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At least 19 recordsLinked to original sources
PubMed2025

Beyond parental lines: multi-omics analyses reveal epigenetic and transcriptional mechanisms underlying heterosis in Oryza sativa × Oryza rufipogon hybrids.

Heterosis, or hybrid vigor, refers to the superior phenotypes of a hybrid compared with their parents and is widely exploited in agriculture. Interspecific hybrids within the Oryza genus demonstrate significant potential for the systematic improvement of rice varieties. Nevertheless, the mechanistic basis underlying heterosis in interspecific Oryza hybrids remains poorly understood. Here, we systematically performed phenotypic characterization, whole-genome bisulfite sequencing, RNA sequencing, and small RNA profiling using Oryza sativa L. ssp. japonica cv. Nipponbare (NIP), Oryza rufipogon Griff. acc. CWR, and their resulting F1 hybrid (named as NC). NIP and CWR showed distinct phenotypic and molecular differences. The interspecific hybrid, NC, exhibited significant yield heterosis. In the hybrid, most epigenetic and transcriptional features displayed additive inheritance patterns relative to parental lines. Analysis revealed that domestication-selected genes maintained relatively low DNA methylation coupled with high expression levels in both hybrid and parental lines. Additionally, we identified that non-additive miRNAs were potentially involved in regulating fertility, cell growth, and cell division processes in the hybrid. A significant negative correlation was observed between DNA methylation level and gene expression. Functional enrichment analysis revealed that hybrid-MPV DEGs were significantly associated with flowering time regulation, carbohydrate metabolism, photosynthesis, protein phosphorylation, seed development, and defense responses. Through weighted gene co-expression network analysis, we identified 102 functional gene modules, six of which were significantly associated with yield-related heterosis. Collectively, our results provide a multi-omics framework for understanding interspecific hybridization between elite cultivars and wild rice relatives, highlighting CWR as an untapped genetic reservoir for rice improvement.

Oryza↗
PubMed1975

The reaction of mitochondria in the coleoptiles of rice (Oryza sativa L.) with diaminobenzidine.

Diaminobenzidine, DAB, was applied to segments of aerobically and anaerobically grown coleoptiles of rice, Oryza sativa L., with the object of studying the location of cytochrome oxidase at the electron-microscope level. A specific staining of mitochondrial cristae and inner membrane was obtained, with no reaction in other organelles; with extended periods of incubation, the reaction product filled the mitochondria completely. In anaerobically grown coleoptiles, the reaction was much slower and the difference was particularly marked in vascular bundle companion cells and parenchyma, which gave the strongest reaction in aerobic tissue, but in the anaerobic stained even less than the cortical parenchyma. The reaction was inhibited by boiling and slowed very much by lowering of the incubation temperature from 27 to 4 degrees C. This indicated the involvement of an enzymic reaction and cyanide inhibition indicated that a haem enzyme was involved. The catalase inhibitor aminotriazole did not inhibit DAB oxidation. Nevertheless the specificity of the reaction for cytochrome oxidase must be questioned, because preheating of the tissue to 60 degrees C before incubation, which would be expected to destroy cytochrome oxidase activity, failed to decrease the oxidation, at least in aerobically grown coleoptiles. It is concluded that DAB is oxidized in the rice coleoptile tissue by a cytochrome system, and the development of this system is inhibited by anaerobiosis, but the oxidation cannot be claimed to represent cytochrome oxidase activity exclusively. Perhaps other autoxidizable, more heat-stable cytochromes participate in the reaction.

Aerobiosis↗
PubMed2025

Growth-limiting drought increases sensitivity of Asian rice (Oryza sativa) leaves to heat shock through physiological and spatially distinct transcriptomic responses.

Growth-limiting droughts (GLD) impair tissue expansion and delay developmental transitions but are often not considered as stressors, as many physiological traits are only slightly altered relative to well-watered counterparts. Concurrently, cell size, biochemical makeup, and transcriptome profiles vary along the leaf blade in accordance with the partitioning of distinct functions to spatially defined regions of the leaf. This suggests that because different parts of the leaf have underlying differences in their transcriptome profiles, they might respond to GLD in distinctive ways. Moreover, how antagonistic stressors influence physiology and gene expression in different zones of leaves is an open question. In this study, we profiled growth, anatomy, and gas exchange in Asian rice (Oryza sativa) leaves developed in well-watered and GLD conditions, with or without a secondary heat shock. We dissected leaves into seven equal-length segments for transcriptome analysis in these conditions. We hypothesized that GLD would make the leaves more sensitive to heat shock and would disrupt the underlying heterogeneity of the leaf transcriptome. GLD plants were more strongly affected by heat shock with respect to gas exchange and the number and types of genes that were differentially expressed and that these differences varied along the leaf blade. We developed an eFP browser tool with these data to facilitate exploration and hypothesis testing. These findings show that even mild drought treatments are sufficient to impact responses to antagonistic stressors and that substantial within-organ variance exists with respect to stress responses.

Oryza↗
PubMed1979

Protein quality in cereals and pulses. 1. Application of microbiological and other in vitro methods in the evaluation of rice (Oryza sativa L.), sorghum (Sorghum vulgare Pers.), barley and field beans (Vicia faba L.).

1. The Streptococcus zymogenes assay procedure was modified and used in the estimation of available methionine and relative nutritional value in rice (Oryza sativa L.), sorghum (Sorghum vulgare Pers.), barley and field beans (Vicia faba L.). The results were assessed in relation to the content of tannins and 'dye-binding lysine', and to published information on the nutritional quality of some of the test samples. 2. In grain of ten varieties of sorghum, for which other workers had reported a correlation (r -0.82; P less than 0.01) between tannin content and amino acid digestibility in chicks, the available methionine content ranged from 6.3 to 17.7 g/kg protein (nitrogen x 6.25) and was highly correlated with tannin content (r -0.97; P less than 0.001). The content of total methionine and dye-binding lysine varied little between varieties and was not related to tannin content. 3. In nine samples of rice the availability of methionine was uniformly high, in accordance with literature values for true digestibility of the N. 4. In field beans the presence of tammins in the seed coat was associated with a significant (P less than 0.001) reduction in the availability of methionine. In eleven tannin-free varieties the coefficient of availability averaged 0.791, compared with 0.685 in eleven tannin-containing varieties. The standard deviation associated with both values was 0.04. There was no such difference between the corresponding dye-binding lysine values. 5. Thirty-three samples of barley were examined, representing fourteen varieties, four of which had been grown at several widely different latitudes in England and Sweden. There was little difference in methionine content between samples. The average availability coefficient for eighteen samples grown in England was 0.995+/-0.044, and for fifteen varieties grown in Sweden it was 0.851+/-0.042. The difference was not associated with any difference in tannin content, which was uniformly low. The findings contradict published evidence for marked increase in tannin content with increase in geographical latitude of cultivation, associated with decrease in digestibility of N.

Biological Assay↗
PubMed1977

Mutagenic effect of argemone oil in Oryza sativa L.

In view of the large scale adulteration of edible oils with Argemone oil, a study was undertaken to test its mutagenicity on rice seed. In treatment with screw-pressed oil a marked reduction in seed germination and high chlorophyll mutation and mutant frequencies were observed. In sequential treatments between gamma rays and Argemone oil both mutation and mutant frequencies were significantly higher than that of individual treatments. This study clearly indicates that Argemone oil is a potent mutagen with serious implications for the genetic hygiene of human beings.

Mutagens↗
PubMed2025

Integrated transcriptomic, transcriptional factors, and protein interaction reveal the regulatory mechanisms of flowering time in rice (Oryza sativa L.).

Appropriate flowering time is important for rice regional adaptation and optimum rice production, but little is known about the omics of heading date in rice. Here, we studied omics including transcriptome, proteome and transcriptional factors to identify regulatory genes related to flowering time. A total of 1402 differentially expressed genes (DEGs, 721 up-regulated and 681 down-regulated) were detected in wild and mutant. These transcripts are classified according to biological processes, cellular components, and molecular functions. Among these differentially expressed genes, many transcription factor genes demonstrated multiple regulatory pathways involved in flowering time. Gene expression analysis showed that Os03g0122600 (OsMADS50), Os08g0105000 (Ehd3), Os06g0275000 (Hd1) were expressed higher and Os06g0199500 (OsHAL3), Os06g0498800 (OsMFT1), Os08g0105000 (Ehd3), Os06g0157700 (Hd3a), and Os02g0731700 (Ghd2), were expressed lower in wild compared to mutant, which are the key genes that regulate the flowering in rice. In addition, Ghd7 interacted with Os10g30860 and Os12g08260 using yeast two-hybrid assay. We identified 28 potential Ghd7 transcriptional regulators using the transcription factor-centered yeast one hybrid (TF-Centered Y1H) assay. Taken together, this study developed a new set of genomic resources to identify and characterize genes, proteins, and motifs associated with flowering time.

Oryza↗
PubMed2024

Sulfonamide-induced DNA hypomethylation disturbed sugar metabolism in rice (Oryza sativa L.).

DNA methylation is well-accepted as a bridge to unravel the complex interplay between genome and environmental exposures, and its alteration regulated the cellular metabolic responses towards pollutants. However, the mechanism underlying site-specific aberrant DNA methylation and metabolic disorders under pollutant stresses remained elusive. Herein, the multilevel omics interferences of sulfonamides (i.e., sulfadiazine and sulfamerazine), a group of antibiotics pervasive in farmland soils, towards rice in 14 days of 1 mg/L hydroponic exposure were systematically evaluated. Metabolome and transcriptome analyses showed that 57.1-71.4 % of mono- and disaccharides were accumulated, and the differentially expressed genes were involved in the promotion of sugar hydrolysis, as well as the detoxification of sulfonamides. Most differentially methylated regions (DMRs) were hypomethylated ones (accounting for 87-95 %), and 92 % of which were located in the CHH context (H = A, C, or T base). KEGG enrichment analysis revealed that CHH-DMRs in the promoter regions were enriched in sugar metabolism. To reveal the significant hypomethylation of CHH, multi-spectroscopic and thermodynamic approaches, combined with molecular simulation were conducted to investigate the molecular interaction between sulfonamides and DNA in different sequence contexts, and the result demonstrated that sulfonamides would insert into the minor grooves of DNA, and exhibited a stronger affinity with the CHH contexts of DNA compared to CG or CHG contexts. Computational modeling of DNA 3D structures further confirmed that the binding led to a pitch increase of 0.1 Å and a 3.8° decrease in the twist angle of DNA in the CHH context. This specific interaction and the downregulation of methyltransferase CMT2 (log2FC = -4.04) inhibited the DNA methylation. These results indicated that DNA methylation-based assessment was useful for metabolic toxicity prediction and health risk assessment.

DNA Methylation↗
PubMed2026

Alternatively spliced killer-protector system confers S19-mediated hybrid male sterility in rice.

Hybrid sterility limits the use of strong interspecific heterosis and S19 is a major locus that confers hybrid sterility between Oryza sativa (Asian cultivated rice) and Oryza glaberrima (African cultivated rice). However, the S19 is not yet cloned and its underlying mechanism remains elusive. In this study, we identify two closely linked genes (S19A1 and S19A7) specific to African rice allele that encode a killer-protector module at the S19 locus. Two alternatively spliced transcripts expressed from the killer gene S19A1 (S19A1.1 and S19A1.2) encode mitochondria-targeted cytotoxic proteins that cause toxicity diversity for somatic and/or gametic cell death, respectively. However, S19A7 interacts with S19A1.1 and S19A1.2, blocking their cytotoxic effect. Because the Asian rice S19 allele lacks S19A1 and S19A7, male gametes that carry this allele are selectively aborted in Asian-African F1 hybrids. Knockout of S19A1 can overcome S19-mediated hybrid sterility. Haplotype analysis reveals that the functional S19 allele is absent in non-AA-genome Oryza species and likely emerged in the O. barthii-O. glaberrima lineage through a multi-step evolutionary process. Our findings provide insight into the genetic mechanisms responsible for hybrid sterility between Asian and African rice and suggest genetic and biotechnological strategies for the use of interspecific heterosis in rice.

Oryza↗
PubMed1975

Reversible redistribution of phytochrome within the cell upon conversion to its physiologically active form.

The intracellular localization of phytochrome was seen in dark-grown oat (Avena sativa L., cv. Garry) and rice (Oryza sativa L., cv. unknown) shoots after various light treatments using an indirect peroxidase-antiperoxidase antibody labeling method. Phytochrome is generally distributed throughout the cytoplasm in cells of tissue that had not been exposed to light prior to fixation. Within, at most, 8 min after the onset of saturating red irradiation, phytochrome, now present in the far-red-absorbing form, becomes associated with discrete regions of the cell. These regions do not appear to be nuclei, plastids, or mitochondria. After phototransformation back to the red-absorbing form originally present, phytochrome slowly resumes its general distribution. It is possible that this discrete localization of the far-red-absorbing form of phytochrome represents a physiologically significant binding with a receptor site in the cell.

Cytoplasm↗
PubMed2026

Heat stress impact on rice reproductive processes: challenges and new approaches.

Heat stress represents one of the most severe abiotic constraints to rice (Oryza sativa L.) productivity and is expected to intensify under ongoing climate change, particularly affecting the reproductive phase and leading to substantial yield and grain quality losses. This review synthesizes current knowledge on the impacts of heat stress on rice reproduction, with a focus on both male and female reproductive structures and their interactions. Evidence from anatomical, physiological, transcriptomic, and metabolomic studies to describe how elevated temperatures disrupt key reproductive processes, including microsporogenesis, anther dehiscence, pollen viability, pollen-pistil interactions, fertilisation, and embryo sac development were integrated in this review. It further discusses the genotype-dependent differences in reproductive thermotolerance; and key genes, metabolites, and pathways associated with heat stress perception, signalling, and tolerance are highlighted. Finally, it is briefly discussed how recent advances in breeding strategies, functional genomics and genome-editing technologies, particularly CRISPR-based approaches, are providing new opportunities to enhance reproductive resilience to heat stress and how it is essential to close the existing molecular knowledge gaps in the development of heat-tolerant rice varieties capable of sustaining productivity in a warming climate.

Oryza sativa (L.)↗
PubMed2026

Hormone priming and metabolic engineering of phytohormone crosstalk in rice under combined biotic and abiotic stresses: a multi-omics perspective for climate-resilient crop development.

Rice (Oryza sativa L.) is the caloric backbone for more than half of humanity, yet it remains one of the most vulnerable crops to the simultaneous biotic and abiotic stresses exacerbated by climate change. Phytohormone priming and the complex crosstalk networks governed by transcription factor hubs like WRKY, MYB, and NAC serve as the central adaptive mechanism for stress resilience. This review synthesizes how multi-omics integration, including spatial and single-cell transcriptomics, is resolving the molecular architecture of hormonal priming and epigenetic stress memory. We critically evaluate advanced metabolic engineering and genome-editing strategies such as CRISPR-Cas9, base/prime editing, and synthetic gene circuits that enable precision modifications to decouple stress tolerance from historical yield penalties. Furthermore, we discuss the emerging roles of microbiome-assisted priming via synthetic consortia and the application of artificial intelligence and digital twins (continuously updated computational models of crop physiology) for predictive stress management. By integrating these diverse technological pillars, we propose a systems-level roadmap for developing climate-resilient rice cultivars capable of maintaining yield stability across a volatile combinatorial stress landscape. This synthesis provides a framework for translating mechanistic hormonal insights into field-applicable cultivars to ensure global food security.

CRISPR↗
PubMed2025

A six-repeat PPR protein WPR directly binds target RNAs and coordinates chloroplast RNA processing via dual recruitment of MORF1, MORF8b, and CAF2 proteins in rice.

Pentatricopeptide repeat (PPR) proteins are key regulators of organelle RNA metabolism in plants, yet their precise mechanisms in chloroplast RNA processing remain unclear. Here, we identify WPR, a unique P-type PPR protein in rice (Oryza sativa L.), as a critical factor in chloroplast RNA splicing and editing. A ~112-kb chromosomal inversion upstream of WPR causes an albino panicle rachis phenotype (wpr mutant), while complete loss of WPR function leads to seedling lethality. WPR deficiency disrupts the splicing of multiple group II introns (atpF, ndhA, ndhB, petB, rpl2, and rps12) and impairs RNA editing in transcripts such as ndhA, ndhB, ndhG, rps14, and ycf3. Electrophoretic mobility shift assay (EMSA) data confirm that WPR directly binds to precursor mRNAs of atpF, ndhA, petB, rpl2, and rps12. Strikingly, WPR interacts with both RNA editing factors (MORF1, MORF8b) and the splicing factor CAF2, but not with other PPR proteins targeting the same transcripts. Unlike most PPR proteins, WPR contains only six PPR repeats, which is the fewest among all functionally characterized rice PPR proteins. With few informative repeats, WPR likely possesses a broad, low-specificity RNA-binding activity. Moreover, WPR may act on chloroplast RNA maturation by recruiting MORFs and CAF2 rather than other PPR proteins, highlighting a novel regulatory mode in which P-type PPR protein may act as an RNA-binding scaffold to integrate diverse RNA-processing machineries. This study advances the understanding of PPR protein diversity and provides new insights into the molecular mechanisms of chloroplast RNA processing in rice.

Oryza↗
PubMed2026

Genomic Footprints of Historical Introgression Between Ancient Lineages of Wild Oryza AA-Genome Species With Widely Separated Contemporary Distributions.

Phylogenetic incongruence is increasingly recognized as pervasive, yet the extent to which reticulate evolution occurs between groups separated by substantial geographical distances and deep phylogenetic divergence remains poorly characterized. In the Oryza AA-genome group-a model for plant speciation and domestication-the traditional bifurcation model posits that Australian Oryza meridionalis and African Oryza longistaminata occupy basal branches, distinct from the more recently diversified monophyletic clade comprising Asian and other African lineages, including major cultivars. However, recent evidence from endogenous viral sequences has hinted at unexpected genetic relatedness between African O. longistaminata and Asian Oryza sativa, which are geographically and phylogenetically distant. Here, we conducted a genome-wide survey across 11 Oryza species to systematically identify genomic regions exhibiting phylogenetic incongruence. Widespread phylogenetic discordance was observed, notably involving genomic segments in which O. longistaminata showed phylogenetic proximity to Asian species, contradicting their established deep divergence. To distinguish between introgression and incomplete lineage sorting, we performed four-taxon ABBA-BABA tests, which provided statistical support for introgression. Furthermore, divergence time estimates for these incongruent regions were younger than the species divergence times, suggesting historical introgression between the ancestors of lineages that are currently separated by vast geographical distances. Systematic assessments indicated that potential analytical artifacts, such as compositional bias and substitution saturation, were unlikely to explain the observations. These convergent lines of evidence suggest that ancient introgression had occurred between currently geographically separated and evolutionarily divergent Oryza lineages, leaving detectable footprints across their modern genomes.

Oryza↗
PubMed2026

Two domesticated species of rice shaped the population structure of Xanthomonas oryzae pv. oryzae in Africa.

African rice (Oryza glaberrima) was independently domesticated in West Africa around 3000 years ago, and has long been intertwined in the history of the region. Asian rice (Oryza sativa), which was introduced in Africa when European settlers arrived, gradually replaced African rice and has since dominated rice cultivation in the continent. Domesticated rice species are affected by bacterial leaf blight (BLB), which is caused by the pathogen Xanthomonas oryzae pv. oryzae (Xoo). Here we show that the bacterial leaf blight pathogen in Africa (AfXoo) belongs to a distinct phylogroup from the one circulating in Asia (AsXoo), and has a different evolutionary history. Analysis of 87 AfXoo genomes identified five main populations, including highly clonal ones, and a more diverse and recombinant population. Tip-dating analysis revealed that the AfXoo population went through a period of expansion, then decline and more recent recovery. We hypothesize this followed the rise and fall of African rice, and that the introduction of O. sativa served as a bottleneck leading to the emergence of current AfXoo populations. We show that AfXoo has a highly conserved repertoire of type III effectors (T3E), but that nonetheless there is variation especially between populations. In the case of transcription activator-like effectors (TALEs), variation can arise quickly through rearrangements, and we hypothesize that the TALE repertoire of AfXoo has been selected to allow the bacteria to colonize both species of cultivated rice found in the continent. Our research provides an attempt to decipher the genetic history of bacterial blight in West Africa, and its past and present impact on rice cultivation in the region.

Journal Article↗
PubMed1977

Factors modifying radiation induced stimulation in plants: pre-irradiation seed moisture content.

The effect of moisture content of seeds at the time of irradiation in relation to radiation-induced stimulation was investigated on rice (Oryza sativa c.v. D-6-2-2). The optimum moisture content was 8% for stimulation measured as seedling height. It is concluded that seed moisture at the time of irradiation plays an important role in the expression of stimulation and its reproducibility.

Cobalt Radioisotopes↗