Whole-genome sequencing reveals uniqueness of black-hulled and straw-hulled weedy rice genomes

Harnessing weedy rice as functional food and source of novel traits for crop improvement

A relative of cultivated rice (Oryza sativa L.), weedy or red rice (Oryza spp.) is currently recognized as the dominant weed, leading to a drastic loss of yield of cultivated rice due to its highly competitive abilities like producing more tillers, panicles, and biomass with better nutrient uptake. Due to its high nutritional value, antioxidant properties (anthocyanin and proanthocyanin), and nutrient absorption ability, weedy rice is gaining immense research attentions to understand its genetic constitution to augment future breeding strategies and to develop nutrition-rich functional foods. Consequently, this review focuses on the unique gene source of weedy rice to enhance the cultivated rice for its crucial features like water use efficiency, abiotic and biotic stress tolerance, early flowering, and the red pericarp of the seed. It explores the debating issues on the origin and evolution of weedy rice, including its high diversity, signalling aspects, quantitative trait loci (QTL) mapping under stress conditions, the intricacy of the mechanism in the expression of the gene flow, and ecological challenges of nutrient removal by weedy rice. This review may create a foundation for future researchers to understand the gene flow between cultivated crops and weedy traits and support an improved approach for the applicability of several models in predicting multiomics variables.

A gene expression atlas of Nicotiana tabacum across various tissues at transcript resolution

Alternative splicing (AS) expands the transcriptome diversity by selectively splicing exons and introns from pre-mRNAs to generate different protein isoforms. This mechanism is widespread in eukaryotes and plays a crucial role in development, environmental adaptation, and stress resistance. In this study, we collected 599 tobacco RNA-seq datasets from 35 projects. 207,689 transcripts were identified in this study, of which 35,519 were annotated in the reference genome, while 172,170 transcripts were newly annotated. Additionally, tissue-specific analysis revealed 4,585 transcripts that were uniquely expressed in different tissues, highlighting the complexity and specialization of tobacco gene expression. The analysis of AS events (ASEs) across different tissues showed significant variability in the expression levels of ASE-derived transcripts, with some of these transcripts being associated with stress resistance, such as the geranyl diphosphate synthase (GGPPS). Moreover, we identified 21,763 splicing quantitative trait locus (sQTLs), which were enriched in genes involved in biological processes such as histone acetylation. Furthermore, sQTLs involved genes related to plant hormone signal transduction, terpenoid backbone biosynthesis, and other resistance pathways. These findings not only reveal the diversity of gene expression in tobacco but also provide new insights and strategies for improving tobacco quality and resistance.

Pan-genomics: Insight into the Functional Genome, Applications, Advancements, and Challenges

A pan-genome is a compilation of the common and unique genomes found in a given species. It incorporates the genetic information from all of the genomes sampled, producing a big and diverse set of genetic material. Pan-genomic analysis has various advantages over typical genomics research. It creates a vast and varied spectrum of genetic material by combining the genetic data from all the sampled genomes. Comparing pan-genomics analysis to conventional genomic research, there are a number of benefits. Although the most recent era of pan-genomic studies has used cutting-edge sequencing technology to shed fresh light on biological variety and improvement, the potential uses of pan-genomics in improvement have not yet been fully realized. Pan-genome research in various organisms has demonstrated that missing genetic components and the detection of significant Structural Variants (SVs) can be investigated using pan-genomic methods. Many individual-specific sequences have been linked to biological adaptability, phenotypic, and key economic attributes. This study aims to focus on how pangenome analysis uncovers genetic differences in various organisms, including human, and their effects on phenotypes, as well as how this might help us comprehend the diversity of species. The review also concentrated on potential problems and the prospects for future pangenome research.

Unique genetic architecture of prolificacy in 'Sikkim Primitive' maize unraveled through whole-genome resequencing-based DNA polymorphism

KEY MESSAGE

'Sikkim Primitive' maize landrace, unique for prolificacy (7-9 ears per plant) possesses unique genomic architecture in branching and inflorescence-related gene(s), and locus Zm00001eb365210 encoding glycosyltransferases was identified as the putative candidate gene underlying QTL (qProl-SP-8.05) for prolificacy. The genotype possesses immense usage in breeding high-yielding baby-corn genotypes. 'Sikkim Primitive' is a native landrace of North Eastern Himalayas, and is characterized by having 7-9 ears per plant compared to 1-2 ears in normal maize. Though 'Sikkim Primitive' was identified in the 1960s, it has not been characterized at a whole-genome scale. Here, we sequenced the entire genome of an inbred (MGUSP101) derived from 'Sikkim Primitive' along with three non-prolific (HKI1128, UMI1200, and HKI1105) and three prolific (CM150Q, CM151Q and HKI323) inbreds. A total of 942,417 SNPs, 24,160 insertions, and 27,600 deletions were identified in 'Sikkim Primitive'. The gene-specific functional mutations in 'Sikkim Primitive' were classified as 10,847 missense (54.36%), 402 non-sense (2.015%), and 8,705 silent (43.625%) mutations. The number of transitions and transversions specific to 'Sikkim Primitive' were 666,021 and 279,950, respectively. Among all base changes, (G to A) was the most frequent (215,772), while (C to G) was the rarest (22,520). Polygalacturonate 4-α-galacturonosyltransferase enzyme involved in pectin biosynthesis, cell-wall organization, nucleotide sugar, and amino-sugar metabolism was found to have unique alleles in 'Sikkim Primitive'. The analysis further revealed the Zm00001eb365210 gene encoding glycosyltransferases as the putative candidate underlying QTL (qProl-SP-8.05) for prolificacy in 'Sikkim Primitive'. High-impact nucleotide variations were found in ramosa3 (Zm00001eb327910) and zeaxanthin epoxidase1 (Zm00001eb081460) genes having a role in branching and inflorescence development in 'Sikkim Primitive'. The information generated unraveled the genetic architecture and identified key genes/alleles unique to the 'Sikkim Primitive' genome. This is the first report of whole-genome characterization of the 'Sikkim Primitive' landrace unique for its high prolificacy.

A review of the pangenome: how it affects our understanding of genomic variation, selection and breeding in domestic animals?

As large-scale genomic studies have progressed, it has been revealed that a single reference genome pattern cannot represent genetic diversity at the species level. While domestic animals tend to have complex routes of origin and migration, suggesting a possible omission of some population-specific sequences in the current reference genome. Conversely, the pangenome is a collection of all DNA sequences of a species that contains sequences shared by all individuals (core genome) and is also able to display sequence information unique to each individual (variable genome). The progress of pangenome research in humans, plants and domestic animals has proved that the missing genetic components and the identification of large structural variants (SVs) can be explored through pangenomic studies. Many individual specific sequences have been shown to be related to biological adaptability, phenotype and important economic traits. The maturity of technologies and methods such as third-generation sequencing, Telomere-to-telomere genomes, graphic genomes, and reference-free assembly will further promote the development of pangenome. In the future, pangenome combined with long-read data and multi-omics will help to resolve large SVs and their relationship with the main economic traits of interest in domesticated animals, providing better insights into animal domestication, evolution and breeding. In this review, we mainly discuss how pangenome analysis reveals genetic variations in domestic animals (sheep, cattle, pigs, chickens) and their impacts on phenotypes and how this can contribute to the understanding of species diversity. Additionally, we also go through potential issues and the future perspectives of pangenome research in livestock and poultry.

Discovery of DNA polymorphisms via genome-resequencing and development of molecular markers between two barley cultivars

Genome resequencing uncovers genome-wide DNA polymorphisms that are useful for the development of high-density InDel markers between two barley cultivars. Discovering genomic variations and developing genetic markers are crucial for genetics studies and molecular breeding in cereal crops. Although InDels (insertions and deletions) have become popular because of their abundance and ease of detection, discovery of genome-wide DNA polymorphisms and development of InDel markers in barley have lagged behind other cereal crops such as rice, maize and wheat. In this study, we re-sequenced two barley cultivars, Golden Promise (GP, a classic British spring barley variety) and Hua30 (a Chinese spring barley variety), and mapped clean reads to the reference Morex genome, and identified in total 13,933,145 single nucleotide polymorphisms (SNPs) and 1,240,456 InDels for GP with Morex, 11,297,100 SNPs and 781,687 InDels for Hua30 with Morex, and 13,742,399 SNPs and 1,191,597 InDels for GP with Hua30. We further characterized distinct types, chromosomal distribution patterns, genome location, functional effect, and other features of these DNA polymorphisms. Additionally, we revealed the functional relevance of these identified SNPs/InDels regarding different flowering times between Hua30 and GP within 17 flowering time genes. Furthermore, we developed a series of InDel markers and validated them experimentally in 43 barley core accessions, respectively. Finally, we rebuilt population structure and phylogenetic tree of these 43 barley core accessions. Collectively, all of these genetic resources will facilitate not only the basic research but also applied research in barley.

Whole-Genome Sequencing and RNA-Seq Reveal Differences in Genetic Mechanism for Flowering Response between Weedy Rice and Cultivated Rice

Flowering is a key agronomic trait that influences adaptation and productivity. Previous studies have indicated the genetic complexity associated with the flowering response in a photoinsensitive weedy rice accession PSRR-1 despite the presence of a photosensitive allele of a key flowering gene Hd1. In this study, we used whole-genome and RNA sequencing data from both cultivated and weedy rice to add further insights. The de novo assembly of unaligned sequences predicted 225 genes, in which 45 were specific to PSRR-1, including two genes associated with flowering. Comparison of the variants in PSRR-1 with the 3K rice genome (RG) dataset identified unique variants within the heading date QTLs. Analyses of the RNA-Seq result under both short-day (SD) and long-day (LD) conditions revealed that many differentially expressed genes (DEGs) colocalized with the flowering QTLs, and some DEGs such as Hd1, OsMADS56, Hd3a, and RFT1 had unique variants in PSRR-1. Ehd1, Hd1, OsMADS15, and OsMADS56 showed different alternate splicing (AS) events between genotypes and day length conditions. OsMADS56 was expressed in PSRR-1 but not in Cypress under both LD and SD conditions. Based on variations in both sequence and expression, the unique flowering response in PSRR-1 may be due to the high-impact variants of flowering genes, and OsMADS56 is proposed as a key regulator for its day-neutral flowering response.