De novo transcriptome assembly and novel microsatellite marker information in Capsicum annuum varieties Saengryeg 211 and Saengryeg 213

Sequencing and de novo transcriptome assembly for discovering regulators of gene expression in Jack (Artocarpus heterophyllus)

Jack (Artocarpus heterophyllus) is a multipurpose fruit-tree species with minimal genomic resources. The study reports developing comprehensive transcriptome data containing 80,411 unigenes with an N50 value of 1265 bp. We predicted 64,215 CDSs from the unigenes and annotated and functionally categorized them into the biological process (23,230), molecular function (27,149), and cellular components (17,284). From 80,411 unigenes, we discovered 16,853 perfect SSRs with 192 distinct repeat motif types reiterating 4 to 22 times. Besides, we identified 2741 TFs from 69 TF families, 53 miRNAs from 19 conserved miRNA families, 25,953 potential lncRNAs, and placed three functional eTMs in different lncRNA-miRNA pairs. The regulatory networks involving genes, TFs, and miRNAs identified several regulatory and regulated nodes providing insight into miRNAs' gene associations and transcription factor-mediated regulation. The comparison of expression patterns of some selected miRNAs vis-à-vis their corresponding target genes showed an inverse relationship indicating the possible miRNA-mediated regulation of the genes.

Next-Generation Sequencing Approaches in Genome-Wide Discovery of Single Nucleotide Polymorphism Markers Associated with Pungency and Disease Resistance in Pepper

Pepper is an economically important horticultural plant that has been widely used for its pungency and spicy taste in worldwide cuisines. Therefore, the domestication of pepper has been carried out since antiquity. Owing to meet the growing demand for pepper with high quality, organoleptic property, nutraceutical contents, and disease tolerance, genomics assisted breeding techniques can be incorporated to develop novel pepper varieties with desired traits. The application of next-generation sequencing (NGS) approaches has reformed the plant breeding technology especially in the area of molecular marker assisted breeding. The availability of genomic information aids in the deeper understanding of several molecular mechanisms behind the vital physiological processes. In addition, the NGS methods facilitate the genome-wide discovery of DNA based markers linked to key genes involved in important biological phenomenon. Among the molecular markers, single nucleotide polymorphism (SNP) indulges various benefits in comparison with other existing DNA based markers. The present review concentrates on the impact of NGS approaches in the discovery of useful SNP markers associated with pungency and disease resistance in pepper. The information provided in the current endeavor can be utilized for the betterment of pepper breeding in future.

RNA-Seq of Guar (Cyamopsis tetragonoloba, L. Taub.) Leaves: De novo Transcriptome Assembly, Functional Annotation and Development of Genomic Resources

Genetic improvement in industrially important guar (Cyamopsis tetragonoloba, L. Taub.) crop has been hindered due to the lack of sufficient genomic or transcriptomic resources. In this study, RNA-Seq technology was employed to characterize the transcriptome of leaf tissues from two guar varieties, namely, M-83 and RGC-1066. Approximately 30 million high-quality pair-end reads of each variety generated by Illumina HiSeq platform were used for de novo assembly by Trinity program. A total of 62,146 non-redundant unigenes with an average length of 679 bp were obtained. The quality assessment of assembled unigenes revealed 87.50% of complete and 97.18% partial core eukaryotic genes (CEGs). Sequence similarity analyses and annotation of the unigenes against non-redundant protein (Nr) and Gene Ontology (GO) databases identified 175,882 GO annotations. A total of 11,308 guar unigenes were annotated with various enzyme codes (EC) and categorized in six categories with 55 subclasses. The annotation of biochemical pathways resulted in a total of 11,971 unigenes assigned with 145 KEGG maps and 1759 enzyme codes. The species distribution analysis of the unigenes showed highest similarity with Glycine max genes. A total of 5773 potential simple sequence repeats (SSRs) and 3594 high-quality single nucleotide polymorphisms (SNPs) were identified. Out of 20 randomly selected SSRs for wet laboratory validation, 13 showed consistent PCR amplification in both guar varieties. In silico studies identified 145 polymorphic SSR markers in two varieties. To the best of our knowledge, this is the first report on transcriptome analysis and SNPs identification in guar till date.

A comprehensive characterization of simple sequence repeats in pepper genomes provides valuable resources for marker development in Capsicum

The sequences of the full set of pepper genomes including nuclear, mitochondrial and chloroplast are now available for use. However, the overall of simple sequence repeats (SSR) distribution in these genomes and their practical implications for molecular marker development in Capsicum have not yet been described. Here, an average of 868,047.50, 45.50 and 30.00 SSR loci were identified in the nuclear, mitochondrial and chloroplast genomes of pepper, respectively. Subsequently, systematic comparisons of various species, genome types, motif lengths, repeat numbers and classified types were executed and discussed. In addition, a local database composed of 113,500 in silico unique SSR primer pairs was built using a homemade bioinformatics workflow. As a pilot study, 65 polymorphic markers were validated among a wide collection of 21 Capsicum genotypes with allele number and polymorphic information content value per marker raging from 2 to 6 and 0.05 to 0.64, respectively. Finally, a comparison of the clustering results with those of a previous study indicated the usability of the newly developed SSR markers. In summary, this first report on the comprehensive characterization of SSR motifs in pepper genomes and the very large set of SSR primer pairs will benefit various genetic studies in Capsicum.

Construction of an interspecific genetic map based on InDel and SSR for mapping the QTLs affecting the initiation of flower primordia in pepper (Capsicum spp.)

Re-sequencing permits the mining of genome-wide variations on a large scale and provides excellent resources for the research community. To accelerate the development and application of molecular markers and identify the QTLs affecting the flowering time-related trait in pepper, a total of 1,038 pairs of InDel and 674 SSR primers from different sources were used for genetic mapping using the F2 population (n = 154) derived from a cross between BA3 (C. annuum) and YNXML (C. frutescens). Of these, a total of 224 simple PCR-based markers, including 129 InDels and 95 SSRs, were validated and integrated into a map, which was designated as the BY map. The BY map consisted of 13 linkage groups (LGs) and spanned a total genetic distance of 1,249.77 cM with an average marker distance of 5.60 cM. Comparative analysis of the genetic and physical map based on the anchored markers showed that the BY map covered nearly the whole pepper genome. Based on the BY map, one major and five minor QTLs affecting the number of leaves on the primary axis (Nle) were detected on chromosomes P2, P7, P10 and P11 in 2012. The major QTL on P2 was confirmed based on another subset of the same F2 population (n = 147) in 2014 with selective genotyping of markers from the BY map. With the accomplishment of pepper whole genome sequencing and annotations (release 2.0), 153 candidate genes were predicted to embed in the Nle2.2 region, of which 12 important flowering related genes were obtained. The InDel/SSR-based interspecific genetic map, QTLs and candidate genes obtained by the present study will be useful for the downstream isolation of flowering time-related gene and other genetic applications for pepper.