BjuWRR1, a CNL-type R gene, was identified from an east European gene pool line of Brassica juncea and validated for conferring resistance to white rust by genetic transformation. White rust caused by the oomycete pathogen Albugo candida is a significant disease of crucifer crops including Brassica juncea (mustard), a major oilseed crop of the Indian subcontinent. Earlier, a resistance-conferring locus named AcB1-A5.1 was mapped in an east European gene pool line of B. juncea-Donskaja-IV. This line was tested along with some other lines of B. juncea (AABB), B. rapa (AA) and B. nigra (BB) for resistance to six isolates of…
Arogyapacha, the local name of Trichopus zeylanicus, is a rare, indigenous medicinal plant of India. This plant is famous for its traditional use as an instant energy stimulant. So far, no genomic resource is available for this important plant and hence its metabolic pathways are poorly understood. Here, we report on a high-quality draft assembly of approximately 713.4 Mb genome of T. zeylanicus, first draft genome from the genus Trichopus The assembly was generated in a hybrid approach using Illumina short-reads and Pacbio longer-reads. The total assembly comprised of 22601 scaffolds with an N50 value of 433.3 Kb. We predicted…
Infectious disease is both a major force of selection in nature and a prime cause of yield loss in agriculture. In plants, disease resistance is often conferred by nucleotide-binding leucine-rich repeat (NLR) proteins, intracellular immune receptors that recognize pathogen proteins and their effects on the host. Consistent with extensive balancing and positive selection, NLRs are encoded by one of the most variable gene families in plants, but the true extent of intraspecific NLR diversity has been unclear. Here, we define a nearly complete species-wide pan-NLRome in Arabidopsis thaliana based on sequence enrichment and long-read sequencing. The pan-NLRome largely saturates with…
Advances in genome sequencing and assembly technologies are generating many high-quality genome sequences, but assemblies of large, repeat-rich polyploid genomes, such as that of bread wheat, remain fragmented and incomplete. We have generated a new wheat whole-genome shotgun sequence assembly using a combination of optimized data types and an assembly algorithm designed to deal with large and complex genomes. The new assembly represents >78% of the genome with a scaffold N50 of 88.8 kb that has a high fidelity to the input data. Our new annotation combines strand-specific Illumina RNA-seq and Pacific Biosciences (PacBio) full-length cDNAs to identify 104,091 high-confidence…
Computational analyses play crucial roles in characterizing splicing isoforms in plant genomes. In this review, we provide a survey of computational tools used in recently published, genome-scale splicing analyses in plants. We summarize the commonly used software and pipelines for read mapping, isoform reconstruction, isoform quantification, and differential expression analysis. We also discuss methods for analyzing long reads and the strategies to combine long and short reads in identifying splicing isoforms. We review several tools for characterizing local splicing events, splicing graphs, coding potential, and visualizing splicing isoforms. We further discuss the procedures for identifying conserved splicing isoforms across plant…
Phased, secondary siRNAs (phasiRNAs) are found widely in plants, from protein-coding transcripts and long, non-coding RNAs; animal piRNAs are also phased. Integrated methods characterizing textquotedblleftPHAStextquotedblright loci are unavailable, and existing methods are quite limited and inefficient in handling large volumes of sequencing data. The PHASIS suite described here provides complete tools for the computational characterization of PHAS loci, with an emphasis on plants, in which these loci are numerous. Benchmarked comparisons demonstrate that PHASIS is sensitive, highly scalable and fast. Importantly, PHASIS eliminates the requirement of a sequenced genome and PARE/degradome data for discovery of phasiRNAs and their miRNA triggers.
This meeting report highlights key trends that emerged from a conference entitled Post-Transcriptional Gene Regulation in Plants, which was held 14-15 July 2016, as a satellite meeting of the annual meeting of the American Society of Plant Biologists in Austin, Texas. The molecular biology of RNA is emerging as an integral part of the framework for plants’ responses to environmental challenges such as drought and heat, hypoxia, nutrient deprivation, light and pathogens. Moreover, the conference illustrated how a multitude of customized and pioneering omics-related technologies are being applied, more and more often in combination, to describe and dissect the complexities…
Sugar pine (Pinus lambertiana Douglas) is within the subgenus Strobus with an estimated genome size of 31 Gbp. Transcriptomic resources are of particular interest in conifers due to the challenges presented in their megagenomes for gene identification. In this study, we present the first comprehensive survey of the P. lambertiana transcriptome through deep sequencing of a variety of tissue types to generate more than 2.5 billion short reads. Third generation, long reads generated through PacBio Iso-Seq has been included for the first time in conifers to combat the challenges associated with de novo transcriptome assembly. A technology comparison is provided…
In grasses, two pathways that generate diverse and numerous 21-nt (premeiotic) and 24-nt (meiotic) phased siRNAs are highly enriched in anthers, the male reproductive organs. These “phasiRNAs” are analogous to mammalian piRNAs, yet their functions and evolutionary origins remain largely unknown. The 24-nt meiotic phasiRNAs have only been described in grasses, wherein their biogenesis is dependent on a specialized Dicer (DCL5). To assess how evolution gave rise to this pathway, we examined reproductive phasiRNA pathways in nongrass monocots: garden asparagus, daylily, and lily. The common ancestors of these species diverged approximately 115-117 million years ago (MYA). We found that premeiotic…
Plant immune receptors are under constant selective pressure to maintain resistance to plant pathogens. Nucleotide-binding leucine-rich repeat (NLR) proteins are one class of cytoplasmic immune receptors whose genes commonly show signatures of adaptive evolution. While it is known that balancing selection contributes to maintaining high intraspecific allelic diversity, the evolutionary mechanism that influences the transmission of alleles during speciation remains unclear. The barley Mla locus has over 30 described alleles conferring isolate-specific resistance to barley powdery mildew and contains three NLR families (RGH1, RGH2, and RGH3). We discovered (using sequence capture and RNAseq) the presence of a novel integrated Exo70…
The divergence patterns of NBS – LRR genes in soybean Rsv3 locus were deciphered and several divergent alleles ( NBS_C, NBS_D and Columbia NBS_E ) were identified as the likely functional candidates of Rsv3. The soybean Rsv3 locus, which confers resistance to the soybean mosaic virus (SMV), has been previously mapped to a region containing five nucleotide binding site-leucine-rich repeats (NBS-LRR) genes (referred to as nbs_A-E) in Williams 82. In resistant cultivars, however, the number of NBS-LRR genes in this region and their divergence from susceptible alleles remain unclear. In the present study, we constructed and screened a bacterial artificial…
Nucleotide-binding (NB-ARC), leucine-rich-repeat genes (NLRs) account for 60.8% of resistance (R) genes molecularly characterized from plants. NLRs exist as large gene families prone to tandem duplication and transposition, with high sequence diversity among crops and their wild relatives. This diversity can be a source of new disease resistance, but difficulty in distinguishing specific sequences from homologous gene family members hinders characterization of resistance for improving crop varieties. Current genome sequencing and assembly technologies, especially those using long-read sequencing, are improving resolution of repeat-rich genomic regions and clarifying locations of duplicated genes, such as NLRs. Using the conserved NB-ARC domain as…
Understanding how crop plants evolved from their wild relatives and spread around the world can inform about the origins of agriculture. Here, we review how the rapid development of genomic resources and tools has made it possible to conduct genetic mapping and population genetic studies to unravel the molecular underpinnings of domestication and crop evolution in diverse crop species. We propose three future avenues for the study of crop evolution: establishment of high-quality reference genomes for crops and their wild relatives; genomic characterization of germplasm collections; and the adoption of novel methodologies such as archaeogenetics, epigenomics, and genome editing.
Following the often short-lived protection that major nucleotide binding, leucine-rich-repeat (NB-LRR) resistance genes offer against the potato pathogen Phytophthora infestans, field resistance was thought to provide a more durable alternative to prevent late blight disease. We previously identified the QTL dPI09c on potato chromosome 9 as a more durable field resistance source against late blight. Here, the resistance QTL was fine-mapped to a 186 kb region. The interval corresponds to a larger, 389 kb, genomic region in the potato reference genome of Solanum tuberosum Group Phureja doubled monoploid clone DM1-3 (DM) and from which functional NB-LRRs R8, R9a, Rpi-moc1, and…