Transcriptomic analysis of salt-tolerant and sensitive high-yield japonica rice (Oryza sativa L.) reveals complicated salt-tolerant mechanisms.

Developing and cultivating rice varieties is a potent strategy for reclaiming salinity-affected soils for rice production. Nevertheless, the molecular mechanisms conferring salt tolerance, especially in conventional high-yield japonica rice varieties, remain obscure. In this study, Zhendao 23309 (ZD23309) exhibited significantly less grain yield reduction under a salt stress gradient than the control variety Wuyunjing 30 (WYJ30). High positive correlations between grain yield and dry matter accumulation at the jointing, heading and maturity stages indicated that early salt tolerance performance is a crucial hallmark for yield formation. After a mild salt stress (85 mM NaCl) of young seedlings, RNA sequencing (RNA-seq) of shoot and root separately identified a total of 1952 and 3647 differentially expressed genes (DEGs) in ZD23309, and 2114 and 2711 DEGs in WYJ30, respectively. Gene ontology (GO) analysis revealed numerous DEGs in ZD23309 that play pivotal roles in strengthening salt tolerance, encompassing the response to stimulus (GO:0050896) in shoots and nucleoside binding (GO:0001882) in roots. Additionally, distinct expression patterns were observed in a fraction of genes in the two rice varieties under salt stress, corroborating the efficacy of previously reported salt tolerance genes. Our research not only offers fresh insights into the differences in salt stress tolerance among conventional high-yield rice varieties but also unveils the intricate nature of salt tolerance mechanisms. These findings lay a solid groundwork for deciphering the mechanisms underlying salt tolerance.

CRISPR-Cas9-mediated deletion of carbonic anhydrase 2 in the ciliary body to treat glaucoma.

The carbonic anhydrase 2 (Car2) gene encodes the primary isoenzyme responsible for aqueous humor (AH) production and plays a major role in the regulation of intraocular pressure (IOP). The CRISPR-Cas9 system, based on the ShH10 adenovirus-associated virus, can efficiently disrupt the Car2 gene in the ciliary body. With a single intravitreal injection, Car2 knockout can significantly and sustainably reduce IOP in both normal mice and glaucoma models by inhibiting AH production. Furthermore, it effectively delays and even halts glaucomatous damage induced by prolonged high IOP in a chronic ocular hypertension model, surpassing the efficacy of clinically available carbonic anhydrase inhibitors such as brinzolamide. The clinical application of CRISPR-Cas9 based disruption of Car2 is an attractive therapeutic strategy that could bring additional benefits to patients with glaucoma.

Diagnostic performance of wide-field optical coherence tomography angiography in detecting open-angle glaucoma in high myopia.

PURPOSE: To compare the diagnostic performance of the capillary density (CD) of the central 1-6 mm and peripheral 6-12 mm annular regions in detecting open-angle glaucoma in high myopia (HM) using 15 × 12 mm wide-field swept-source optical coherence tomography angiography (WF SS-OCTA). METHODS: The study enrolled 206 and 103 eyes with HM and highly myopic open-angle glaucoma (HM-OAG), respectively. WF SS-OCTA images centred on the fovea were obtained to analyse the changes in the CD in the 1-3 mm, 3-6 mm, 6-9 mm, and 9-12 mm annular regions. CD of the superficial capillary plexus (SCP) was measured with the built-in software. The area under the receiver operating characteristic curve (AUROC) of each region was compared. RESULTS: The diagnostic performance of the SCP CD in the central 1-6 mm annular region (AUROC = 0.849) was better than that in the peripheral 6-12 mm annular region (AUROC = 0.756, p = 0.001). The annular AUROCs of SCP CD peaked in the 3-6 mm annular region (AUROC = 0.858) and gradually decreased with increasing diameter and were lower than the corresponding AUROCs of the ganglion cell-inner plexiform layer thickness (p < 0.05 for all comparisons). SCP CD of the inferior quadrant in the 3-6 mm annular region had the best diagnostic performance (AUROC = 0.859). CONCLUSION: The SCP CD in the central 1-6 mm annular region exhibited better diagnostic performance for the detection of HM-OAG in HM. The assessment of more peripheral regions has no added value in detecting glaucoma in HM.

Phase-Change Based Oxygen Carriers Improve Acute Cerebral Hypoxia.

Stroke is the second leading cause of death worldwide, and hypoxia is a major crisis of the brain after stroke. Therefore, providing oxygen to the brain microenvironment can effectively protect neurons from damage caused by cerebral hypoxia. However, there is a lack of timely and effective means of oxygen delivery clinically to the brain for acute cerebral hypoxia. Here, a phase-change based nano oxygen carrier is reported, which can undergo a phase change in response to increasing temperature in the brain, leading to oxygen release. The nano oxygen carrier demonstrate intracerebral oxygen delivery capacity and is able to release oxygen in the hypoxic and inflammatory region of the brain. In the acute ischemic stroke mouse model, the nano oxygen carrier can effectively reduce the area of cerebral infarction and decrease the level of inflammation triggered by cerebral hypoxia. By taking advantage of the increase in temperature during cerebral hypoxia, phase-change oxygen carrier proposes a new intracerebral oxygen delivery strategy for reducing acute cerebral hypoxia.

Toward breeding pigmented rice balancing nutrition and yield.

A recent study by Sedeek et al. provides multiomic resources that illustrate the genetic diversity, metabolites, elemental composition, and the possibility of agronomic trait improvement, through genome-editing technology, for nutrient-rich pigmented rice. This will guide future rice breeding programs for balancing optimal agronomic traits and excellent nutritional quality.

Pijx confers broad-spectrum seedling and panicle blast resistance by promoting the degradation of ATP ß subunit and OsRbohC-mediated ROS burst in rice.

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most important diseases of rice. Utilization of blast-resistance genes is the most economical, effective, and environmentally friendly way to control the disease. However, genetic resources with broad-spectrum resistance (BSR) that is effective throughout the rice growth period are rare. In this work, using a genome-wide association study, we identify a new blast-resistance gene, Pijx, which encodes a typical CC-NBS-LRR protein. Pijx is derived from a wild rice species and confers BSR to M. oryzae at both the seedling and panicle stages. The functions of the resistant haplotypes of Pijx are confirmed by gene knockout and overexpression experiments. Mechanistically, the LRR domain in Pijx interacts with and promotes the degradation of the ATP synthase ß subunit (ATPb) via the 26S proteasome pathway. ATPb acts as a negative regulator of Pijx-mediated panicle blast resistance, and interacts with OsRbohC to promote its degradation. Consistently, loss of ATPb function causes an increase in NAPDH content and ROS burst. Remarkably, when Pijx is introgressed into two japonica rice varieties, the introgression lines show BSR and increased yields that are approximately 51.59% and 79.31% higher compared with those of their parents in a natural blast disease nursery. In addition, we generate PPLPijx Pigm and PPLPijx Piz-t pyramided lines and these lines also have higher BSR to panicle blast compared with Pigm- or Piz-t-containing rice plants. Collectively, this study demonstrates that Pijx not only confers BSR to M. oryzae but also maintains high and stable rice yield, providing new genetic resources and molecular targets for breeding rice varieties with broad-spectrum blast resistance.

A de novo evolved gene contributes to rice grain shape difference between indica and japonica.

The role of de novo evolved genes from non-coding sequences in regulating morphological differentiation between species/subspecies remains largely unknown. Here, we show that a rice de novo gene GSE9 contributes to grain shape difference between indica/xian and japonica/geng varieties. GSE9 evolves from a previous non-coding region of wild rice Oryza rufipogon through the acquisition of start codon. This gene is inherited by most japonica varieties, while the original sequence (absence of start codon, gse9) is present in majority of indica varieties. Knockout of GSE9 in japonica varieties leads to slender grains, whereas introgression to indica background results in round grains. Population evolutionary analyses reveal that gse9 and GSE9 are derived from wild rice Or-I and Or-III groups, respectively. Our findings uncover that the de novo GSE9 gene contributes to the genetic and morphological divergence between indica and japonica subspecies, and provide a target for precise manipulation of rice grain shape.

Genetic Diversification of Starch Branching Enzymes during Maize Domestication and Improvement.

Elucidating the genetic basis of starch pasting and gelatinization properties is crucial for enhancing the quality of maize and its utility as feed and industrial raw material. In maize, ZmSBE genes encode important starch branching enzymes in the starch biosynthesis pathway. In this study, we re-sequenced the genomic sequences of ZmSBEI, ZmSBEIIa, ZmSBEIIb, and ZmSBEIII in three lines called 335 inbred lines, 68 landrace lines, and 32 teosinte lines. Analyses of nucleotide polymorphisms and haplotype diversity revealed differences in the selection patterns of ZmSBEI, ZmSBEIIa, ZmSBEIIb, and ZmSBEIII during maize domestication and improvement. A marker-trait association analysis of inbred lines detected 22 significant loci, including 18 SNPs and 4 indels significantly associated with three maize starch physicochemical properties. The allele frequencies of two variants (SNP17249C and SNP5055G) were examined in three lines. The frequency of SNP17249C in ZmSBEIIb was highest in teosinte lines, followed by landrace lines, and inbred lines, whereas there were no significant differences in the frequency of SNP5055G in ZmSBEIII among the three lines. These results suggest that ZmSBE genes play an important role in the phenotypic variations in the starch physicochemical properties in maize. The genetic variants detected in this study may be used to develop functional markers for improving maize starch quality.

Expression of Th1/2/17 Cytokines in CML with or without Pulmonary Bacterial and Fungal Coinfection.

Background: Tyrosine kinase inhibitors (TKIs) are the standard therapy for patients with chronic myeloid leukemia (CML). While their use greatly increases patient survival rates and can lead to normal life expectancy, bacterial infections in the lungs continue to play a significant role in determining patient outcomes. Methods: In this study, the medical records of 272 CML and 53 healthy adults were analyzed. Information on age, sex, body temperature, procalcitonin (PCT), C-reactive protein (CRP), and cytokine levels were collected from patients. Since the data belonged to a nonstate distribution, we used the Mann-Whitney U test to examine differences between groups. Cut-off values were analyzed by receiver operating characteristic (ROC) curves. Results: No significant differences in the Th1/2/17 levels were observed in relation to TKI treatment. Further analysis showed that the levels of the interleukins IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-22, IL-12p70, IL-17A, IL-17F, and IL-1ß, interferon (IFN-γ), and tumor necrosis factors (TNF α and ß) were higher in patients with pulmonary bacterial infections compared with uninfected patients. IL-6, IL-8, and IL-10 levels in CML patients with bacterial and fungal coinfection were higher than those in patients without infection. The areas under the ROC curves (AUCs) were found to be 0.73 for IL-5, 0.84 for IL-6, 0.82 for IL-8, 0,71 for IL-10, and 0.84 for TNF-α. AUC values were higher for patients with pulmonary bacterial infection, especially IL-6 (AUC = 0.84, cut-off = 13.78 pg/ml) and IL-8 (AUC = 0.82, cut-off = 14.35 pg/ml), which were significantly better than those for CRP (AUC = 0.80, cut-off = 6.18 mg/l), PCT (AUC = 0.71, cut-off = 0.25 ng/ml), and body temperature (AUC = 0.68, cut-off = 36.8°C). In addition, according to the cut-off values, we found that 83.33% of patients with pulmonary bacterial infections had IL-6 ≥ 13.78 pg/ml, while when IL-6, IL-8, and IL-10 levels simultaneously exceeded the cut-off values, the probability of pulmonary bacterial infection was 93.55%. Conclusions: TKI treatment did not appear to affect cytokine expression in CML patients. However, CML patients with pulmonary bacterial infection had significantly higher levels of Th1/2/17 cytokines. In particular, abnormally elevated IL-6, IL-8, and IL-10 levels were associated with a pulmonary bacterial infection in patients with CML.

Cytokines help suggest aplastic anemia with pulmonary bacterial or co-fungal infection.

Although aplastic anemia (AA) does not come under the category of blood malignant diseases, the infection that frequently occurs in this bone marrow failure can make it worse. Pulmonary infection is the most prevalent but limiting clinical diagnosis. To find biomarkers predicting bacterial or bacterial-combined fungal infections in the lungs, we reviewed 287 AA medical records including 151 without any infection, 87 with pure pulmonary bacterial infection, and 49 with bacterial and fungal infection were reviewed. There were substantial changes in IL-17F, IL-17A, IFN-γ, IL-6, IL-8, and IL-10 levels between the non-infected and lung bacterial infection groups (P < 0.05). Further, a significant variation in IL-17A, TNF-ß, IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IL-22, and IL-12p70, between the uninfected group and the pulmonary bacterial and fungal infection group (P < 0.05) was observed. The results further revealed significant differences in TNF-ß, IL-12p70, IL-6, IL-8, and IL-10 between the pulmonary bacterial infection group and the fungal infection group (P < 0.05). Moreover, by calculating ROC and cut-off values, we determined that IL-6 (AUC = 0.98, Cut-off = 14.28 pg/ml, P = 0.0000) had a significant advantage than other cytokines, body temperature (AUC = 0.61, P = 0.0050), PCT (AUC = 0.57, P = 0.0592), and CRP (AUC = 0.60, P = 0.0147) in the detection of lungs bacterial infections. In addition, IL-6 (AUC = 1.00, Cut-off = 51.50 pg/ml, P = 0.000) and IL-8 (AUC = 0.87, Cut-off = 60.53 pg/ml, P = 0.0000) showed stronger advantages than other cytokines, body temperature (AUC = 0.60, P = 0.0324), PCT (AUC = 0.72, Cut-off = 0.63 ng/ml, P = 0.0000) and CRP (AUC = 0.79, Cut-off = 5.79 mg/l, P = 0.0000) in distinguishing bacteria from fungi. This may suggest that IL-8 may play a role in differentiating co-infected bacteria and fungi. Such advantages are repeated in severe aplastic anemia (SAA) and very severe aplastic anemia (VSAA).In conclusion, aberrant IL-6 elevations in AA patients may predict the likelihood of bacterial lung infection. The concurrent increase of IL-6 and IL-8, on the other hand, should signal bacterial and fungal infections in patients.These findings may help to suggest bacterial or fungal co-infection in patients with AA (Focus on VSAA and SAA).

BMSC-derived exosomal miR-27a-3p and miR-196b-5p regulate bone remodeling in ovariectomized rats.

Background: In the bone marrow microenvironment of postmenopausal osteoporosis (PMOP), bone marrow mesenchymal stem cell (BMSC)-derived exosomal miRNAs play an important role in bone formation and bone resorption, although the pathogenesis has yet to be clarified. Methods: BMSC-derived exosomes from ovariectomized rats (OVX-Exo) and sham-operated rats (Sham-Exo) were co-cultured with bone marrow-derived macrophages to study their effects on osteoclast differentiation. Next-generation sequencing was utilized to identify the differentially expressed miRNAs (DE-miRNAs) between OVX-Exo and Sham-Exo, while target genes were analyzed using bioinformatics. The regulatory effects of miR-27a-3p and miR-196b-5p on osteogenic differentiation of BMSCs and osteoclast differentiation were verified by gain-of-function and loss-of-function analyses. Results: Osteoclast differentiation was significantly enhanced in the OVX-Exo treatment group compared to the Sham-Exo group. Twenty DE-miRNAs were identified between OVX-Exo and Sham-Exo, among which miR-27a-3p and miR-196b-5p promoted the expressions of osteogenic differentiation markers in BMSCs. In contrast, knockdown of miR-27a-3p and miR-196b-5p increased the expressions of osteoclastic markers in osteoclast. These 20 DE-miRNAs were found to target 11435 mRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these target genes were involved in several biological processes and osteoporosis-related signaling pathways. Conclusion: BMSC-derived exosomal miR-27a-3p and miR-196b-5p may play a positive regulatory role in bone remodeling.

GWAS and Transcriptome Analysis Reveal Key Genes Affecting Root Growth under Low Nitrogen Supply in Maize.

Nitrogen (N) is one of the most important factors affecting crop production. Root morphology exhibits a high degree of plasticity to nitrogen deficiency. However, the mechanisms underlying the root foraging response under low-N conditions remain poorly understood. In this study, we analyzed 213 maize inbred lines using hydroponic systems and regarding their natural variations in 22 root traits and 6 shoot traits under normal (2 mM nitrate) and low-N (0 mM nitrate) conditions. Substantial phenotypic variations were detected for all traits. N deficiency increased the root length and decreased the root diameter and shoot related traits. A total of 297 significant marker-trait associations were identified by a genome-wide association study involving different N levels and the N response value. A total of 51 candidate genes with amino acid variations in coding regions or differentially expressed under low nitrogen conditions were identified. Furthermore, a candidate gene ZmNAC36 was resequenced in all tested lines. A total of 38 single nucleotide polymorphisms and 12 insertions and deletions were significantly associated with lateral root length of primary root, primary root length between 0 and 0.5 mm in diameter, primary root surface area, and total length of primary root under a low-N condition. These findings help us to improve our understanding of the genetic mechanism of root plasticity to N deficiency, and the identified loci and candidate genes will be useful for the genetic improvement of maize tolerance cultivars to N deficiency.

Genetic and molecular factors in determining grain number per panicle of rice.

It was suggested that the most effective way to improve rice grain yield is to increase the grain number per panicle (GN) through the breeding practice in recent decades. GN is a representative quantitative trait affected by multiple genetic and environmental factors. Understanding the mechanisms controlling GN has become an important research field in rice biotechnology and breeding. The regulation of rice GN is coordinately controlled by panicle architecture and branch differentiation, and many GN-associated genes showed pleiotropic effect in regulating tillering, grain size, flowering time, and other domestication-related traits. It is also revealed that GN determination is closely related to vascular development and the metabolism of some phytohormones. In this review, we summarize the recent findings in rice GN determination and discuss the genetic and molecular mechanisms of GN regulators.

Primary root response to combined drought and heat stress is regulated via salicylic acid metabolism in maize.

The primary root is the first organ to perceive the stress signals for abiotic stress. In this study, maize plants subjected to drought, heat and combined stresses displayed a significantly reduced primary root length. Metabolic and transcriptional analyses detected 72 and 5,469 differentially expressed metabolites and genes in response to stress conditions, respectively. The functional annotation of differentially expressed metabolites and genes indicated that primary root development was mediated by pathways involving phenylalanine metabolism, hormone metabolism and signaling under stress conditions. Furthermore, we found that the concentration of salicylic acid and two precursors, shikimic acid and phenylalanine, showed rapid negative accumulation after all three stresses. The expression levels of some key genes involved in salicylic acid metabolism and signal transduction were differentially expressed under stress conditions. This study extends our understanding of the mechanism of primary root responses to abiotic stress tolerance in maize.

Nucleotide polymorphisms of the maize ZmFWL7 gene and their association with ear-related traits.

Plant fw2.2-like (FWL) genes, encoding proteins harboring a placenta-specific eight domain, have been suggested to control fruit and grain size through regulating cell division, differentiation, and expansion. Here, we re-sequenced the nucleotide sequences of the maize ZmFWL7 gene, a member of the FWL family, in 256 elite maize inbred lines, and the associations of nucleotide polymorphisms in this locus with 11 ear-related traits were further detected. A total of 175 variants, including 159 SNPs and 16 InDels, were identified in the ZmFWL7 locus. Although the promoter and downstream regions showed higher nucleotide polymorphism, the coding region also possessed 61 SNPs and 6 InDels. Eleven polymorphic sites in the ZmFWL7 locus were found to be significantly associated with eight ear-related traits. Among them, two nonsynonymous SNPs (SNP2370 and SNP2898) showed significant association with hundred kernel weight (HKW), and contributed to 7.11% and 8.62% of the phenotypic variations, respectively. In addition, the SNP2898 was associated with kernel width (KW), and contributed to 7.57% of the phenotypic variations. Notably, the elite allele T of SNP2370 was absent in teosintes and landraces, while its frequency in inbred lines was increased to 12.89%. By contrast, the frequency of the elite allele A of SNP2898 was 3.12% in teosintes, and it was raised to 12.68% and 19.92% in landraces and inbred lines, respectively. Neutral tests show that this locus wasn't artificially chosen during the process of domestication and genetic improvement. Our results revealed that the elite allelic variants in ZmFWL7 might possess potential for the genetic improvement of maize ear-related traits.

Increased Cytokine Levels Assist in the Diagnosis of Respiratory Bacterial Infections or Concurrent Bacteremia in Patients With Non-Hodgkin's Lymphoma.

Non-Hodgkin's lymphoma (NHL) is a form of tumor that originates in the lymphoid tissues. Bacterial infections are very common in NHL patients. Because most of the patients do not experience apparent symptoms during the initial stage of infection, it is difficult to detect the underlying condition before it progresses to a more critical level. The activation of the cytokines is a hallmark of inflammation. Due to the advantages of short detection time and high sensitivity of cytokines, many studies have focused on relationship between cytokines and infection. However, few studies have been conducted on NHL patients with infection. Therefore, we reviewed the cytokine profiles of 229 newly diagnosed NHL patients and 40 healthy adults to predict respiratory bacterial infection and bacteremia. Our findings revealed that IL-6(41.67 vs 9.50 pg/mL), IL-8(15.55 vs 6.61 pg/mL), IL-10(8.02 vs 4.52 pg/mL),TNF-ß(3.82 vs 2.96 pg/mL), IFN- γ(4.76 vs 2.96 pg/mL), body temperature(37.6 vs 36.5°C), CRP(20.80 vs 4.37 mg/L), and PCT(0.10 vs 0.04 ng/mL) levels were considerably greater in NHL cases with respiratory bacterial infections relative to NHL cases without infection (P<0.05). Furthermore, IL-6(145.00 vs 41.67 pg/mL), IL-8(34.60 vs 15.55 pg/mL),temperature(38.4 vs 37.6°C), PCT(0.79 vs 0.10 ng/mL), and CRP(93.70 vs 20.80 mg/L) levels in respiratory infectious NHL patients with more severe bacteremia were considerably elevated than in patients with respiratory bacterial infections only (P<0.05). Remarkably, increased levels of IL-6 and IL-8 are effective in determining whether or not pulmonary bacterial infectious NHL patients have bacteremia. Temperature, PCT, and CRP all have lower sensitivity and specificity than IL-6. IL-6 ≥18.79pg/mL indicates the presence of pulmonary bacterial infection in newly diagnosed NHL patients, and IL-6 ≥102.6pg/mL may suggest pulmonary bacterial infection with bacteremia. In short, this study shows that cytokines can be advantageous in the diagnosis and differentiation of pulmonary bacterial infection and bacteremia in newly diagnosed NHL patients and may also guide for the use of clinical antibiotics.

The plant streptolysin S (SLS)-associated gene B confers nitroaromatic tolerance and detoxification.

Nitroaromatic compounds, as the important chemical feedstock, have caused widespread environmental contaminations, and exhibited high toxicity and mutagenic activity to nearly all living organisms. The clean-up of nitroaromatic-contaminated soil and water has long been a major international concern. Here, we uncovered the role of a novel nitroreductase family gene, streptolysin S (SLS)-associated gene B (SagB), in enhancing nitroaromatic tolerance and detoxification of plants, and its potential application in phytoremediation of nitroaromatic contaminations. The expression of both the Arabidopsis and rice SagB genes is significantly induced by multiple hazardous nitroaromatic substances, including explosive pollutant 2,4,6-trinitrotoluene (TNT), natural compound 1-nitropyrene (1-NP) and herbicide pendimethalin (Pen). In vitro and in vivo evidences revealed that plant SagBs possess activities in degradation of these nitroaromatic substances. Arabidopsis and rice transgenic assays suggested that plant SagB genes increase tolerance and detoxification of nitroaromatic through facilitating its transformation to the amino derivative. More importantly, overexpression of plant SagBs increase their ability in TNT uptake, and remove more TNT from the growth culture. Our findings shed novel insights into a plant endogenous nitroreductase-mediated nitroaromatic tolerance and detoxification, and provide a new gene target for phytoremediation of nitroaromatic-contaminated environments.

OsCOMT, encoding a caffeic acid O-methyltransferase in melatonin biosynthesis, increases rice grain yield through dual regulation of leaf senescence and vascular development.

Melatonin, a natural phytohormone in plants, plays multiple critical roles in plant growth and stress responses. Although melatonin biosynthesis-related genes have been suggested to possess diverse biological functions, their roles and functional mechanisms in regulating rice grain yield remain largely unexplored. Here, we uncovered the roles of a caffeic acid O-methyltransferase (OsCOMT) gene in mediating rice grain yield through dual regulation of leaf senescence and vascular development. In vitro and in vivo evidence revealed that OsCOMT is involved in melatonin biosynthesis. Transgenic assays suggested that OsCOMT significantly delays leaf senescence at the grain filling stage by inhibiting degradation of chlorophyll and chloroplast, which, in turn, improves photosynthesis efficiency. In addition, the number and size of vascular bundles in the culms and leaves were significantly increased in the OsCOMT-overexpressing plants, while decreased in the knockout plants, suggesting that OsCOMT plays a positive role in vascular development of rice. Further evidence indicated that OsCOMT-mediated vascular development might owe to the crosstalk between melatonin and cytokinin. More importantly, we found that OsCOMT is a positive regulator of grain yield, and overexpression of OsCOMT increase grain yield per plant even in a high-yield variety background, suggesting that OsCOMT can be used as an important target for enhancing rice yield. Our findings shed novel insights into melatonin-mediated leaf senescence and vascular development and provide a possible strategy for genetic improvement of rice grain yield.