Tomato (Solanum lycopersicum) is a major crop plant and a model system for fruit development. Solanum is one of the largest angiosperm genera(1) and includes annual and perennial plants from diverse habitats. Here we present a high-quality genome sequence of domesticated tomato, a draft sequence of its closest wild relative, Solanum pimpinellifolium(2), and compare them to each other and to the potato genome (Solanum tuberosum). The two tomato genomes show only 0.6% nucleotide divergence and signs of recent admixture, but show more than 8% divergence from potato, with nine large and several smaller inversions. In contrast to Arabidopsis, but similar to soybean, tomato and potato small RNAs map predominantly to gene-rich chromosomal regions, including gene promoters. The Solanum lineage has experienced two consecutive genome triplications: one that is ancient and shared with rosids, and a more recent one. These triplications set the stage for the neofunctionalization of genes controlling fruit characteristics, such as colour and fleshiness

No abstract

BackgroundTransposable elements are major evolutionary forces which can cause new genome structure and species diversification. The role of transposable elements in the expansion of nucleotide-binding and leucine-rich-repeat proteins (NLRs), the major disease-resistance gene families, has been unexplored in plants.ResultsWe report two high-quality de novo genomes (Capsicum baccatum and C. chinense) and an improved reference genome (C. annuum) for peppers. Dynamic genome rearrangements involving translocations among chromosomes 3, 5, and 9 were detected in comparison between C. baccatum and the two other peppers. The amplification of athila LTR-retrotransposons, members of the gypsy superfamily, led to genome expansion in C. baccatum. In-depth genome-wide comparison of genes and repeats unveiled that the copy numbers of NLRs were greatly increased by LTR-retrotransposon-mediated retroduplication. Moreover, retroduplicated NLRs are abundant across the angiosperms and, in most cases, are lineage-specific.ConclusionsOur study reveals that retroduplication has played key roles for the massive emergence of NLR genes including functional disease-resistance genes in pepper plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-017-1341-9) contains supplementary material, which is available to authorized users.

Highlights d The Striga genome reflects a three-phase model of parasitic plant genome evolution d A family of strigolactone receptors has undergone a striking expansion in Striga d Genes in lateral root development are coordinately induced in a parasitic organ d Host genes and retrotransposons are horizontally transferred into Striga

Most agricultural traits are controlled by quantitative trait loci (QTLs); however, there are few studies on QTL mapping of horticultural traits in pepper (Capsicum spp.) due to the lack of high-density molecular maps and the sequence information. In this study, an ultra-high-density map and 120 recombinant inbred lines (RILs) derived from a cross between C. annuum ‘Perennial’ and C. annuum ‘Dempsey’ were used for QTL mapping of horticultural traits. Parental lines and RILs were resequenced at 18× and 1× coverage, respectively. Using a sliding window approach, an ultra-high-density bin map containing 2,578 bins was constructed. The total map length of the map was 1,372 cM, and the average interval between bins was 0.53 cM. A total of 86 significant QTLs controlling 17 horticultural traits were detected. Among these, 32 QTLs controlling 13 traits were major QTLs. Our research shows that the construction of bin maps using low-coverage sequence is a powerful method for QTL mapping, and that the short intervals between bins are helpful for fine-mapping of QTLs. Furthermore, bin maps can be used to improve the quality of reference genomes by elucidating the genetic order of unordered regions and anchoring unassigned scaffolds to linkage groups.

Plants have evolved an elaborate innate immune system against invading pathogens. Within this system, intracellular nucleotide-binding leucine-rich repeat (NLR) immune receptors are known play critical roles in effector-triggered immunity (ETI) plant defense. We performed genome-wide identification and classification of NLR-coding sequences from the genomes of pepper, tomato, and potato using fixed criteria. We then compared genomic duplication and evolution features. We identified intact 267, 443, and 755 NLR-encoding genes in tomato, potato, and pepper genomes, respectively. Phylogenetic analysis and classification of Solanaceae NLRs revealed that the majority of NLR super family members fell into 14 subgroups, including a TIR-NLR (TNL) subgroup and 13 non-TNL subgroups. Specific subgroups have expanded in each genome, with the expansion in pepper showing subgroup-specific physical clusters. Comparative analysis of duplications showed distinct duplication patterns within pepper and among Solanaceae plants suggesting subgroup- or species-specific gene duplication events after speciation, resulting in divergent evolution. Taken together, genome-wide analysis of NLR family members provide insights into their evolutionary history in Solanaceae. These findings also provide important foundational knowledge for understanding NLR evolution and will empower broader characterization of disease resistance genes to be used for crop breeding.

Summary Panax ginseng C. A. Meyer, reputed as the king of medicinal herbs, has slow growth, long generation time, low seed production and complicated genome structure that hamper its study. Here, we unveil the genomic architecture of tetraploid P. ginseng by de novo genome assembly, representing 2.98 Gbp with 59 352 annotated genes. Resequencing data indicated that diploid Panax species diverged in association with global warming in Southern Asia, and two North American species evolved via two intercontinental migrations. Two whole genome duplications (WGD) occurred in the family Araliaceae (including Panax) after divergence with the Apiaceae, the more recent one contributing to the ability of P. ginseng to overwinter, enabling it to spread broadly through the Northern Hemisphere. Functional and evolutionary analyses suggest that production of pharmacologically important dammarane‐type ginsenosides originated in Panax and are produced largely in shoot tissues and transported to roots; that newly evolved P. ginseng fatty acid desaturases increase freezing tolerance; and that unprecedented retention of chlorophyll a/b binding protein genes enables efficient photosynthesis under low light. A genome‐scale metabolic network provides a holistic view of Panax ginsenoside biosynthesis. This study provides valuable resources for improving medicinal values of ginseng either through genomics‐assisted breeding or metabolic engineering.

Transcription activator-like effector (TALE) proteins of the plant pathogenic bacterial genus Xanthomonas bind to and transcriptionally activate host susceptibility genes, promoting disease. Plant immune systems have taken advantage of this mechanism by evolving TALE binding sites upstream of resistance ( R ) genes. For example, the pepper Bs3 and rice Xa27 genes are hypersensitive reaction plant R genes that are transcriptionally activated by corresponding TALEs. Both R genes have a hallmark expression pattern in which their transcripts are detectable only in the presence and not the absence of the corresponding TALE. By transcriptome profiling using next-generation sequencing (RNA-seq), we tested whether we could avoid laborious positional cloning for the isolation of TALE-induced R genes. In a proof-of-principle experiment, RNA-seq was used to identify a candidate for Bs4C , an R gene from pepper that mediates recognition of the Xanthomonas TALE protein AvrBs4. We identified one major Bs4C candidate transcript by RNA-seq that was expressed exclusively in the presence of AvrBs4. Complementation studies confirmed that the candidate corresponds to the Bs4C gene and that an AvrBs4 binding site in the Bs4C promoter directs its transcriptional activation. Comparison of Bs4C with a nonfunctional allele that is unable to recognize AvrBs4 revealed a 2-bp polymorphism within the TALE binding site of the Bs4C promoter. Bs4C encodes a structurally unique R protein and Bs4C -like genes that are present in many solanaceous genomes seem to be as tightly regulated as pepper Bs4C . These findings demonstrate that TALE-specific R genes can be cloned from large-genome crops with a highly efficient RNA-seq approach.