Search Results (33)

Starch is the primary component of the endosperm and plays a crucial role in rice quality. Although the enzymes involved in starch synthesis have been extensively studied, the transcription factors that regulate these enzymes remain largely unknown. Here, we identified a MYB family transcription factor, OsMYBR1, that regulates starch biosynthesis in rice. OsMYBR1 is highly expressed during endosperm development. Mutations of OsMYBR1 result in reduced grain thickness and a decrease in 1000-grain weight. The endosperm of osmybr1 mutants exhibit rounded and loosely packed starch granules, decreased amylose content, altered fine structure of amylopectin, and modified physicochemical properties. The analysis of RT-qPCR showed that the expression of several starch-synthesis enzyme-coding genes (SSEGs), including OsGBSSⅠ, OsAGPL1, OsAGPL2, OsBEⅡb, OsISA1, PHOL, and OsSSⅢa, is altered in osmybr1 mutants. Further experiments indicated that OsMYBR1 directly binds to the promoters of OsGBSSⅠ, OsAGPL1, OsAGPL2, OsISA1, OsBEⅡb, and PHOL, resulting in an increase in the expression of OsGBSSⅠ but a decrease in the expression of OsAGPL2, OsISA1, and OsSSⅢa. In contrast, OsMYBR1-overexpressing endosperm appears normal, with starch granule morphology, increased amylopectin content, and improved alkali spreading value, indicating enhanced rice eating and cooking quality (ECQ). These findings suggest that the overexpression of OsMYBR1 could be a promising strategy for improving rice ECQ. Full article

Starch biosynthesis is crucial in determining rice quality during rice endosperm development. This study obtained a stable inheritable white-core endosperm mutant, h5, by treating the japonica rice variety Nipponbare with MNU (N-methyl-N-nitro-sourea). The mutated gene is an allele of OsAGPL2, which encodes the large subunit of ADP-glucose pyrophosphorylase (AGPase), a key and rate-limiting enzyme in the rice starch biosynthesis pathway. A G-C mutation in the third exon of OsAGPL2 led to impaired starch synthesis, significantly reduced amylose content (AC) and gel consistency (GC), and a marked decrease in AGPase activity. The haplotype analysis revealed that an SNP in the 3′UTR and two SNPs in the 5′UTR of OsAGPL2 were associated with significant differences in AC and GC among rice resources. These SNPs can be utilized to design molecular markers for breeding programs to improve rice quality. This study elucidates the impact of OsAGPL2 on the eating and cooking quality of rice. It identifies superior haplotypes, providing a theoretical foundation and molecular markers for accumulating minor-effect genes to enhance rice quality. Full article

Here, we investigated physiological responses, yield components, starch properties, and starch biosynthesis genes in five Thai rice (Oryza sativa L.) cultivars (SPR1, Hawm Daeng, RD43, RD69, and PTT1) with distinct starch characteristics under salt stress. Salt stress decreased flag leaf greenness (SPAD), normalized difference vegetation index (NDVI) levels, and carotenoid reflectance index 1 (CRI1) levels in all cultivars, resulting in reduced net photosynthesis, transpiration rates, and yield components across all cultivars, with Hawm Daeng and PTT1 being most susceptible. In contrast, RD69 and SPR1 were more tolerant, exhibiting recovered chlorophyll fluorescence levels and total performance index values after 3 days. Salt stress reduced apparent amylose content (AAC) and increased rapidly available glucose (RAG) levels in all cultivars. Granule-bound starch synthase I (GBSSI) expression declined the most in PTT1 and Hawm Daeng. SPAD, NDVI, CRI1, and photosynthetic parameters were correlated with GBSSI expression at the milky and dough stages of grain development. GBSSI expression levels showed little to no correlation with slowly available glucose but correlated with resistant starch levels at the booting stage of grain development. Salt stress affected yield components and rice starch quality, with variations depending on salt susceptibility, which in turn affected GBSSI expression levels during the milky and dough stages of grain development. Full article

The global significance of Colocasia esculenta, a tuber crop rich in nutritional value and starch, prompts further investigation into its corm development. Background: Previous studies have focused on starch accumulation within the tubers, yet the genetic and proteomic basis of corm expansion remains largely unexplored. This study aims to elucidate the key genes and proteins involved in this process. Methods: We selected ‘Lipu Taro No.1’ and conducted a longitudinal starch content analysis, full-length transcriptome sequencing, and a proteomic analysis during three distinct stages of corm development. Results: Our findings reveal a significant increase in both amylose and amylopectin contents as the corm develops, indicating the temporal regulation of starch biosynthesis. The integration of transcriptome and proteomic data identified differentially expressed genes and proteins associated with starch and sucrose metabolism, as well as plant hormone signal transduction. Conclusions: This study delineates a temporal gene expression pattern that is crucial for starch synthesis and provides insights into the regulatory mechanisms controlling corm expansion and starch deposition, offering valuable references for future molecular breeding strategies to enhance taro yield and quality. Full article

Tartary buckwheat is a nutrient-rich pseudo-cereal whose starch contents, including amylose and amylopectin contents, and their properties hold significant importance for enhancing yield and quality. The granule-bound starch synthase (GBSS) is a key enzyme responsible for the synthesis of amylose, directly determining the amylose content and amylose-to-amylopectin ratio in crops. Although one has already been cloned, the GBSS genes at the genome-wide level have not yet been fully assessed and thoroughly analyzed in Tartary buckwheat. This study comprehensively analyzed the FtGBSSs in Tartary buckwheat. Based on the genome data of Tartary buckwheat, five FtGBSS genes, namely FtGBSS-1 to FtGBSS-5, were identified on three chromosomes, exhibiting about 1800 bp lengths in their CDSs and numerous exons and introns in gene structures. Amino acid analyses revealed high homology in ten GBSS proteins from Tartary buckwheat, rice, maize, and Arabidopsis thaliana, with a specific starch synthase catalytic domain and ten conserved motifs. The Tartary buckwheat GBSS proteins had a closer relationship with GBSS proteins from monocot based on evolutionary relationship analysis. Expression analyses suggested that the FtGBSS genes showed distinct tissue-specific expression patterns in Tartary buckwheat and rice-Tartary buckwheat. Among them, FtGBSS-1, FtGBSS-2, and FtGBSS-4 were higher expressed in the root, stem, or flower, suggesting that they have a role in the amylose synthesis of these tissues. Notably, FtGBSS-3 and FtGBSS-5 were more highly expressed in seeds than in other tissues, suggesting that they have a pivotal role in amylose synthesis of the seeds of Tartary buckwheat. Furthermore, the cis acting elements in the promoters of FtGBSSs and their binding transcription factors (TFs) were investigated. A protein–protein interaction network was constructed and co-expression was analyzed based on the gene expression patterns of the FtGBSSs, and the identified TFs, belonging to bZIP, ERF, bHLH, and MADS-box TF families, were identified within this network, and their expression patterns were significantly correlated to the expression patterns of two seed-specific FtGBSS genes (FtGBSS-3 and FtGBSS-5). Finally, FtGBSS1-5 was successfully transformed into rice through transgenic manipulation, and the FtGBSS1-5 overexpression lines showed an increase in amylose content accompanied by a reduction in amylopectin and total starch contents compared with WT. Overall, this research not only deepens our understanding of the molecular mechanisms of amylose synthesis in Tartary buckwheat, but also provides scientific insights for enhancing crop amylose content and quality through molecular breeding. Full article

Abscisic acid (ABA) plays an important regulatory role in the grain filling process, which in turn will affect the final yield and quality of rice. The ABA biosynthesis genes of OsNCED3 and degradation gene OsABA8ox3 affect the ABA content, and then further regulate the ABA signaling. During the development of rice panicle, compared with primary grains (superior grains) growing on primary branches, secondary grains (inferior grains) growing on secondary branches exhibit characteristics. However, little is reported on the physicochemical characteristics of starch between superior and inferior grains in ABA related transgenic lines. In this study, OsNCED3 and OsABA8ox3 transgenic plants were used as materials. The results showed that compared with the WT, the OsNCED3-RNAi lines on grain weight was consistent with the trend of superior and inferior grains, while the OsABA8ox3-RNAi lines affected superior or inferior grains. The total starch and soluble sugar content of grains decreased in both OsNCED3-RNAi and OsABA8ox3-RNAi lines, and the total starch content of superior and inferior grains in OsABA8ox3-RNAi lines decreased. The starch granule size distribution of all samples showed a bimodal and increased proportion of starch grains with large granule size, in which the influence on inferior grains was greater than that of superior grains, which eventually led to a significant increase in their average granule size. The apparent amylose content of inferior grains increased significantly in most lines. The swelling power of the superior grains decreased significantly, while that of the inferior grains increased significantly. Fourier analysis showed that the order degree of starch granule surface decreased in the superior grains of the RNAi line, while it increased in the inferior grains of the OsABA8ox3-RNAi line but decreased in the OsNCED3-RNAi lines. In the superior grains, the relative crystallinity of starch decreased in the OsNCED3-RNAi lines, but remained unchanged or increased in the OsABA8ox3-RNAi line. In inferior grains, the relative crystallinity of starch decreased in the ABA synthesis RNAi line, but increased in the OsABA8ox3-RNAi line. In summary, the influence of ABA on the physicochemical properties of inferior grains is greater than that of superior grains. Full article

Heat treatment is a widely used physical technology for postharvest fruit and crops. The Chinese chestnut cultivar “Kuili” has high sugar and amylose contents, and is popular among people. However, the chestnut quality decreases quickly after harvest. In order to maintain the chestnuts’ quality during storage, this study explores five hot water treatments for chestnuts: T1 (control, no treatment), T2 (50 °C), T3 (65 °C), T4 (75 °C), and T5 (90 °C) for 45 min. T1 was dried at ambient temperature, while the other heat treatments were dried at 30 °C for 30 min. After treatment, chestnuts were placed in plastic trays, covered with a 15 μm thick PVC film, and stored at 4 °C with 70% relative humidity; they remained in the same air for 120 days. Results indicated that T3 and T4 showed slight color changes while maintaining shell and kernel firmness, and their weight loss was reduced (+5–8%), as well as their decay rate (limited to within 20%). The T3, T4, and T5 treatments (from days 60 to 120) decreased their pest survival rates to <2%. Additionally, heat treatments facilitated the accumulation of total soluble sugar and increased the expression of sugar biosynthesis-related genes. Meanwhile, T3 and T4 delayed starch reduction (they maintained relatively higher contents, from 288 to ~320 mg g⁻¹ DW) and altered some starch biosynthesis genes. Furthermore, T2, T3, and T4 exhibited higher antioxidant activity and lower hydrogen peroxide (H₂O₂) and superoxide anions (O₂⁻) contents than T1. At the end of storage, the scores of T3 and T4 treatments were 55.1 and 52.3, and they ranked first and second among the five treatments, respectively. Therefore, these findings provide valuable insights for controlling postharvest losses in chestnuts. Full article

Rice (Oryza sativa) is a cereal crop with a starchy endosperm. Starch is composed of amylose and amylopectin. Amylose content (AC) is the principal determinant of rice quality, but varieties with similar ACs can still vary substantially in their quality. In this study, we analyzed the total AC (TAC) and its constituent fractions, the hot water-soluble amylose content (SAC) and hot water-insoluble amylose content (IAC), in two sets of related chromosome segment substitution lines of rice with a common genetic background grown in two years. We searched for quantitative trait loci (QTLs) associated with SAC, IAC, and TAC and identified one common QTL (qSAC–6, qIAC–6, and qTAC–6) on chromosome 6. Map-based cloning revealed that the gene underlying the trait associated with this common QTL is Waxy (Wx). An analysis of the colors of soluble and insoluble starch–iodine complexes and their λ_max values (wavelengths at the positions of their peak absorbance values) as well as gel permeation chromatography revealed that Wx is responsible for the biosynthesis of amylose, comprising a large proportion of the soluble fractions of the SAC. Wx is also involved in the biosynthesis of long chains of amylopectin, comprising the hot water-insoluble fractions of the IAC. These findings highlight the pleiotropic effects of Wx on the SAC and IAC. This pleiotropy indicates that these traits have a positive genetic correlation. Therefore, further studies of rice quality should use rice varieties with the same Wx genotype to eliminate the pleiotropic effects of this gene, allowing the independent relationship between the SAC or IAC and rice quality to be elucidated through a multiple correlation analysis. These findings are applicable to other valuable cereal crops as well. Full article

Barley with high grain β-glucan content is valuable for functional foods. The identification of loci for high β-glucan content is, thus, of great importance for barley breeding. Segregation mapping for the content in β-glucan and other barley grain components (starch, protein, lipid, ash, phosphorous, calcium, sodium) was performed using the progeny of the cross between Glacier AC38, a mutant with high amylose, and CDC Fibar, a high β-glucan waxy cultivar. The offspring of this cross showed transgressive segregation for β-glucan content. Linkage analysis based on single-nucleotide polymorphism (SNP) molecular markers was used for the genotyping of the parents and recombinant inbred lines (RILs). Two Quantitative Trait Loci (QTL) for β-glucan content and several QTL for other grain components were found. The former ones, located on chromosomes 1H and 7H, explained 27.9% and 27.4% of the phenotypic variance, respectively. Glacier AC38 provided the allele for high β-glucan content at the QTL on chromosome 1H, whereas CDC Fibar contributed the allele at the QTL on chromosome 7H. Their recombination resulted in a novel haplotype with higher β-glucan content, up to 18.4%. Candidate genes are proposed for these two QTL: HvCslF9, involved in β-glucan biosynthesis, for the QTL on chromosome 1H; Horvu_PLANET_7H01G069300, a gene encoding an ATP-Binding Cassette (ABC) transporter, for the QTL on chromosome 7H. Full article

In recent years, the semi-glutinous japonica rice variety has been extensively utilized in Jiangsu Province to greatly increase rice quality. Nevertheless, the increasing occurrence of seed variation presented a major threat to rice quality. Enhancing the quality of rice grains has emerged as a critical factor in guaranteeing consumer acceptance. Throughout this investigation, five lines (VJ1, VJ2, VJ3, VJ4, and VJ5) selected from the Nanjing9108 population in Liyang were used as research materials, and original cultivars of Nanjing9108 (CKJ1) provided by the original breeder were utilized as control materials to compare rice quality and differential metabolites. VJ4 and VJ3 demonstrated a significant reduction in milled rice rate and head milled rice rate when contrasted to CKJ1. Compared with CKJ1, the amylose content of the five strains was significantly increased. Only VJ3 amplified the 106 bp target band, and its 2-AP content was 0 ng/g. Most metabolites are mainly enriched in cutin, suberine, wax biosynthesis, histidine, and tryptophan metabolism. The primary metabolites throughout the metabolic pathway involve lipids and lipid-like molecules (mono palmitin, alpha-eleostearic, and palmitic acid) and amino acid metabolites (L-glutamate, L-tryptophan, and L-serine). The identification of these key metabolites helps in the discovery of prospective biomarkers for screening seed variation throughout seed production. Full article

The aim of this review was to provide an updated outlook on the relevance of momilactones in rice during the 50 years since their discovery. Momilactones A (MA) and B (MB) were initially extracted from rice husks in 1973 and have since been identified in various parts of the rice plant including leaves, bran, straw, roots, and root exudates. The biosynthesis of these compounds in rice initiates from geranylgeranyl diphosphate (GGDP) and progresses through several cyclization stages. The genes governing the synthesis of MA and MB are located on chromosome 4 within the rice genome. Concentrations of these compounds vary across different parts of the rice plant, ranging from 2 to 157 μg/g. Notably, Japonica rice varieties tend to have higher levels of MA and MB (157 and 83 μg/g, respectively) compared to Indica varieties (20.7 and 4.9 μg/g, respectively). There is a direct correlation between the levels of MA and MB and the increase in antioxidant activity, protein, and amylose content in rice grains. The production of these compounds is enhanced under environmental stresses such as drought, salinity, chilling, and UV exposure, indicating their potential role in rice’s tolerance to these conditions. MA and MB also demonstrate allelopathic, antibacterial, and antifungal properties, potentially improving the resilience of rice plants against biotic stressors. Although their antioxidant activity is modest, they effectively inhibit leukemia cells at a concentration of 5 µM. They also show promise in diabetes management by inhibiting enzymes like α-amylase (with IC₅₀ values of 132.56 and 129.02 mg/mL, respectively) and α-glucosidase (with IC₅₀ values of 991.95 and 612.03 mg/mL, respectively). The therapeutic qualities of MA and MB suggest that cultivating rice varieties with higher concentrations of these compounds, along with developing their derivatives, could benefit the pharmaceutical industry and enhance treatments for chronic diseases. Consequently, breeding rice cultivars with increased momilactone levels could offer substantial advantages to rice farmers. Full article

The application of nanotechnology in agricultural neighborhoods is rapidly developing with the aim of promoting growth and enhancing crop tolerance to environmental stresses. However, there are fewer reports on the application of graphene nanoparticles in practical production, especially in fragrant rice. In early-season and late-season pot experiments conducted in 2022, the effects of graphene on the yield, grain quality, 2-acetyl-1-pyrroline (2-AP) and antioxidant systems of two fragrant rice cultivars (19× and Meixiangzhan) were examined at concentrations of 9 g/hm², 18 g/hm² and 27 g/hm². The results showed that graphene T1 treatment at 9 g/hm² significantly increased the activity of PDH and P5CS, promoted the synthesis of proline and P5C and significantly increased the 2-AP content of the grains of the two fragrant rice cultivars by 10.33–39.88% and 22.05–65.76%, respectively, in both growing seasons. Meanwhile, the lower concentration of T1 treatment (9 g/hm²) increased the grains per panicle and 1000-grain weight, enhancing the grain yield of both fragrant rice cultivars. The T1 treatment (9 g/hm²) had significant effects on the appearance and nutritional quality of both fragrant rice cultivars. It increased the head rice rate and protein content of the grains while also increasing the amylose content of 19× and reducing the chalkiness degree of 19×. Conversely, the T1 treatment reduced the amylose content and increased the chalkiness degree of Meixiangzhan. In addition, the low concentration of T1 treatment significantly increased the POD and SOD activities, increased the content of photosynthetic pigments and decreased the content of MDA in the leaves. However, 18 g/hm² and 27 g/hm² had slightly negative effects on yield, grain quality and fragrance biosynthesis in both fragrant rice cultivars. Furthermore, the results of structural equation modeling showed that antioxidant enzymes had a significant, positive effect on the grain’s 2-AP content and 2-AP synthesis-related enzyme activity, and photosynthetic pigments had a significant, positive effect on yield and grain appearance quality, while rice appearance quality and nutritional quality had significant, positive effects on yield. Overall, this study showed that suitable concentrations of graphene have good potential for use in fragrant rice production, but additional attention should be paid to the concentration of graphene application. Full article

To understand the relationship between the genotype of maize plants and differences in their origin and the ploidy of the genome, which carry gene alleles programming the biosynthesis of various starch modifications, the thermodynamic and morphological features of starches from the grains of these plants have been studied. This study investigated the peculiarities of starch extracted from subspecies of maize (the dry matter mass (DM) fraction, starch content in grain DM, ash content in grain DM, and amylose content in starch) belonging to different genotypes within the framework of the program for the investigation of polymorphism of the world collection of plant genetic resources VIR. Among the starch genotypes of maize studied, four groups comprised the waxy (wx), conditionally high amylose (“ae”), sugar (su), and wild (WT) genotypes. Starches with an amylose content of over 30% conditionally belonged to the “ae” genotype. The starches of the su genotype had fewer starch granules than other investigated genotypes. An increase in amylose content in the investigated starches, accompanied by a decrease in their thermodynamic melting parameters, induced the accumulation of defective structures in the starches under study. The thermodynamic parameters evaluated for dissociation of the amylose–lipid complex were temperature (T_aml) and enthalpy (H_aml); for the su genotype, temperature and enthalpy values of dissociation of the amylose–lipid complex were higher than in the starches from the “ae” and WT genotypes. This study has shown that the amylose content in starch and the individual features of the maize genotype determine the thermodynamic melting parameters of the starches under study. Full article

Starch branching enzyme IIb (BEIIb) and soluble starch synthase IIa (SSIIa) play important roles in starch biosynthesis in cereals. Deficiency in the BEIIb gene produces the amylose extender (ae) mutant rice strain with increased amylose content (AC) and changes in the amylopectin structure. The SSIIa gene is responsible for the genetic control of gelatinization temperature (GT). The combined effects of BEIIb and SSIIa alleles on the AC, fine structures, and physicochemical properties of starches from 12 rice accessions including 10 recombinant inbred lines (RIL) and their two parents were examined in this study. Under the active BEIIb background, starches with the SSIIa-GC allele showed a higher GT than those with the SSIIa-TT allele, resulting from a lower proportion of A chain and a larger proportion of B1 chains in the amylopectin of SSIIa-GC. However, starch with the BEIIb mutant allele (be2b) in combination with any SSIIa genotype displayed more amylose long chains, higher amylose content, B2 and B3 chains, and molecular order, but smaller relative crystallinity and proportion of amylopectin A and B1 chains than those with BEIIb, leading to a higher GT and lower paste viscosities. These results suggest that BEIIb is more important in determining the structural and physicochemical properties than SSIIa. These results provide additional insights into the structure-function relationship in indica rice rather than that in japonica rice and are useful for breeding rice with high amylose content and high resistant starch. Full article

Starch is a major component of crop grains, and its content affects food quality and taste. Tartary buckwheat is a traditional pseudo-cereal used in food as well as medicine. Starch content, granule morphology, and physicochemical properties have been extensively studied in Tartary buckwheat. However, the complex regulatory network related to its starch biosynthesis needs to be elucidated. Here, we performed RNA-seq analyses using seven Tartary buckwheat varieties differing in starch content and combined the RNA-seq data with starch content by weighted correlation network analysis (WGCNA). As a result, 10,873 differentially expressed genes (DEGs) were identified and were functionally clustered to six hierarchical clusters. Fifteen starch biosynthesis genes had higher expression level in seeds. Four trait-specific modules and 3131 hub genes were identified by WGCNA, with the lightcyan and brown modules positively correlated with starch-related traits. Furthermore, two potential gene regulatory networks were proposed, including the co-expression of FtNAC70, FtPUL, and FtGBSS1-3 in the lightcyan module and FtbHLH5, C3H, FtBE2, FtISA3, FtSS3-5, and FtSS1 in the brown. All the above genes were preferentially expressed in seeds, further suggesting their role in seed starch biosynthesis. These results provide crucial guidance for further research on starch biosynthesis and its regulatory network in Tartary buckwheat. Full article