Selection of Catechin Biosynthesis-Related Genes and Functional Analysis from Chromosome-Level Genome Assembly in C. sinensis L. Variety 'Sangmok'.

Camellia is an important plant genus that includes well-known species such as C. sinensis, C. oleifera, and C. japonica. The C. sinensis cultivar 'Sangmok', one of Korea's standard types of tea landraces, is a small evergreen tree or shrub. Genome annotation has shown that Korean tea plants have special and unique benefits and superior components, such as catechin. The genome of Camellia sinensis cultivar 'Sangmok' was assembled on the chromosome level, with a length of 2678.62 Mbp and GC content of 38.16%. Further, 15 chromosome-scale scaffolds comprising 82.43% of the assembly (BUSCO completeness, 94.3%) were identified. Analysis of 68,151 protein-coding genes showed an average of 5.003 exons per gene. Among 82,481 coding sequences, the majority (99.06%) were annotated by Uniprot/Swiss-Prot. Further analysis revealed that 'Sangmok' is closely related to C. sinensis, with a divergence time of 60 million years ago. A total of 3336 exclusive gene families in 'Sangmok' were revealed by gene ontology analysis to play roles in auxin transport and cellular response mechanisms. By comparing these exclusive genes with 551 similar catechin genes, 17 'Sangmok'-specific catechin genes were identified by qRT-PCR, including those involved in phytoalexin biosynthesis and related to cytochrome P450. The 'Sangmok' genome exhibited distinctive genes compared to those of related species. This comprehensive genomic investigation enhances our understanding of the genetic architecture of 'Sangmok' and its specialized functions. The findings contribute valuable insights into the evolutionary and functional aspects of this plant species.

NGS_SNPAnalyzer: a desktop software supporting genome projects by identifying and visualizing sequence variations from next-generation sequencing data.

BACKGROUND: Sequence variations such as single nucleotide polymorphisms are markers for genetic diseases and breeding. Therefore, identifying sequence variations is one of the main objectives of several genome projects. Although most genome project consortiums provide standard operation procedures for sequence variation detection methods, there may be differences in the results because of human selection or error. OBJECTIVE: To standardize the procedure for sequence variation detection and help researchers who are not formally trained in bioinformatics, we developed the NGS_SNPAnalyzer, a desktop software and fully automated graphical pipeline. METHODS: The NGS_SNPAnalyzer is implemented using JavaFX (version 1.8); therefore, it is not limited to any operating system (OS). The tools employed in the NGS_SNPAnalyzer were compiled on Microsoft Windows (version 7, 10) and Ubuntu Linux (version 16.04, 17.0.4). RESULTS: The NGS_SNPAnalyzer not only includes the functionalities for variant calling and annotation but also provides quality control, mapping, and filtering details to support all procedures from next-generation sequencing (NGS) data to variant visualization. It can be executed using pre-set pipelines and options and customized via user-specified options. Additionally, the NGS_SNPAnalyzer provides a user-friendly graphical interface and can be installed on any OS that supports JAVA. CONCLUSIONS: Although there are several pipelines and visualization tools available for NGS data analysis, we developed the NGS_SNPAnalyzer to provide the user with an easy-to-use interface. The benchmark test results indicate that the NGS_SNPAnayzer achieves better performance than other open source tools.

The Complete Chloroplast Genome of the Hare's Ear Root, Bupleurum falcatum: Its Molecular Features.

Bupleurum falcatum, which belongs to the family Apiaceae, has long been applied for curative treatments, especially as a liver tonic, in herbal medicine. The chloroplast (cp) genome has been an ideal model to perform the evolutionary and comparative studies because of its highly conserved features and simple structure. The Apiaceae family is taxonomically close to the Araliaceae family and there have been numerous complete chloroplast genome sequences reported in the Araliaceae family, while little is known about the Apiaceae family. In this study, the complete sequence of the B. falcatum chloroplast genome was obtained. The full-length of the cp genome is 155,989 nucleotides with a 37.66% overall guanine-cytosine (GC) content and shows a quadripartite structure composed of three nomenclatural regions: a large single-copy (LSC) region, a small single-copy (SSC) region, and a pair of inverted repeat (IR) regions. The genome occupancy is 85,912-bp, 17,517-bp, and 26,280-bp for LSC, SSC, and IR, respectively. B. falcatum was shown to contain 111 unique genes (78 for protein-coding, 29 for tRNAs, and four for rRNAs, respectively) on its chloroplast genome. Genic comparison found that B. falcatum has no pseudogenes and has two gene losses, accD in the LSC and ycf15 in the IRs. A total of 55 unique tandem repeat sequences were detected in the B. falcatum cp genome. This report is the first to describe the complete chloroplast genome sequence in B. falcatum and will open up further avenues of research to understand the evolutionary panorama and the chloroplast genome conformation in related plant species.

Functional classification of rice flanking sequence tagged genes using MapMan terms and global understanding on metabolic and regulatory pathways affected by dxr mutant having defects in light response.

BACKGROUND: Rice is one of the most important food crops for humans. To improve the agronomical traits of rice, the functions of more than 1,000 rice genes have been recently characterized and summarized. The completed, map-based sequence of the rice genome has significantly accelerated the functional characterization of rice genes, but progress remains limited in assigning functions to all predicted non-transposable element (non-TE) genes, estimated to number 37,000-41,000. RESULTS: The International Rice Functional Genomics Consortium (IRFGC) has generated a huge number of gene-indexed mutants by using mutagens such as T-DNA, Tos17 and Ds/dSpm. These mutants have been identified by 246,566 flanking sequence tags (FSTs) and cover 65 % (25,275 of 38,869) of the non-TE genes in rice, while the mutation ratio of TE genes is 25.7 %. In addition, almost 80 % of highly expressed non-TE genes have insertion mutations, indicating that highly expressed genes in rice chromosomes are more likely to have mutations by mutagens such as T-DNA, Ds, dSpm and Tos17. The functions of around 2.5 % of rice genes have been characterized, and studies have mainly focused on transcriptional and post-transcriptional regulation. Slow progress in characterizing the function of rice genes is mainly due to a lack of clues to guide functional studies or functional redundancy. These limitations can be partially solved by a well-categorized functional classification of FST genes. To create this classification, we used the diverse overviews installed in the MapMan toolkit. Gene Ontology (GO) assignment to FST genes supplemented the limitation of MapMan overviews. CONCLUSION: The functions of 863 of 1,022 known genes can be evaluated by current FST lines, indicating that FST genes are useful resources for functional genomic studies. We assigned 16,169 out of 29,624 FST genes to 34 MapMan classes, including major three categories such as DNA, RNA and protein. To demonstrate the MapMan application on FST genes, transcriptome analysis was done from a rice mutant of 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) gene with FST. Mapping of 756 down-regulated genes in dxr mutants and their annotation in terms of various MapMan overviews revealed candidate genes downstream of DXR-mediating light signaling pathway in diverse functional classes such as the methyl-D-erythritol 4-phosphatepathway (MEP) pathway overview, photosynthesis, secondary metabolism and regulatory overview. This report provides a useful guide for systematic phenomics and further applications to enhance the key agronomic traits of rice.

Elucidating the triplicated ancestral genome structure of radish based on chromosome-level comparison with the Brassica genomes.

KEYMESSAGE: This study presents a chromosome-scale draft genome sequence of radish that is assembled into nine chromosomal pseudomolecules. A comprehensive comparative genome analysis with the Brassica genomes provides genomic evidences on the evolution of the mesohexaploid radish genome. Radish (Raphanus sativus L.) is an agronomically important root vegetable crop and its origin and phylogenetic position in the tribe Brassiceae is controversial. Here we present a comprehensive analysis of the radish genome based on the chromosome sequences of R. sativus cv. WK10039. The radish genome was sequenced and assembled into 426.2 Mb spanning >98 % of the gene space, of which 344.0 Mb were integrated into nine chromosome pseudomolecules. Approximately 36 % of the genome was repetitive sequences and 46,514 protein-coding genes were predicted and annotated. Comparative mapping of the tPCK-like ancestral genome revealed that the radish genome has intermediate characteristics between the Brassica A/C and B genomes in the triplicated segments, suggesting an internal origin from the genus Brassica. The evolutionary characteristics shared between radish and other Brassica species provided genomic evidences that the current form of nine chromosomes in radish was rearranged from the chromosomes of hexaploid progenitor. Overall, this study provides a chromosome-scale draft genome sequence of radish as well as novel insight into evolution of the mesohexaploid genomes in the tribe Brassiceae.

Construction of a reference genetic map of Raphanus sativus based on genotyping by whole-genome resequencing.

KEY MESSAGE: This manuscript provides a genetic map of Raphanus sativus that has been used as a reference genetic map for an ongoing genome sequencing project. The map was constructed based on genotyping by whole-genome resequencing of mapping parents and F 2 population. Raphanus sativus is an annual vegetable crop species of the Brassicaceae family and is one of the key plants in the seed industry, especially in East Asia. Assessment of the R. sativus genome provides fundamental resources for crop improvement as well as the study of crop genome structure and evolution. With the goal of anchoring genome sequence assemblies of R. sativus cv. WK10039 whose genome has been sequenced onto the chromosomes, we developed a reference genetic map based on genotyping of two parents (maternal WK10039 and paternal WK10024) and 93 individuals of the F2 mapping population by whole-genome resequencing. To develop high-confidence genetic markers, ~83 Gb of parental lines and ~591 Gb of mapping population data were generated as Illumina 100 bp paired-end reads. High stringent sequence analysis of the reads mapped to the 344 Mb of genome sequence scaffolds identified a total of 16,282 SNPs and 150 PCR-based markers. Using a subset of the markers, a high-density genetic map was constructed from the analysis of 2,637 markers spanning 1,538 cM with 1,000 unique framework loci. The genetic markers integrated 295 Mb of genome sequences to the cytogenetically defined chromosome arms. Comparative analysis of the chromosome-anchored sequences with Arabidopsis thaliana and Brassica rapa revealed that the R. sativus genome has evident triplicated sub-genome blocks and the structure of gene space is highly similar to that of B. rapa. The genetic map developed in this study will serve as fundamental genomic resources for the study of R. sativus.

Inactivation of the CTD phosphatase-like gene OsCPL1 enhances the development of the abscission layer and seed shattering in rice.

Although susceptibility to seed shattering causes severe yield loss during cereal crop harvest, it is an adaptive trait for seed dispersal in wild plants. We previously identified a recessive shattering locus, sh-h, from the rice shattering mutant line Hsh that carries an enhanced abscission layer. Here, we further mapped sh-h to a 34-kb region on chromosome 7 by analyzing 240 F(2) plants and five F(3) lines from the cross between Hsh and Blue&Gundil. Hsh had a point mutation at the 3' splice site of the seventh intron within LOC_Os07g10690, causing a 15-bp deletion of its mRNA as a result of altered splicing. Two transferred DNA (T-DNA) insertion mutants and one point mutant exhibited the enhanced shattering phenotype, confirming that LOC_Os07g10690 is indeed the sh-h gene. RNA interference (RNAi) transgenic lines with suppressed expression of this gene exhibited greater shattering. This gene, which encodes a protein containing a conserved carboxy-terminal domain (CTD) phosphatase domain, was named Oryza sativa CTD phosphatase-like 1 (OsCPL1). Subcellular localization and biochemical analysis revealed that the OsCPL1 protein is a nuclear phosphatase, a common characteristic of metazoan CTD phosphatases involved in cell differentiation. These results demonstrate that OsCPL1 represses differentiation of the abscission layer during panicle development.

A Ds-insertion mutant of OSH6 (Oryza sativa Homeobox 6) exhibits outgrowth of vestigial leaf-like structures, bracts, in rice.

OSH6 (Oryza sativa Homeobox6) is an ortholog of lg3 (Liguleless3) in maize. We generated a novel allele, termed OSH6-Ds, by inserting a defective Ds element into the third exon of OSH6, which resulted in a truncated OSH6 mRNA. The truncated mRNA was expressed ectopically in leaf tissues and encoded the N-terminal region of OSH6, which includes the KNOX1 and partial KNOX2 subdomains. This recessive mutant showed outgrowth of bracts or produced leaves at the basal node of the panicle. These phenotypes distinguished it from the OSH6 transgene whose ectopic expression led to a "blade to sheath transformation" phenotype at the midrib region of leaves, similar to that seen in dominant Lg3 mutants. Expression of a similar truncated OSH6 cDNA from the 35S promoter (35S::DeltaOSH6) confirmed that the ectopic expression of this product was responsible for the aberrant bract development. These data suggest that OSH6-Ds interferes with a developmental mechanism involved in bract differentiation, especially at the basal nodes of panicles.

Analysis of gene-trap Ds rice populations in Korea.

Insertional mutagen-mediated gene tagging populations have been essential resources for analyzing the function of plant genes. In rice, maize transposable elements have been successfully utilized to produce transposant populations. However, many generations and substantial field space are required to obtain a sufficiently sized transposant population. In rice, the japonica and indica subspecies are phenotypically and genetically divergent. Here, callus cultures with seeds carrying Ac and Ds were used to produce 89,700 lines of Dongjin, a japonica cultivar, and 6,200 lines of MGRI079, whose genome is composed of a mixture of the genetic backgrounds of japonica and indica. Of the more than 3,000 lines examined, 67% had Ds elements. Among the Ds-carrying lines, 81% of Dongjin and 63% of MGRI079 contained transposed Ds, with an average of around 2.0 copies. By examining more than 15,000 lines, it was found that 12% expressed the reporter gene GUS during the early-seedling stage. GUS was expressed in root hairs and crown root initials at estimated frequencies of 0.78% and 0.34%, respectively. The 5,271 analyzed Ds loci were found to be randomly distributed over all of the rice chromosomes.

PLASTOCHRON1, a timekeeper of leaf initiation in rice, encodes cytochrome P450.

During postembryonic development of higher plants, the shoot apical meristem produces lateral organs in a regular spacing (phyllotaxy) and a regular timing (plastochron). Molecular analysis of mutants associated with phyllotaxy and plastochron would greatly increase understanding of the developmental mechanism of plant architecture because phyllotaxy and plastochron are fundamental regulators of plant architecture. pla1 of rice is not only a plastochron mutant showing rapid leaf initiation without affecting phyllotaxy, but also a heterochronic mutant showing ectopic shoot formation in the reproductive phase. Thus, pla1 provides a tool for analyzing the molecular basis of temporal regulation in leaf development. In this work, we isolated the PLA1 gene by map-based cloning. The identified PLA1 gene encodes a cytochrome P450, CYP78A11, which potentially catalyzes substances controlling plant development. PLA1 is expressed in developing leaf primordia, bracts of the panicle, and elongating internodes, but not in the shoot apical meristem. The expression pattern and mutant phenotype suggest that the PLA1 gene acting in developing leaf primordia affects the timing of successive leaf initiation and the termination of vegetative growth.