Polyploidy events shaped the expansion of transcription factors in Cucurbitaceae and exploitation of genes for tendril development

Cucurbitaceae is one of the most important plant families distributed worldwide. Transcription factors (TFs) regulate plant growth at the transcription level. Here, we performed a systematic analysis of 42 641 TFs from 63 families in 14 Cucurbitaceae and 10 non-cucurbit species. Whole-genome duplication (WGD) was the dominant event type in almost all Cucurbitaceae plants. The TF families were divided into 1 210 orthogroups (OGs), of which, 112 were unique to Cucurbitaceae. Although the loss of several gene families was detected in Cucurbitaceae, the gene families expanded in five species that experienced a WGD event comparing with grape. Our findings revealed that the recent WGD events that had occurred in Cucurbitaceae played important roles in the expansion of most TF families. The functional enrichment analysis of the genes that significantly expanded or contracted uncovered five gene families, AUX/IAA, NAC, NBS, HB, and NF-YB. Finally, we conducted a comprehensive analysis of the TCP gene family and identified 16 tendril-related (TEN) genes in 11 Cucurbitaceae species. Interestingly, the characteristic sequence changed from CNNFYFP to CNNFYLP in the TEN gene (Bhi06M000087) of Benincasa hispida. Furthermore, we identified a new characteristic sequence, YNN, which could be used for TEN gene exploitation in Cucurbitaceae. In conclusion, this study will serve as a reference for studying the relationship between gene family evolution and genome duplication. Moreover, it will provide rich genetic resources for functional Cucurbitaceae studies in the future

The draft genome of watermelon (Citrullus lanatus) and resequencing of 20 diverse accessions

Watermelon, Citrullus lanatus, is an important cucurbit crop grown throughout the world. Here we report a high-quality draft genome sequence of the east Asia watermelon cultivar 97103 (2n = 2 7 = 22) containing 23,440 predicted protein-coding genes. Comparative genomics analysis provided an evolutionary scenario for the origin of the 11 watermelon chromosomes derived from a 7-chromosome paleohexaploid eudicot ancestor. Resequencing of 20 watermelon accessions representing three different C. lanatus subspecies produced numerous haplotypes and identified the extent of genetic diversity and population structure of watermelon germplasm. Genomic regions that were preferentially selected during domestication were identified. Many disease-resistance genes were also found to be lost during domestication. In addition, integrative genomic and transcriptomic analyses yielded important insights into aspects of phloem-based vascular signaling in common between watermelon and cucumber and identified genes crucial to valuable fruit-quality traits, including sugar accumulation and citrulline metabolism

Editorial: Translational research for cucurbit molecular breeding: Traits, markers, and genes

Cucurbits (family Cucurbitaceae) are economically important vegetable crops. Major cucurbits growing globally include cucumber, melon, watermelon, and squash/pumpkin. Other cucurbits like bitter melon, bottle gourd, winter melon, and luffa are popular in many Asian and African countries. The last decade has witnessed a rapid development of genetic and genomics resources including draft genome assemblies, and high-density genetic maps in a dozen cucurbit crops, making it possible to accelerate translational research for cucurbit breeding. This Research Topic is a collection of 21 Original Research articles or Reviews highlighting the achievements and future directions in cucurbit translational research. These articles cover a variety of topics ranging from improvement of the cucurbit genome assemblies to identification and molecular mapping of horticulturally important genes or QTL for horticultural traits, and the use of such knowledge in marker-assisted selection for cucurbit improvement. Major findings from these investigations are summarized below.info:eu-repo/semantics/publishedVersio

Comparative genomics reveals candidate carotenoid pathway regulators of ripening watermelon fruit

BACKGROUND: Many fruits, including watermelon, are proficient in carotenoid accumulation during ripening. While most genes encoding steps in the carotenoid biosynthetic pathway have been cloned, few transcriptional regulators of these genes have been defined to date. Here we describe the identification of a set of putative carotenoid-related transcription factors resulting from fresh watermelon carotenoid and transcriptome analysis during fruit development and ripening. Our goal is to both clarify the expression profiles of carotenoid pathway genes and to identify candidate regulators and molecular targets for crop improvement. RESULTS: Total carotenoids progressively increased during fruit ripening up to ~55 μg g(-1) fw in red-ripe fruits. Trans-lycopene was the carotenoid that contributed most to this increase. Many of the genes related to carotenoid metabolism displayed changing expression levels during fruit ripening generating a metabolic flux toward carotenoid synthesis. Constitutive low expression of lycopene cyclase genes resulted in lycopene accumulation. RNA-seq expression profiling of watermelon fruit development yielded a set of transcription factors whose expression was correlated with ripening and carotenoid accumulation. Nineteen putative transcription factor genes from watermelon and homologous to tomato carotenoid-associated genes were identified. Among these, six were differentially expressed in the flesh of both species during fruit development and ripening. CONCLUSIONS: Taken together the data suggest that, while the regulation of a common set of metabolic genes likely influences carotenoid synthesis and accumulation in watermelon and tomato fruits during development and ripening, specific and limiting regulators may differ between climacteric and non-climacteric fruits, possibly related to their differential susceptibility to and use of ethylene during ripening

Whole-genome resequencing of Cucurbita pepo morphotypes to discover genomic variants associated with morphology and horticulturally valuable traits

[EN] Cucurbita pepo contains two cultivated subspecies, each of which encompasses four fruit-shape morphotypes (cultivar groups). The Pumpkin, Vegetable Marrow, Cocozelle, and Zucchini Groups are of subsp. pepo and the Acorn, Crookneck, Scallop, and Straightneck Groups are of subsp. ovifera. Recently, a de novo assembly of the C. pepo subsp. pepo Zucchini genome was published, providing insights into its evolution. To expand our knowledge of evolutionary processes within C. pepo and to identify variants associated with particular morphotypes, we performed whole-genome resequencing of seven of these eight C. pepo morphotypes. We report for the first time whole-genome resequencing of the four subsp. pepo (Pumpkin, Vegetable Marrow, Cocozelle, green Zucchini, and yellow Zucchini) morphotypes and three of the subsp. ovifera (Acorn, Crookneck, and Scallop) morphotypes. A high-depth resequencing approach was followed, using the BGISEQ-500 platform that enables the identification of rare variants, with an average of 33.5X. Approximately 94.5% of the clean reads were mapped against the reference Zucchini genome. In total, 3,823,977 high confidence single-nucleotide polymorphisms (SNPs) were identified. Within each accession, SNPs varied from 636,918 in green Zucchini to 2,656,513 in Crookneck, and were distributed homogeneously along the chromosomes. Clear differences between subspecies pepo and ovifera in genetic variation and linkage disequilibrium are highlighted. In fact, comparison between subspecies pepo and ovifera indicated 5710 genes (22.5%) with Fst > 0.80 and 1059 genes (4.1%) with Fst = 1.00 as potential candidate genes that were fixed during the independent evolution and domestication of the two subspecies. Linkage disequilibrium was greater in subsp. ovifera than in subsp. pepo, perhaps reflective of the earlier differentiation of morphotypes within subsp. ovifera. Some morphotype-specific genes have been localized. Our results offer new clues that may provide an improved understanding of the underlying genomic regions involved in the independent evolution and domestication of the two subspecies. Comparisons among SNPs unique to particular subspecies or morphotypes may provide candidate genes responsible for traits of high economic importance.This work has been supported by Hellenic Agricultural Organization (ELGO) Demeter. Furthermore, we thank the Conselleria de Educacio, Investigacio, Cultura i Esport (Generalitat Valenciana) for funding Project Prometeo 2017/078 "Seleccion de Variedades Tradicionales y Desarrollo de Nuevas Variedades de Cucurbitaceas Adaptadas a la Produccion Ecologica". Also, this work was supported by Chiang Mai University.Xanthopoulou, A.; Montero-Pau, J.; Mellidou, I.; Kissoudis, C.; Blanca Postigo, JM.; Picó Sirvent, MB.; Tsaballa, A.... (2019). Whole-genome resequencing of Cucurbita pepo morphotypes to discover genomic variants associated with morphology and horticulturally valuable traits. Horticulture Research. 6:1-17. https://doi.org/10.1038/s41438-019-0176-9S1176Maynard, D. & Paris, H. in The Encyclopedia of Fruits & Nuts (eds Paull, R. E. & Janick, J.) 276–313 (CABI, New Jersey, U.S.A., 2018).Paris, H. S. in Genetics and Genomics of Cucurbitaceae, Grumet, Rebecca, Katzir, Nurit, Garcia-Mas, Jordi (Eds.) 111–154 (Springer, New York, U.S.A., 2016).Whitaker, T. W. & Davis, G. N. Cucurbits (Leonard Hill (Books) Ltd., London, and Interscience Publishers Inc., New York, 1962).Paris, H. S. History of the cultivar-groups of Cucurbita pepo. Hortic. Rev. 25, 71–170 (2001).Paris, H. S. A proposed subspecific classifiaction for Cucurbita pepo. Phytologia (USA) 61, 133–138 (1986).Lira, R., Andres, T. C. & Nee, M. in Systematic and Ecogeographic Studies on Crop Genepools, Vol. 9, 1–115 (International Plant Genetic Resources Institute, Roma, Italia, 1995).Castellanos-Morales, G. Historical biogeography and phylogeny of Cucurbita: insights from ancestral area reconstruction and niche evolution. Mol. Phylogenet. Evol. 128, 38–54 (2018).Paris, H. S., Lebeda, A., Křistkova, E., Andres, T. C. & Nee, M. H. Parallel evolution under domestication and phenotypic differentiation of the cultivated subspecies of Cucurbita pepo (Cucurbitaceae). Econ. Bot. 66, 71–90 (2012).Dong, W., Wu, D., Li, G., Wu, D. & Wang, Z. Next-generation sequencing from bulked segregant analysis identifies a dwarfism gene in watermelon. Sci. Rep. 8, 2908 (2018).Galpaz, N. et al. Deciphering genetic factors that determine melon fruit‐quality traits using RNA‐Seq‐based high‐resolution QTL and eQTL mapping. Plant J. 94, 169–191 (2018).Gur, A. et al. Genome-wide linkage-disequilibrium mapping to the candidate gene level in melon (Cucumis melo). Sci. Rep. 7, 9770 (2017).Blanca, J. et al. Transcriptome characterization and high throughput SSRs and SNPs discovery in Cucurbita pepo (Cucurbitaceae). BMC Genom. 12, 104 (2011).Esteras, C. et al. High-throughput SNP genotyping in Cucurbita pepo for map construction and quantitative trait loci mapping. BMC Genom. 13, 80 (2012).Montero-Pau, J. et al. An SNP-based saturated genetic map and QTL analysis of fruit-related traits in Zucchini using genotyping-by-sequencing. BMC Genom. 18, 94 (2017).Vicente-Dólera, N. et al. First TILLING platform in Cucurbita pepo: a new mutant resource for gene function and crop improvement. PLoS ONE 9, e112743 (2014).Wyatt, L. E., Strickler, S. R., Mueller, L. A. & Mazourek, M. An acorn squash (Cucurbita pepo ssp. ovifera) fruit and seed transcriptome as a resource for the study of fruit traits in Cucurbita. Hortic. Res. 2, 14070 (2015).Xanthopoulou, A. et al. De novo comparative transcriptome analysis of genes involved in fruit morphology of pumpkin cultivars with extreme size difference and development of EST-SSR markers. Gene 622, 50–66 (2017).Montero‐Pau, J. et al. De novo assembly of the zucchini genome reveals a whole‐genome duplication associated with the origin of the Cucurbita genus. Plant Biotechnol. J. 16, 1161–1171 (2018).Garcia-Mas, J. et al. Cloning and mapping of resistance gene homologues in melon. Plant Sci. 161, 165–172 (2001).Xanthopoulou, A. et al. Comparative analysis of genetic diversity in Greek Genebank collection of summer squash (‘Cucurbita pepo’) landraces using start codon targeted (SCoT) polymorphism and ISSR markers. Aust. J. Crop Sci. 9, 14 (2015).Huang, J. et al. A reference human genome dataset of the BGISEQ-500 sequencer. Gigascience 6, gix024 (2017).Natarajan, K. N. et al. Comparative analysis of sequencing technologies for single-cell transcriptomics. Genome Biol. 20, 70 (2019).Li, H. & Durbin, R. Fast and accurate short read alignment with Burrows–Wheeler transform. Bioinformatics 25, 1754–1760 (2009).Tian, L. et al. Transcript and proteomic analysis of developing white lupin (Lupinus albus L.) roots. BMC Plant Biol. 9, 1 (2009).Li, H. et al. The sequence alignment/map format and SAMtools. Bioinformatics 25, 2078–2079 (2009).McKenna, A. et al. The Genome Analysis Toolkit: a MapReduce framework for analyzing next-generation DNA sequencing data. Genome Res. 20, 1297–1303 (2010).Bradbury, P. J. et al. TASSEL: software for association mapping of complex traits in diverse samples. Bioinformatics 23, 2633–2635 (2007).Chang, C. C. et al. Second-generation PLINK: rising to the challenge of larger and richer datasets. Gigascience 4, 7 (2015).Team, R. C. (2015). http://www.r-project.org/ .Krzywinski, M. I. et al. Circos: an information aesthetic for comparative genomics. Genome Res. 19, 1639–1645 (2009).Kosman, E. & Leonard, K. J. Similarity coefficients for molecular markers in studies of genetic relationships between individuals for haploid, diploid, and polyploid species. Mol. Ecol. 14, 415–424 (2005).Huson, D. H. & Bryant, D. Estimating Phylogenetic Trees and Networks Using SplitsTree 4. www.splitstree.org (2005).Danecek, P. et al. The variant call format and VCFtools. Bioinformatics 27, 2156–2158 (2011).Cingolani, P. et al. A program for annotating and predicting the effects of single nucleotide polymorphisms, SnpEff: SNPs in the genome of Drosophila melanogaster strainw1118; iso-2; iso-3. Fly 6, 80–92 (2012).Wu, S. et al. A common genetic mechanism underlies morphological diversity in fruits and other plant organs. Nat. Commun. 9, 4734 (2018).Drevensek, S. et al. The Arabidopsis TRM1–TON1 interaction reveals a recruitment network common to plant cortical microtubule arrays and eukaryotic centrosomes. Plant Cell 24, 178–191 (2012).Sievers, F. et al. Fast, scalable generation of high‐quality protein multiple sequence alignments using Clustal Omega. Mol. Syst. Biol. 7, 539 (2011).Nguyen, L.-T., Schmidt, H. A., von Haeseler, A. & Minh, B. Q. IQ-TREE: a fast and effective stochastic algorithm for estimating maximum-likelihood phylogenies. Mol. Biol. Evol. 32, 268–274 (2014).Kalyaanamoorthy, S., Minh, B. Q., Wong, T. K. F., von Haeseler, A. & Jermiin, L. S. ModelFinder: fast model selection for accurate phylogenetic estimates. Nat. Methods 14, 587 (2017).Hoang, D. T., Chernomor, O., von Haeseler, A., Minh, B. Q. & Vinh, L. S. UFBoot2: improving the ultrafast bootstrap approximation. Mol. Biol. Evol. 35, 518–522 (2017).Bailey, T. L. et al. MEME SUITE: tools for motif discovery and searching. Nucleic Acids Res. 37, W202–W208 (2009).Leida, C. et al. Variability of candidate genes, genetic structure and association with sugar accumulation and climacteric behavior in a broad germplasm collection of melon (Cucumis melo L.). BMC Genet. 16, 28 (2015).Esteras, C. et al. SNP genotyping in melons: genetic variation, population structure, and linkage disequilibrium. Theor. Appl. Genet. 126, 1285–1303 (2013).Maria José Gonzalo et al. Re-evaluation of the role of Indian germplasm as center of melon diversification based on genotyping-by-sequencing analysis. BMC Genom. 20, p. 448 (2019).Nimmakayala, P. et al. Single nucleotide polymorphisms generated by genotyping by sequencing to characterize genome-wide diversity, linkage disequilibrium, and selective sweeps in cultivated watermelon. BMC Genom. 15, 767 (2014).Gonzalo, M. J. & Monforte, A. J. in Genetics and Genomics of Cucurbitaceae, Grumet, Rebecca, Katzir, Nurit, Garcia-Mas, Jordi (Eds.) 269–290 (Springer, New York, U.S.A., 2016).Pomares-Viciana, T. et al. First RNA-seq approach to study fruit set and parthenocarpy in zucchini (Cucurbita pepo L.). BMC Plant Biol. 19, 61 (2019).Lu, S. et al. The cauliflower Or gene encodes a DnaJ cysteine-rich domain-containing protein that mediates high levels of β-carotene accumulation. Plant Cell 18, 3594–3605 (2006).Jin, B., Kim, J., Jung, J., Kim, D. & Park, Y. Characterization of IQ domain gene homologs as common candidate genes for elongated fruit shape in cucurbits. Hortic. Sci. Technol. 36, 85–97 (2018).van der Knaap, E. et al. What lies beyond the eye: the molecular mechanisms regulating tomato fruit weight and shape. Front. Plant Sci. 5, 227 (2014).Xiao, H., Jiang, N., Schaffner, E., Stockinger, E. J. & Van Der Knaap, E. A retrotransposon-mediated gene duplication underlies morphological variation of tomato fruit. Science 319, 1527–1530 (2008).Dou, J. et al. Genetic mapping reveals a candidate gene (ClFS1) for fruit shape in watermelon (Citrullus lanatus L.). Theor. Appl. Genet. 131, 947–958 (2018).Pan, Y. et al. Round fruit shape in WI7239 cucumber is controlled by two interacting quantitative trait loci with one putatively encoding a tomato SUN homolog. Theor. Appl. Genet. 130, 573–586 (2017).Liu, J. et al. Banana Ovate family protein MaOFP1 and MADS-box protein MuMADS1 antagonistically regulated banana fruit ripening. PLoS ONE 10, e0123870 (2015).Liu, J. et al. Mu MADS 1 and Ma OFP 1 regulate fruit quality in a tomato ovate mutant. Plant Biotechnol. J. 16, 989–1001 (2018).Cong, B., Barrero, L. S. & Tanksley, S. D. Regulatory change in YABBY-like transcription factor led to evolution of extreme fruit size during tomato domestication. Nat. Genet. 40, 800 (2008).Huang, Z., Van Houten, J., Gonzalez, G., Xiao, H. & van der Knaap, E. Genome-wide identification, phylogeny and expression analysis of SUN, OFP and YABBY gene family in tomato. Mol. Genet. Genom. 288, 111–129 (2013).Bowman, J. L. The YABBY gene family and abaxial cell fate. Curr. Opin. Plant Biol. 3, 17–22 (2000).Liu, J., Van Eck, J., Cong, B. & Tanksley, S. D. A new class of regulatory genes underlying the cause of pear-shaped tomato fruit. Proc. Natl Acad. Sci. USA 99, 13302–13306 (2002).Tsaballa, A., Pasentsis, K., Darzentas, N. & Tsaftaris, A. S. Multiple evidence for the role of an Ovate-like gene in determining fruit shape in pepper. BMC Plant Biol. 11, 46 (2011).Wang, S., Chang, Y., Guo, J. & Chen, J. G. Arabidopsis Ovate family protein 1 is a transcriptional repressor that suppresses cell elongation. Plant J. 50, 858–872 (2007).Lazzaro, M. D., Wu, S., Snouffer, A., Wang, Y. & Van Der Knaap, E. Plant organ shapes are regulated by protein interactions and associations with microtubules. Front. Plant Sci. 9, 1766 (2018)

Current challenges in postharvest biology of fruit ripening

This paper reviews the recent advances in the understanding of the fruit ripening process and describes future challenges. Fruit ripening is a complex developmental process which is orchestrated by the expression of ripening-related genes under the control of a network of signaling pathways. In climacteric fruit components responsible for the production of climacteric ethylene have been identified. Less progress has been made on non-climacteric fruit. Great advances have been made in the characterization of transcription factors (ERFs, RIN, etc...) that induce gene expression through the binding to their promoters. Genetic resources, genome sequencing and “omics” tools have been developed bringing a huge amount of data that will help to draw together an integrative network of regulatory and signaling pathways responsible for triggering and coordinating the ripening process. The discovery that some ripening events are controlled at the epigenetic level and, not in relation with the DNA sequences, opens novel perspectives

Genome-wide analysis of Dongxiang wild rice (Oryza rufipogon Griff.) to investigate lost/acquired genes during rice domestication

This file reports the functional annotation of 99,092 DXWR transcripts from the NCBI NR database using the software blast2go. This file is in the tab delimited format and can be opened using the software Excel. (TXT 12649 kb

A comprehensive genome variation map of melon identifies multiple domestication events and loci influencing agronomic traits

Melon is an economically important fruit crop that has been cultivated for thousands of years; however, the genetic basis and history of its domestication still remain largely unknown. Here we report a comprehensive map of the genomic variation in melon derived from the resequencing of 1,175 accessions, which represent the global diversity of the species. Our results suggest that three independent domestication events occurred in melon, two in India and one in Africa. We detected two independent sets of domestication sweeps, resulting in diverse characteristics of the two subspecies melo and agrestis during melon breeding. Genome-wide association studies for 16 agronomic traits identified 208 loci significantly associated with fruit mass, quality and morphological characters. This study sheds light on the domestication history of melon and provides a valuable resource for genomics-assisted breeding of this important crop.This work was supported by funding from the Agricultural Science and Technology Innovation Program (to Yongyang Xu, S.H., Z.Z. and H.W.), the China Agriculture Research System (CARS-25 to Yongyang Xu and H.W.), the Leading Talents of Guangdong Province Program (00201515 to S.H.), the Shenzhen Municipal (The Peacock Plan KQTD2016113010482651 to S.H.), the Dapeng district government, National Natural Science Foundation of China (31772304 to Z.Z.), the Science and Technology Program of Guangdong (2018B020202007 to S.H.), the National Natural Science Foundation of China (31530066 to S.H.), the National Key R&D Program of China (2016YFD0101007 to S.H.), USDA National Institute of Food and Agriculture Specialty Crop Research Initiative (2015-51181-24285 to Z.F.), the European Research Council (ERC-SEXYPARTH to A.B.), the Spanish Ministry of Economy and Competitiveness (AGL2015–64625-C2-1-R to J.G.-M.), Severo Ochoa Programme for Centres of Excellence in R&D 2016–2010 (SEV-2015–0533 to J.G.-M.), the CERCA Programme/Generalitat de Catalunya to J.G.-M. and the German Science Foundation (SPP1991 Taxon-OMICS to H.S.)

A comprehensive genome variation map of melon identifies multiple domestication events and loci influencing agronomic traits

Melon is an economically important fruit crop that has been cultivated for thousands of years; however, the genetic basis and history of its domestication still remain largely unknown. Here we report a comprehensive map of the genomic variation in melon derived from the resequencing of 1,175 accessions, which represent the global diversity of the species. Our results suggest that three independent domestication events occurred in melon, two in India and one in Africa. We detected two independent sets of domestication sweeps, resulting in diverse characteristics of the two subspecies melo and agrestis during melon breeding. Genome-wide association studies for 16 agronomic traits identified 208 loci significantly associated with fruit mass, quality and morphological characters. This study sheds light on the domestication history of melon and provides a valuable resource for genomics-assisted breeding of this important crop.info:eu-repo/semantics/acceptedVersio

Genome encode analyses reveal the basis of convergent evolution of fleshy fruit ripening

Altres ajuts: Generalitat de Catalunya/CERCA ProgrammeFleshy fruits using ethylene to regulate ripening have developed multiple times in the history of angiosperms, presenting a clear case of convergent evolution whose molecular basis remains largely unknown. Analysis of the fruitENCODE data consisting of 361 transcriptome, 71 accessible chromatin, 147 histone and 45 DNA methylation profiles reveals three types of transcriptional feedback circuits controlling ethylene-dependent fruit ripening. These circuits are evolved from senescence or floral organ identity pathways in the ancestral angiosperms either by neofunctionalisation or repurposing pre-existing genes. The epigenome, H3K27me3 in particular, has played a conserved role in restricting ripening genes and their orthologues in dry and ethylene-independent fleshy fruits. Our findings suggest that evolution of ripening is constrained by limited hormone molecules and genetic and epigenetic materials, and whole-genome duplications have provided opportunities for plants to successfully circumvent these limitations