American ecotype,respectively.Thirty-two core SNPs were selected and applied in watermelon variety identification.They were also validated by the Kompetitive allele-specific PCR(KASPar)platform.The present study furthered our understanding of the genetic relationships and pedigree of watermelon varieties in China,and will help to manage the plant variety protection in watermelon.

Comparison of DUS testing and SNP fingerprinting for variety identification in cucumber

Variety identification plays an important role in protecting the intellectual property of varieties,ensuring seed quality,and encouraging breeding innovation.Currently,morphological evaluation in the field,such as distinctness,uniformity,and stability(DUS)testing,and DNA fingerprinting in the laboratory using molecular markers are two dominant methods used for variety identification.Few studies have compared the results of these approaches,and the relationship between the two methods is obscure.In this study,134 dominant cucumber varieties were evaluated using 50 DUS testing traits and genotyped by 40 single nucleotide polymorphisms(SNPs).The 40 SNPs were developed in our previous study and arewell suited for variety identification.In the DUS testing,significant positive or negative correlations among 50 DUS traits were observed,and 20 core traits,including 15 fruit traits,were further selected to increase field inspection efficiency.This suggested that fruit shape plays an important role in variety identification.The ratio of fruit length/diameter was themost important trait,explaining 9.2%of the phenotypic variation.In the DNA fingerprinting test,the 40 SNPs were highly polymorphic and could distinguish all of the 134 cucumber varieties,and 14 core SNPs were selected to improve the identification rate.Interestingly,the population structure analysis of 134 cucumber varieties by phenotypic data in the DUS test was in accordance with the genotypic data from the DNA fingerprinting,indicating that all varieties could be divided into the same four subgroups:European type,North China type,South China type,and hybrids of the North China and South China types.Moreover,linear correlativity of distinguishment for each pair of varieties was observed between the DUS test and the DNA fingerprinting.These results indicated that these two methods have good application in future research,especially for the scaled-up analysis of hundreds of varieties.

Molecularly tagged genes and quantitative trait loci in cucumber with recommendations for QTL nomenclature

Cucumber,Cucumis sativus L.(2n=2x=14),is an important vegetable crop worldwide.It was the first specialty crop with a publicly available draft genome.Its relatively small,diploid genome,short life cycle,and selfcompatible mating system offers advantages for genetic studies.In recent years,significant progress has been made in molecular mapping,and identification of genes and QTL responsible for key phenotypic traits,but a systematic review of the work is lacking.Here,we conducted an extensive literature review on mutants,genes and QTL that have been molecularly mapped or characterized in cucumber.We documented 81 simply inherited trait genes or major-effect QTL that have been cloned or fine mapped.For each gene,detailed information was compiled including chromosome locations,allelic variants and associated polymorphisms,predicted functions,and diagnostic markers that could be used for marker-assisted selection in cucumber breeding.We also documented 322 QTL for 42 quantitative traits,including 109 for disease resistances against seven pathogens.By alignment of these QTL on the latest version of cucumber draft genomes,consensus QTL across multiple studies were inferred,which provided insights into heritable correlations among different traits.Through collaborative efforts among public and private cucumber researchers,we identified 130 quantitative traits and developed a set of recommendations for QTL nomenclature in cucumber.This is the first attempt to systematically summarize,analyze and inventory cucumber mutants,cloned or mapped genes and QTL,which should be a useful resource for the cucurbit research community.

The genome and transcriptome analysis of snake gourd provide insights into its evolution and fruit development and ripening

Snake gourd(Trichosanthes anguina L.),which belongs to the Cucurbitaceae family,is a popular ornamental and food crop species with medicinal value and is grown in many parts of the world.Although progress has been made in its genetic improvement,the organization,composition,and evolution of the snake gourd genome remain largely unknown.Here,we report a high-quality genome assembly for snake gourd,comprising 202 contigs,with a total size of 919.8 Mb and an N50 size of 20.1 Mb.These findings indicate that snake gourd has one of the largest genomes of Cucurbitaceae species sequenced to date.The snake gourd genome assembly harbors 22,874 protein-coding genes and 80.0%of the genome consists of repetitive sequences.Phylogenetic analysis reveals that snake gourd is closely related to sponge gourd but diverged from their common ancestor~33–47 million years ago.The genome sequence reported here serves as a valuable resource for snake gourd genetic research and comparative genomic studies in Cucurbitaceae and other plant species.In addition,fruit transcriptome analysis reveals the candidate genes related to quality traits during snake gourd fruit development and provides a basis for future research on snake gourd fruit development and ripening at the transcript level.

Regulation of pathological blood-brain barrier for intracranial enhanced drug delivery and anti-glioblastoma therapeutics

The blood-brain barrier(BBB)is an essential component in regulating and maintaining the homeostatic microenvironment of the central nervous system(CNS).During the occurrence and development of glioblastoma(GBM),BBB is pathologically destroyed with a marked increase in permeability.Due to the obstruction of the BBB,current strategies for GBM therapeutics still obtain a meager success rate and may lead to systemic toxicity.Moreover,chemotherapy could promote pathological BBB functional restoration,which results in significantly reduced intracerebral transport of therapeutic agents during multiple administrations of GBM and the eventual failure of GBM chemotherapy.The effective delivery of intracerebral drugs still faces severe challenges.However,strategies that regulate the pathological BBB to enhance the transport of therapeutic agents across the barrier may provide new opportunities for the effective and safe treatment of GBM.This article reviews the structure and function of BBB in physiological states,the mechanisms underlying BBB pathological fenestration during the development of GBM,and the therapeutic strategies of GBM based on BBB intervention and medicinal drugs transporting across the BBB.

A Genomic Variation Map Provides Insights into the Genetic Basis of Spring Chinese Cabbage (Brassica rapa ssp.pekinensis)Selection

Chinese cabbage is the most consumed leafy crop in East Asian countries.However,premature bolting induced by continuous low temperatures severely decreases the yield and quality of the Chinese cabbage, and therefore restricts its planting season and geographic distribution.In the past 40years,spring Chinese cabbage with strong winterness has been selected to meet the market demand.Here,we report a genome variation map of Chinese cabbage generated from the resequencing data of 194 geographically diverse accessions of three ecotypes.In-depth analyses of the selection sweeps and genome-wide patterns revealed that spring Chinese cabbage was selected from a specific population of autumn Chinese cabbage around the area of Shandong peninsula in northern China.We identified 23 genomic loci that underwent intensive selection,and further demonstrated by gene expression and haplotype analyses that the incorporation of elite alleles of VERNALISATION INSENTIVE 3.1(BrVIN3.1)and FLOWER LOCUS C 1(BrFLC1)is a determinant genetic source of variation during selection.Moreover,we showed that the quantitative response of BrVIN3.1 to cold due to the sequence variations in the cis elements of the BrVlN3.1 promoter significantly contributes to bolting-time variation in Chinese cabbage.Collectively, our study provides valuable insights into the genetic basis of spring Chinese cabbage selection and will facilitate the breeding of bolting-resistant Varieties by molecular-marker-assisted selection,transgenic or gene editingapproaches.