Rice Protein Research Articles

Steam cooking drives alterations of proteomics, protein structural and functional properties in rice (Oryza sativa l.)

Rice, as an important staple food consumed by people, is gradually becoming a concern for many consumers in terms of its eating quality. Many studies have found that protein is an important factor to determine the edible quality of rice. However, the protein changes during rice cooking have not been compared and studied in detail. In this study, the structural and functional characteristics of rice proteins before and after steaming were comprehensively compared. Meanwhile, proteomic strategies were also applied to analyze changes in protein composition and expression. Steaming promoted the aggregation of cooked rice proteins, resulting in a more compact structure and a significant increase in particle size (raw rice, 304.33 nm; cooked rice, 565.17 nm). Compared with raw rice protein (43.33%; 133.91%), the solubility (22.29%) and foaming capacity (119.53%) of cooked rice protein were significantly reduced, while emulsion activity was slightly improved. The differential abundance proteins were found to be predominantly down-regulated after steaming (238 proteins) and mostly enriched in metabolic pathways. The steaming process of rice mainly involves oxidative phosphorylation, thiamine metabolism, ether lipid metabolism, glycerophospholipid metabolism, multiple amino acid metabolism and other metabolic pathways, and they are closely related to each other. This study deepens the understanding of proteomic changes and structural/functional properties of rice proteins during steaming.

Rapid effectiveness of hydrolysed rice protein formulas on most digestive symptoms of infants.

Rapid effectiveness of hydrolysed rice protein formulas on most digestive symptoms of infants.

Characterization of rice endosperm-derived antidepressant-like peptide (REAP): An orally active novel tridecapeptide derived from rice protein

It is ideal to ingest bioactive substances from daily foods to stay healthy. Rice is the staple food for almost half of the human population. We found that an orally administered enzymatic digest of rice endosperm protein exhibits antidepressant-like effects in the tail suspension test (TST) using mice. A comprehensive peptide analysis of the digest using liquid chromatography-tandem mass spectrometry was performed, and a tridecapeptide QQFLPEGQSQSQK, detected in the digest, was chemosynthesized. Oral administration of the tridecapeptide exhibited antidepressant-like effects at a low dose comparable to classical antidepressant in the TST. This also exhibited anti-depressant-like effect in the forced swim test. We named it rice endosperm-derived antidepressant-like peptide (REAP). Intriguingly, intraperitoneal administration had no effect. Orally administered REAP(8−13) but not REAP(1−7) exhibited antidepressant-like activity, suggesting that the C-terminal structure is important for the antidepressant-like effect. We confirmed the presence of REAP, corresponding to rice glutelin type B4(130−142) and B5(130−142), in the digest. The effects of REAP were blocked by both dopamine D1 and D2 antagonists. These results suggest that it exerts its antidepressant-like activity through activation of the dopamine system.Taken together, oral administration of a novel tridecapeptide exhibited antidepressant-like effects via the dopamine system. This is the first report of a rice-derived peptide that exhibits antidepressant-like effects.

Biofortified Rice Provides Rich Sakuranetin in Endosperm

Sakuranetin plays a key role as a phytoalexin in plant resistance to biotic and abiotic stresses, and possesses diverse health-promoting benefits. However, mature rice seeds do not contain detectable levels of sakuranetin. In the present study, a transgenic rice plant was developed in which the promoter of an endosperm-specific glutelin gene OsGluD-1 drives the expression of a specific enzyme naringenin 7-O-methyltransferase (NOMT) for sakuranetin biosynthesis. The presence of naringenin, which serves as the biosynthetic precursor of sakuranetin made this modification feasible in theory. Liquid chromatography tandem mass spectrometry (LC–MS/MS) validated that the seeds of transgenic rice accumulated remarkable sakuranetin at the mature stage, and higher at the filling stage. In addition, the panicle blast resistance of transgenic rice was significantly higher than that of the wild type. Specially, the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) imaging was performed to detect the content and spatial distribution of sakuranetin and other nutritional metabolites in transgenic rice seeds. Notably, this genetic modification also did not change the nutritional and quality indicators such as soluble sugars, total amino acids, total flavonoids, amylose, total protein, and free amino acid content in rice. Meanwhile, the phenotypes of the transgenic plant during the whole growth and developmental periods and agricultural traits such as grain width, grain length, and 1000-grain weight exhibited no significant differences from the wild type. Collectively, the study provides a conceptual advance on cultivating sakuranetin-rich biofortified rice by metabolic engineering. This new breeding idea may not only enhance the disease resistance of cereal crop seeds but also improve the nutritional value of grains for human health benefits.

Enhanced viability and stability of the Lactobacillus reuteri DSM 17938 probiotic strain following microencapsulation in pea and rice protein-inulin conjugates

Probiotics, which offer various health benefits can face challenges in terms of stability during food processing, storage, and gastrointestinal digestion. Therefore, this study aimed to improve the stability and survival of probiotics during various processing conditions and storage. To address this issue, the study was designed to microencapsulate Lactobacillus reuteri DSM 17938 within plant proteins (specifically rice protein (RP) and pea protein (PeP)) and their Maillard reaction conjugated with inulin by spray-drying. The encapsulation efficiency (EE%), stability during storage and temperature, and the viability after simulated gastrointestinal digestion of the microcapsules were examined. The results demonstrate that individual proteins exhibited lower EE%; however, the Maillard conjugates showed increased EE%, with RC (rice protein conjugates) displaying a higher EE% (96.99%) than PC (pea protein conjugates) (92.87%) (p < 0.05). Fourier Transform Infrared Spectroscopy verified the interaction between different functional groups of the proteins and Maillard conjugated and indicated the successful encapsulation of Lactobacillus reuteri DSM 17938 cells. The results also suggested that RC-encapsulated probiotic cells exhibited maximum survival upon gastrointestinal transit, with a decline of only 1.24 and 1.52 log CFU/g after gastric and complete simulated gastrointestinal digestion, respectively. The viability of probiotics encapsulated with RC and PeC showed improvement compared to those encapsulated with RP and PeP, particularly during refrigerated and room temperature storage, thermal challenge, and simulated gastrointestinal transit. Overall, these findings suggest that plant proteins and prebiotic inulin conjugates could serve as promising new encapsulation matrices for the encapsulation of probiotics in food applications.

RETINOBLASTOMA RELATED 1 switches mitosis to meiosis in rice

The transition from mitosis to meiosis is a critical event in the reproductive development of all sexually reproducing species. However, the mechanisms that regulate this process in plants remain largely unknown. Here, we find that the rice (Oryza sativa L.) protein RETINOBLASTOMA RELATED 1 (RBR1) is essential to the transition from mitosis to meiosis. Loss of RBR1 function results in hyper-proliferative sporogenous-cell-like cells (SCLs) in the anther locules during early stages of reproductive development. These hyper-proliferative SCLs are unable to initiate meiosis, eventually stagnating and degrading at late developmental stages to form pollen-free anthers. These results suggest that RBR1 acts as a gatekeeper of entry into meiosis. Furthermore, cytokinin content is significantly increased in rbr1 mutants, whereas the expression of type-B response factors, particularly LEPTO1, is significantly reduced. Given the known close association of cytokinins with cell proliferation, these findings imply that hyper-proliferative germ cells in the anther locules may be attributed to elevated cytokinin concentrations and disruptions in the cytokinin pathway. Using a genetic strategy, the association between germ cell hyper-proliferation and disturbed cytokinin signaling in rbr1 has been confirmed. In summary, we reveal a unique role of RBR1 in the initiation of meiosis; our results clearly demonstrate that the RBR1 regulatory module is connected to the cytokinin signaling pathway and switches mitosis to meiosis in rice.

MoAti1 mediates mitophagy by facilitating recruitment of MoAtg8 to promote invasive growth in Magnaporthe oryzae.

Mitophagy is a selective autophagy for the degradation of damaged or excessive mitochondria to maintain intracellular homeostasis. In Magnaporthe oryzae, a filamentous ascomycetous fungus that causes rice blast, the most devastating disease of rice, mitophagy occurs in the invasive hyphae to promote infection. To date, only a few proteins are known to participate in mitophagy and the mechanisms of mitophagy are largely unknown in pathogenic fungi. Here, by a yeast two-hybrid screen with the core autophagy-related protein MoAtg8 as a bait, we obtained a MoAtg8 interactor MoAti1 (MoAtg8-interacting protein 1). Fluorescent observations and protease digestion analyses revealed that MoAti1 is primarily localized to the peripheral mitochondrialouter membrane and is responsible for recruiting MoAtg8 to mitochondria under mitophagy induction conditions. MoAti1 is specifically required for mitophagy, but not for macroautophagy and pexophagy. Infection assays suggested that MoAti1 is required for mitophagy in invasive hyphae during pathogenesis. Notably, no homologues of MoAti1 were found in rice and human protein databases, indicating that MoAti1 may be used as a potential target to control rice blast. By the host-induced gene silencing (HIGS) strategy, transgenic rice plants targeted to silencing MoATI1 showed enhanced resistance against M. oryzae with unchanged agronomic traits. Our results suggest that MoATI1 is required for mitophagy and pathogenicity in M. oryzae and can be used as a target for reducing rice blast.

Effect of tertiary processing on physical, optical, phytochemical as well as rheological properties of high-protein rice.

The first high-protein rice variety of India, CR Dhan 310, developed at ICAR-NRRI, Cuttack is being selected for the study. It contains 10.1% protein in milled rice as compared to 6-7% protein content in the milled rice of any other normal variety. It has intermediate amylose content (25.1%), medium bold grains rich in protein (10.1%) The significant changes in properties of raw and parboiled rice on processing were studied at statistical differences of p ≤ 0.05. These properties included physical, optical, antioxidant and rheological properties which changed with different processing techniques. All the three processes namely, puffing, popping and flaking increased the dimensions as compared to the raw rice. Peak viscosity measurements demonstrated the breakdown of starch molecules, with white rice having the greatest value (4145 cP) and popped rice having the lowest value (2017 cP) as a result of the starch granules being gelatinized during the production of popped rice. Highest anthocyanin content (2.93 mg/100 g) was observed in puffed rice, phenolic content (347.93 mg/100 g) was highest in popped rice and flaked/flattened rice showed highest flavonoid content (127.12 mg/100 g) indicating that tertiary processing of rice obtained higher values of phytochemicals when compared to the plain high-protein rice. This indicates that the processed products of rice can be consumed directly as ready-to-eat or can be used in preparation of other functional foods to combat malnutrition and build nutritional security. The study indicates that processing could improve the nutritional quality of the rice products.

Water binding ability changes of different proteins during high-moisture extrusion

High-moisture extrusion technology (40% ∼ 80% moisture content) has shown the advantages for producing plant-based meat products with rich meat-like fibrous structures; however, it faces the issue of insufficient juiciness. Juiciness is associated with water characteristics such as water holding capacity and water distribution, and the variations in water binding ability of proteins during high-moisture extrusion may offer valuable insights into this perspective. Thus, the water binding ability changes of plant proteins from five common sources during high-moisture extrusion were investigated in this study. Results showed the extrudates of soy protein isolate (SPI), soy protein concentrate (SPC) and wheat gluten (WG) exhibited fibrous structures at a centimeter level, respectively, and the microscopic morphology of SPI extrudates was more uniform. SPI showed the strongest water holding capacity and highest gel strength, leading to a faster binding rate with water compared to other proteins during the heating process. Moreover, the lowest water activity, freezable water content, T21 and T22 were found after extrusion of SPI, indicating that it was the most tightly bound to water. While, rice protein isolate (RPI) failed to extrude into a regular shape, and its extrudates showed the lowest density with a poor water binding ability. It was also found that the water activity of the extrudates was related to the solubility of the protein raw materials, and proteins with high solubility (PPP) showed lower water activity after extrusion. The results confirmed that the water binding ability of proteins could affect the water content, water state and distribution in the extrudates. These findings provided evidence for exploring the juiciness of plant-based meat products from the perspective of protein-water interaction.

Quantitative detection of crude protein in brown rice by near-infrared spectroscopy based on hybrid feature selection

It is important for rice breeding and quality evaluation to predict the protein content of brown rice rapidly and easily. In this study, near-infrared spectroscopy (NIRS) was utilized to establish a model for detecting crude protein content in brown rice based on 349 samples prepared from three kinds of brown rice, and the performance of the model was evaluated. Improved interval partial least squares (iPLS) was used to divide and screen different feature intervals after spectral preprocessing in this research. On this basis, competitive adaptive reweighted sampling (CARS) optimized the selected feature intervals, and finally 14 effective spectral features concentrated in 1160 nm–1338 nm were selected from 1050 features. The above hybrid feature selection has more advantages than the single selection. Support vector regression (SVR) calibration model was established, and partial least squares regression (PLSR) model commonly used in similar studies was selected as a comparison. The optimal spectral preprocessing method was selected according to the model prediction effect. The coefficient of determination (R2), R2 of cross-validation set (Rcv2), root mean square error of prediction (RMSEP), and relative percent difference (RPD) evaluated for the prediction model reached 0.9185, 0.8876, 0.2040% and 3.5194, respectively. The results showed that the designed method can be used for the rapid determination of the crude protein content of brown rice, providing a convenient, efficient and non-destructive method for related detection.

Growth pattern of paediatric patients affected by cow milk protein allergy fed with rice hydrolyzed formula.

Formulas made from hydrolyzed rice proteins (HRPF) are well-tolerated plant-based alternatives to cow's milk protein (CMP)-based formulas for the dietary management of paediatric patients with CMP allergy (CMPA). Growth in patients with CMPA fed with HRPF has been evaluated in several studies with conflicting results. The aim was to evaluate the growth pattern of children with CMPA over a 12-month follow-up period. Prospective cohort study evaluating growth patterns in challenge proven CMPA paediatric patients receiving HRPF for 12 months. Outcomes were anthropometry (body weight, body length, head circumference), adherence to the study formula and occurrence of adverse events (AEs). Sixty-six children were included and completed the 12-month study. At baseline, all CMPA patients were weaned. For the entire CMPA pediatric patients' cohort, from baseline to the end of the study period, the growth pattern resulted within the normal range of World Health Organization (WHO) growth references. The formula was well tolerated. Adherence was optimal and no AEs related to HRPF use were reported. HRPF is well tolerated and can help support healthy growth and development in infants and young children with CMPA. These type of formula can be given with complementary foods in the dietary management of CMPA.

High-yield BMP2 expression in rice cells via CRISPR and endogenous αAmy3 promoter

Plant cells serve as versatile platforms for the production of high-value recombinant proteins. This study explored the efficacy of utilizing an endogenous αAmy3 promoter for the expression of a bioactive pharmaceutical protein, specifically the mature region of human bone morphogenetic protein 2 (hBMP2m). Utilizing a refined CRISPR/Cas9-mediated intron-targeting insertion technique, which incorporates an artificial 3’ splicing site upstream of the target gene, we achieved a transformation efficiency of 13.5% in rice calli that carried the rice-codon optimized mature region of hBMP2 cDNA (rhBMP2m) in the αAmy3 intron 1. Both homozygous and heterozygous rhBMP2m knock-in rice suspension cell lines were generated. These lines demonstrated the endogenous αAmy3 promoter regulated rhBMP2m mRNA and rhBMP2m recombinant protein expression, with strongly upregulation in respond to sugar depletion. The homozygous rhBMP2m knock-in cell line yielded an impressive 21.5 μg/mL of rhBMP2m recombinant protein, accounting for 1.03% of the total soluble protein. The high-yield expression was stably maintained across two generations, indicating the genetic stability of rhBMP2m gene knock-in at the αAmy3 intron 1 locus. Additionally, the rice cell-derived rhBMP2m proteins were found to be glycosylated, capable of dimer formation, and bioactive. Our results indicate that the endogenous rice αAmy3 promoter–signal peptide-based expression system is an effective strategy for producing bioactive pharmaceutical proteins.Key points• The endogenous αAmy3 promoter-based expression system enhanced the yield of BMP2• The increased yield of BMP2 accounted for 1.03% of the total rice-soluble proteins• The rice-produced BMP2 showed glycosylation modifications, dimer formation, and bioactivity

Compositional aspect and mechanism of surface formation of spray-dried microparticles with surface-active rice protein hydrolysates

Flavourzyme enzymatically hydrolyzed rice protein isolate to different degrees of hydrolysis (DH, 2, 6, and 10%) to stabilize formulated linseed oil emulsions with different protein concentrations (0.5, 1.0, and 1.5%). The emulsions were spray dried, and the microstructure, surface composition by X-ray photoelectron spectroscopy (XPS), and oxidative stability of the resultant microparticles were investigated. The physicochemical properties of powders were also evaluated. DH and protein concentration did not affect solubility, hygroscopicity, wetting time, and particle size. However, a strong and positive correlation was found between DH and oxidative stability. The lowest peroxide value (2.48–1.99 meq/kg oil) was found from the powder formulated with protein hydrolysate (DH 10%) and 1.5% of protein concentration during the entire storage study. Fluorescence optical microscopy and atomic force microscopies also allowed identifying the effects of these variables on oxidative stability. Through XPS analysis, it was possible to observe that higher DH favored the surface accumulation of proteins at the powder surface. The protein content on the particle surface (9.8%) was overrepresented compared with the bulk composition (1.5%). These results showed that the degree of hydrolysis exerted an influence on the distribution of components and the percentage of protein on the powder surface.

Rice false smut virulence protein subverts host chitin perception and signaling at lemma and palea for floral infection.

The flower-infecting fungus Ustilaginoidea virens causes rice false smut, which is a severe emerging disease threatening rice (Oryza sativa) production worldwide. False smut not only reduces yield, but more importantly produces toxins on grains, posing a great threat to food safety. U. virens invades spikelets via the gap between the 2 bracts (lemma and palea) enclosing the floret and specifically infects the stamen and pistil. Molecular mechanisms for the U. virens-rice interaction are largely unknown. Here, we demonstrate that rice flowers predominantly employ chitin-triggered immunity against U. virens in the lemma and palea, rather than in the stamen and pistil. We identify a crucial U. virens virulence factor, named UvGH18.1, which carries glycoside hydrolase activity. Mechanistically, UvGH18.1 functions by binding to and hydrolyzing immune elicitor chitin and interacting with the chitin receptor CHITIN ELICITOR BINDING PROTEIN (OsCEBiP) and co-receptor CHITIN ELICITOR RECEPTOR KINASE1 (OsCERK1) to impair their chitin-induced dimerization, suppressing host immunity exerted at the lemma and palea for gaining access to the stamen and pistil. Conversely, pretreatment on spikelets with chitin induces a defense response in the lemma and palea, promoting resistance against U. virens. Collectively, our data uncover a mechanism for a U. virens virulence factor and the critical location of the host-pathogen interaction in flowers and provide a potential strategy to control rice false smut disease.

Study on the structure–activity relationship of rice immunopeptides based on molecular docking

Research on food-derived immunoregulatory peptides has attracted increasing attention of scientists worldwide. However, the structure–activity relationship of rice immunopeptides was not clearly. Herein, 114 rice immunopeptides were obtained by simulating the enzymatic hydrolysis of rice proteins and were further analyzed by NetMHCIipan-4.0. Subsequently, the molecular docking was used to simulate the binding of immunoreactive peptides to major histocompatibility complex class II (MHC-II) molecules. Results show that S, R, D, E, and T amino acid could easily form hydrogen bonds with MHC-II molecules, thus enhancing innate and adaptive immunity. Finally, glucose-modified rice immunopeptides were to investigate the binding of the peptides with MHC-II molecules after glycosylation modification; this provided a theoretical basis for the targeted modification of the generated immunopeptides. All in all, the present study provides a theoretical foundation to further utilize rice processing byproducts and other food products to enhance immunity.

Investigating the effects of grain quality, processing and environmental conditions on aflatoxin contamination in rice

This study examined the impact of aflatoxin contamination on rice, a widely consumed staple food. Various forms and types of rice from three regions in Pakistan between 2019 and 2022 were investigated for their relationship with processing, infestation severity and physicochemical characteristics. Semi-polished rice displayed the highest aflatoxin levels employing significant variability, while parboiled rice was also found to be contaminated. Nearly 22% of polished rice samples and 3% of brown rice samples exceeded the EU limit. Non-basmati rice varieties, particularly IRRI-6 (47.3 μg/kg), showed twice as much contamination as basmati rice. The coastal Zone-IV exhibiting significantly higher aflatoxin levels (avg. 14.40 µg/kg). Environmental conditions played a significant role, with moisture in brown rice and protein in parboiled rice exhibiting positive and negative correlations (p < 0.01) with aflatoxin levels, respectively. Principal Component Analysis (PCA) indicated that semi-finished and non-basmati rice were more associated with non-compliant rice. The first principal component, explaining 57.8% of variance, was positively loaded with aflatoxin, moisture, and insect infestation, while negatively loaded with protein, amylose, ash, immature, chalky, and foreign matter. These findings are insightful for local and international stakeholders for mitigating aflatoxin contamination in rice.

Glycemic Response in Nonhuman Primates Fed Gluten-Free Rice Cakes Enriched with Soy, Pea, or Rice Protein and Its Correlation with Nutrient Composition.

Celiac disease (CD) is a chronic disease caused by the consumption of gluten foods and is closely related to type 1 diabetes (T1D). Adherence to a gluten-free (GF) diet is the cornerstone of treating CD, and certain plant proteins added to GF foods affect blood glucose to varying degrees. The aim of this study was to analyze and compare the changes in glycemic index (GI) and incremental area under the postprandial glucose tolerance curve (IAUC) of various foods through consumption of GF foods supplemented with certain plant proteins in non-human primates. The test foods were GF rice cakes with 5%, 10%, and 15% added single plant proteins (rice protein, soy protein, and pea protein) mixed with rice flour, as well as 5%, 10%, and 15% gluten rice cakes, and rice flour alone, for a total of 13 food items, and 12 healthy cynomolgus monkeys were examined for their glucose levels in the blood after fasting and after eating each test food (50 g) for 15, 30, 45, 60, 90, and 120 min after fasting and eating each test food. Fingertip blood glucose levels were measured, and the nutrient content of each food, including protein, fat, starch, ash, and amino acids, was examined. All foods tested had a low GI (<50) when analyzed using one-way ANOVA and nonparametric tests. Postprandial IAUC was significantly lower (p < 0.05) for GF rice cakes with 15% pea protein (499.81 ± 34.46) compared to GF rice cakes with 5% pea protein (542.19 ± 38.78), 15% soy protein (572.94 ± 72.74), and 15% rice protein (530.50 ± 14.65), and GF rice cakes with 15% wheat bran protein (533.19 ± 34.89). A multiple regression analysis showed that glycine was negatively associated with IAUC in GF rice cakes with 5%, 10%, and 15% pea protein added (p = 0.0031 < 0.01). Fat was negatively correlated with IAUC in GF rice cakes supplemented with 5%, 10%, and 15% soy protein (p = 0.0024 < 0.01). In this study, GF rice cakes made with added pea protein were superior to other gluten and GF rice cakes and had a small effect on postprandial glucose.

Does protein deamidation enhance rice protein concentrate’s ability to produce and stabilize high internal phase emulsions?

Rice is one of the most consumed grains in the world. Rice protein has great nutritional value as a hypoallergenic protein and due to its high lysine content, a limiting amino acid in several other plant protein sources. However, rice protein has low solubility, hampering its use in many applications in the food industry. In this context, alkaline deamidation (0.5 h, 343 K, and pH 11) was applied to modify the protein structure of rice protein concentrate (RPC). After deamidation, two protein powders were produced: (i) one containing the whole protein fraction recovered after RPC deamidation (DT) and (ii) another containing only the soluble fraction recovered after RPC deamidation (DS). Protein dispersions were characterized by SDS-PAGE, zeta potential, solubility, surface hydrophobicity, and capacity to hold water and oil. RPC could not structure canola oil into a high internal phase emulsion (HIPE) due to its low solubility. DT and DS dispersions displayed solubility much higher than RPC and enabled the structuration of HIPEs with 75 % (w/w) canola oil and 25 % of DT or DS dispersions (2, 4, and 6 % w/w). HIPEs were characterized regarding particle size, microstructure, Turbiscan and oil loss stabilities, and rheological behavior for 60 days. Turbiscan analysis and oil loss measurements showed high stability, and the thixotropy tests showed high recovery in all HIPEs. Higher protein concentrations and DS dispersions produced HIPEs with smaller particle sizes. However, rheological measurements indicate that HIPEs produced with DT dispersions had better results, maintaining their structure over the 60 days. Furthermore, DT is cheaper to produce; therefore, DT 4 and 6 % w/w were the most promising for producing HIPEs. The HIPEs produced in this study displayed great potential as fat replacers.

Identification of the RRM1 gene family in rice (Oryza sativa) and its response to rice blast.

To better understand RNA-binding proteins in rice, a comprehensive investigation was conducted on the RRM1 gene family of rice. It encompassed genome-wide identification and exploration of its role in rice blast resistance. The physicochemical properties of the rice OsRRM1 gene family were analyzed. There genes were also analyzed for their conserved domains, motifs, location information, gene structure, phylogenetic trees, collinearity, and cis-acting elements. Furthermore, alterations in the expression patterns of selected OsRRM1 genes were assessed using quantitative real-time PCR (qRT-PCR). A total of 212 members of the OsRRM1 gene family were identified, which were dispersed across 12 chromosomes. These genes all exhibit multiple exons and introns, all of which encompass the conserved RRM1 domain and share analogous motifs. This observation suggests a high degree of conservation within the encoded sequence domain of these genes. Phylogenetic analysis revealed the existence of five subfamilies within the OsRRM1 gene family. Furthermore, investigation of the promoter region identified cis-regulatory elements that are involved in nucleic acid binding and interaction with multiple transcription factors. By employing GO and KEGG analyses, four RRM1 genes were tentatively identified as crucial contributors to plant immunity, while the RRM1 gene family was also found to have a significant involvement in the complex of alternative splicing. The qRT-PCR results revealed distinct temporal changes in the expression patterns of OsRRM1 genes following rice blast infection. Additionally, gene expression analysis indicates that the majority of OsRRM1 genes exhibited constitutive expressions. These findings enrich our understanding of the OsRRM1 gene family. They also provide a foundation for further research on immune mechanisms rice and the management of rice blast.

Plasma membrane-localized hexose transporter OsSWEET1b, affects sugar metabolism and leaf senescence.

OsSWEET1b is a hexose transporter protein, which localized in cell membranes and interacting with itself to form homodimer and knockout of OsSWEET1b resulted in reduced leaves sugar content and accelerating leaf senescence. In the rice genome, the SWEET gene family contains 21 homologous members, but the role of some of them in rice growth and development is still unknown. The function of the sugar transporter OsSWEET1b protein in rice was identified in this research. Expression analysis showed that the expression levels of OsSWEET1b in leaves were higher than that in other tissues. The hexose transport experiment confirmed that OsSWEET1b has glucose and galactose transporter activity in yeast. Subcellular localization indicates that OsSWEET1b protein was targeted to the plasma membrane and BiFC analysis showed that OsSWEET1b interacts with itself to form homodimers. Functional analysis demonstrated that the ossweet1b mutant plants were have reduced the sucrose, glucose, fructose, starch and galactose contents, and induced carbon starvation-related gene expression, which might lead to carbon starvation in leaves at filling stage. The ossweet1b knockout plants showed decreased chlorophyll content and antioxidant enzyme activity, and increased ROS accumulation in leaves, leading to leaf cell death and premature senescence phenotype at filling stage. In ossweet1b mutants, the leaf senescence-related gene expression levels were increased and the abundance of photosynthesis-related proteins was decreased. Loss of OsSWEET1b were affected the starch, sucrose metabolism and carbon fixation in photosynthetic organelles pathway by RNA-seq analysis. The destruction of OsSWEET1b function will cause sugar starvation, decreased photosynthesis and leaf senescence, which leading to reduced rice yield. Collectively, our results suggest that the OsSWEET1b plays a key role in rice leaves carbohydrate metabolism and leaf senescence.