Rice (Oryza sativa L.) is one of the most widely cultivated cereal crops in the world and plays a vital role in global food security. Aging is a natural phenomenon that occurs during the storage of rice grains and the mechanisms are still not completely understood. During the storage of rice, the physicochemical properties of sensory, cooking and gelatinization, and starch structure and function change to different degrees. These changes are closely related to storage time and temperature and have irreversible impacts on rice quality. While the changes in physicochemical properties caused by rice aging have been intensively investigated, few studies have focused on changes in starch fine structure following storage. This review examined the types and methods of artificial aging as well as their extensive effects on physicochemical properties and changes in starch fine structure, which provides a theoretical basis for further elucidation of rice aging mechanisms.

Lipids, as essential nutrients in rice seeds, are of significant importance. Enhancing the oil content in rice seeds and optimizing its beneficial fatty acids and antioxidant substances are current trends in rice quality breeding. In this study, we reviewed the principal constituents and functions of rice oil, oil synthesis and regulatory pathways, regulatory genes and networks of rice oil, and genetic improvement of rice oil. The aims are to deepen the understanding of rice oil biosynthesis and provide new insights and directions for creating high-oil and high-quality rice germplasm resources in the future.

Anthocyanidins and proanthocyanidins have important health benefits for the human body. Anthocyanidins are present mainly as glycosylated or acetylated anthocyanins in nature, and proanthocyanidins exist in the form of polymers, with a wide variety of types and antioxidant properties. Pigmented rice, especially black rice, contains abundant anthocyanidins and proanthocyanidins, and it is becoming favorable. Here, we reviewed the research progress on anthocyanidins and proanthocyanidins in rice, emphasizing their molecular genetic mechanisms, isolation, purification, and detection methods, as well as their effects on starch physicochemical and digestive properties. Furthermore, we proposed several perspectives for future studies on pigmented rice, providing alternative considerations for further development, utilization and breeding of pigmented rice.

γ-aminobutyric acid (GABA), as a four-carbon and non-protein amino acid, is one of the important bioactive components in germinated brown rice. In this paper, the recent researches on GABA in germinated brown rice were summarized. It was found that GABA was mainly located in the rice germ, and the GABA content exhibited significant genetic diversity. The GABA content of indica rice was generally higher than that of japonica rice. Soaking conditions such as soaking temperature, soaking time and soaking method significantly affected GABA production in germinated brown rice. Meanwhile, the accumulation rate and amount of GABA were closely related to germination conditions such as germination temperature, germination time and germination method. In addition, abiotic stress treatments such as adversity stress, ultrasonic treatment and pulsed light irradiation could effectively promote GABA accumulation in germinated brown rice. The GABA branch and polyamine degradation pathway are the main biosynthesis and metabolic pathways of GABA in germinated brown rice, which are regulated by several key enzymes, such as glutamic acid decarboxylase, GABA transaminase and succinic semialdehyde dehydrogenase. The potential biological functions of GABA in germinated brown rice and the development and application of functional foods such as germinated brown rice staple foods and beverages rich in GABA were discussed, and the future work on GABA in germinated brown rice was also prospected. This paper provides a theoretical reference for the breeding of GABA-enriched rice and the development of nutritional foods of GABA-enriched germinated brown rice.

Amylose is widely regarded as an important factor affecting the eating quality and appearance quality of rice. It is mainly synthesized by granule-bound starch synthase Ⅰ (GBSSⅠ) encoded by the Waxy (Wx) gene. In this study, the glutinous mutant r162 was obtained from an ethyl methanesulfonate (EMS)-treated population of japonica rice cv. Ningjing 2. Compared with wild type (WT), the grains of this mutant showed a significant decrease in length, width and 1 000-grain mass, presenting a dull, opaque appearance reminiscent of clouds or fog. Scanning electron microscopy analysis of starch morphology revealed that there were some pores in the starch granules of mutant r162. The iodine staining of semi-thin sections indicated that the amyloplast arrangement in the developing endosperm of mutant r162 was similar to that in the WT, but the staining color was lighter. Physicochemical property analysis revealed that the total starch, total protein and total lipid contents of mutant r162 and WT were not significantly different. However, the apparent amylose content significantly decreased, and the gel consistency increased in mutant r162. Besides, the pasting property was also significantly altered, and the breakdown, setback, consistency, and the swelling volume of rice flour in urea of mutant r162 were lower than WT. Through the gene mapping and sequencing, the mutant gene Wx was localized on the short arm of chromosome 6. The first base of the seventh intron 7 (Int7-1) of the Wx gene in the mutant r162 was replaced from guanine (G) to adenine (A), resulting in a deletion of 10 bases in the Wx coding sequence and causing a mistranslation from the 256th amino acid, leading to premature termination of protein translation. Therefore, it was named Wx^－r162 . Further Western blot analysis revealed a marked decrease in GBSSⅠ protein levels in mutant r162, and enzyme activity assay also showed that the activity of GBSSⅠ in the mutant r162 was significantly lower than that in WT. In summary, the Wx^－r162 gene is a novel allelic variant whose mutation causes a decrease in GBSSⅠ activity, resulting in reduced apparent amylose content and an opaque phenotype in grains.

The metabolism of rice endosperm depends on the precise regulation of several post-translational modification (PTM)-based signaling networks, including phosphorylation and ubiquitination modifications. This study, integrating analysis of proteins from phosphoproteome and ubiquitinated proteome, identified 143 proteins with both phosphorylated and ubiquitinated sites, providing a basis for understanding the crosstalk mechanism between phosphorylation and ubiquitination modifications in rice endosperm. On the one hand, phosphorylation modification of key proteins involved in the ubiquitin-proteasome system contributed to the regulation of ubiquitination modification; on the other hand, ubiquitination modification of protein kinases and phosphatases might affect the phosphorylated signaling network. Under high temperature stress, phosphorylation and ubiquitination modifications jointly regulated the synthesis pathway of phenolic compounds, ultimately affecting the ability of phenolic compounds to scavenge reactive oxygen species and plant resistance to stress. Several enzymes related to starch metabolism possessed both phosphorylation and ubiquitination modifications, and 18 pairs of sites with different modification types appeared adjacent to the same protein, revealing the crosstalk mechanism between different modifications and the synergistic regulation of starch metabolism by phosphorylation and ubiquitination modifications under high temperature stress.

The application of near-infrared spectroscopy has gained significant traction for crop sample component detection and rapid screening of breeding materials in recent years, while limited studies have been conducted on the high-throughput detection of the major carbon and nitrogen metabolic components in rice source-sink organs, particularly in rice internode samples. In this study, 576 representative internode samples obtained from the experiment were used as materials. On the basis of the chemical measured values of the samples, the near-infrared spectral information of the samples was collected, and the models of the major carbon and nitrogen metabolic components of the rice internodes, such as sucrose, starch and total nitrogen, were constructed via partial least square (PLS). The model validation results showed that the coefficients of determination of the sucrose, starch and total nitrogen contents of the validation sets in the PLS model of the rice internodes were 0.988, 0.977 and 0.957, respectively. The relative percent deviations were all greater than three, and the performance indexes were 85.20, 85.80 and 86.50, respectively, indicating that the predicted results of the established models were accurate and reliable. In addition, the PLS models of starch and nitrogen contents and C/N ratio of rice leaves and sheaths also exhibited high accuracy. In this study, the near-infrared spectroscopy model of the major carbon and nitrogen metabolic components of rice internodes was constructed, which provided technical support for the study of rice cultivation physiology and high-yield cultivation theory.

Rice should be harvested in the best harvest period, either too early or too late, as this can affect quality. In this study, Nanjing 3908 was used to investigate the differences in basic component contents, gelatinization characteristics, thermodynamic characteristics, molecular weight, short-range order and crystal structure of japonica rice harvested in different periods in Nanjing (Jiangsu, China) and Changzhou (Jiangsu, China). The effects of harvest period on rice quality were analyzed. The results showed that the quality of Nanjing 3908 was affected by different planting sites and harvest periods. With delayed harvest, the 1 000-grain mass of samples harvested in the second phase in Nanjing (N-3908-2) was significantly greater than that in the third phase (N-3908-3), while the 1 000-grain mass of samples collected in Changzhou (C-3908-1 to C-3908-3) exhibited no significant changes. The eating qualities of N-3908-2 and C-3908-3 were the best. Compared with N-3908-1, N-3908-2 had a greater protein content, lower hardness, and lower setback of starch after gelatinization. Compared with C-3908-2, C-3908-3 had a greater protein content, unchanged hardness, and enhanced gelatinization ability. In general, with delayed harvest, the gelatinization ability of starch improved, and the eating quality was better, indicating that Nanjing 3908 had an optimal harvest period. Therefore, if eating quality is the main criterion for determining the harvest period, Nanjing 3908 should not be harvested earlier than 65 d after heading. In summary, the optimum harvest period of the same variety was different among the different planting sites. This result provides a theoretical basis for further research on the optimum harvest period of japonica rice.

In order to fully understand the spatio-temporal distribution and development status of indica rice quality in China, a total of 70 146 indica rice grain samples were collected from 12 provincial-level administrative regions, including Anhui, Chongqing, Fujian, Guangdong, Guangxi, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, and Zhejiang from 2002 to 2022. The grain length, head rice percentage, chalkiness degree, translucency, apparent amylose content, alkali spreading value, gel consistency and protein content were tested. The development trend of indica rice quality in China was analyzed by principal component analysis. The results showed that the indica rice grain samples from Henan and Jiangsu had shorter grain lengths and higher head rice percentages, and those from Guangdong and Jiangsu had lower chalkiness degrees and higher proportions of translucency with grade 1. The apparent amylose contents of the indica rice grain samples from Zhejiang, Jiangxi and Hunan were higher and the differences among the varieties were larger. The alkali spreading values of the indica rice grain samples from Jiangsu, Chongqing and Guangdong were higher. In the past 10 years, the grain length, alkali spreading value of indica rice increased annually, and the chalkiness degree, translucency, apparent amylose content and protein content decreased gradually, and the differences among the varieties became smaller. Overall, the quality of the indica rice varieties in China has obviously improved, which is developing towards the tendency of long grain, good appearance and good taste in the recent 21 years.

Taking indica rice as the research object, solid phase micro-extraction (SPME) and solvent-assisted flavor evaporation (SAFE) coupled with gas chromatography-olfactory-mass spectrometry (GC-O-MS) were applied to identify and characterize the aroma compounds in cooked rice. The key aroma components of cooked rice were further identified through quantitative analysis, odor activity value (OAV), and aroma recombination and omission experiments. The results showed that a total of 49 aroma compounds were identified, among which 2-methylbutanal, hexanal, 2-pentylfuran, nonanal, 1-octen-3-ol, (E)-2-nonenal, (E)-2-decenal, acetoin, 2(5H)-furanone, and 2-acetyl-1-pyrroline were screened out as the key aroma compounds. Seven sensory characteristics of cooked rice were evaluated using sensory quantitative descriptive analysis, namely cooked grain, nutty, grassy, caramel, sweet, fruity, and floral aromas. Partial least squares regression (PLSR) analysis showed that 2-methylbutanal, 2-pentylfuran, and 2(5H)-furanone were related to the formation of nutty and sweet sensory attributes; hexanal, (E)-2-nonenal, (E)-2-decenal, 2-methoxy-4-vinylphenol and indole were related to grassy and floral aromas; nonanal and decanal were related to fruity aroma; and 2-acetyl-1-pyrroline was significantly correlated with caramel aroma. Cooked grain aroma, an important sensory attribute of cooked rice, had a significantly positive correlation with various aroma compounds. This study provides a scientific basis for the regulation of cooked rice flavor and the construction of a sensory quality evaluation system.

The edible qualities, gelatinization properties and in vitro digestive properties of brown rice, white rice, parboiled brown rice and parboiled white rice were studied. The results showed that the whiteness of parboiled brown rice and parboiled white rice was lower than that of brown rice and white rice, respectively. The taste value (including the taste value of cooked rice and the taste value of raw rice) of parboiled brown rice and parboiled white rice was lower than that of brown rice and white rice, respectively. The taste value of cooked rice of parboiled white rice was 70.95±3.72, which was significantly higher than that of parboiled brown rice (36.13±1.53, P＜0.05). The gelatinization enthalpy of parboiled brown rice and parboiled white rice [(1.39±0.08) J/g and (1.32±0.04) J/g, respectively] was significantly lower than that of brown rice and white rice [(5.62±0.99) J/g and (8.32±0.17) J/g, respectively]. The in vitro digestibilities of parboiled brown rice and parboiled white rice at 240 minutes were (57.01±0.78)% and (60.23±0.35)%, respectively, while the in vitro digestibilities of brown rice and white rice at 240 minutes were (61.90±0.64)% and (66.10±0.16)%, respectively. The whiteness, taste value of cooked rice and gelatinization enthalpy of parboiled brown rice after parboiling treatment were significantly reduced compared with those of brown rice. In addition, the in vitro digestibility, rapidly digestible starch (RDS) content and glycemic index (GI) of parboiled brown rice were decreased, while the slowly digestible starch (SDS) and resistant starch (RS) contents of parboiled brown rice were increased compared with those of brown rice. The whiteness, taste value of cooked rice and gelatinization enthalpy of parboiled white rice after parboiling treatment were significantly reduced compared with those of white rice. The in vitro digestibility, RDS content and GI of parboiled rice were reduced, while the SDS and RS contents of parboiled white rice were increased compared with those of white rice. This study may provide a basis for the research and development of nutritious and healthy rice products.

Phosphorus (P) is one of the essential macronutrients for plant growth and development. Plants absorb phosphorus from the soil mainly in the form of inorganic phosphate (Pi). However, Pi in the soil is easily fixed, and its availability is low. Therefore, it is of great significance to study the molecular mechanisms of Pi starvation response (PSR) for improving the effective utilization of P in crops. In the past 20 years, great progress has been made in the study of the regulatory mechanisms of plant responses to Pi deficiency. Here, we systematically reviewed the research progress achieved in recent years both domestically and internationally, including local PSR signaling-mediated alteration of root morphogenesis, the PHR (PHOSPHATE STARVATION RESPONSE)-SPX (SYG1/Pho81/XPR1)-centered systemic PSR signaling network, the molecular mechanism of the symbiosis of rice arbuscular mycorrhizal fungi under Pi stress conditions, the transportation and allocation of Pi from rhizospheres to shoots, and the relocation and reuse of Pi from leaves to seeds. Finally, we discussed the future research priorities on the molecular mechanisms of PSR. This review summarizes current results and looks forward to future research directions to facilitate the study of PSR in plants and the improvements of Pi utilization efficiency in crops.

Over a long period of evolution, plant pathogenic fungi have developed a wide range of intricate and sophisticated strategies to invade their host plants, and the precise regulation of gene expression is necessary for interactions between plants and these pathogens. Epigenetic regulation refers to the process of altering DNA and proteins on chromosomes through chemical modifications, thereby regulating gene expression. These epigenetic regulations include DNA methylation, histone methylation, histone acetylation, and chromatin remodeling. Increasing evidence suggests that epigenetic regulation plays a crucial role in transcriptional reprogramming of plant pathogenic fungal genes, which affects their development, environmental stress response, biosynthesis of secondary metabolites and pathogenicity. This paper reviewed the recent advancements in epigenetic regulators, including histone modification and chromatin remodeling, and their roles in the development and pathogenicity of plant pathogenic fungi and offered insights into the current research prospects to lay a solid theoretical foundation for future disease control research.

An increasing number of studies have shown that the intestinal flora and microbial ecology mediated by the intestinal flora play key roles in metabolic disorders associated with high-fat and high-fructose diet. In this study, we investigated the effects of Xihu Longjing tea on the intestinal flora of mice fed with a conventional diet, followed by the construction of a mouse model with a high-fat and high-fructose diet to investigate the effects of Xihu Longjing on the prevention of lipid accumulation, intestinal barrier function impairment and intestinal microecological disorders in mice fed with high-fat and high-fructose diet. The results showed that Xihu Longjing tea soup inhibited the body mass gain and lipid accumulation in mice fed with a high-fat and high-fructose diet and effectively relieved metabolic disorders. When investigating the protective effects of Xihu Longjing on intestinal homeostasis in mice fed with a high-fat and high-fructose diet, it was found that Xihu Longjing tea soup treatment inhibited the expression of hypoxia inducible factor-1α (HIF-1α) and its target genes enolase-1 (ENO1)andlactate dehydrogenase A (LDHA) in the intestinal epithelial cells of mice. In addition, Xihu Longjing tea soup intervention reduced the abundance of intestinal bacteria of Firmicutes/Bacteroidota ratio and enriched the abundance of probiotic bacteria such as norank_f_Muribaculaceaein mice, and then the high-fat and high-fructose diet with low concentration of Xihu Longjing treatment enriched Lachnospiraceae bacteria and the high-fat and high-fructose diet with high concentration of Xihu Longjing treatment increased the relative abundance of Oscillospirales bacteria. The results provide a theoretical basis for Longjing tea to regulate fat accumulation by improving intestinal flora disorders, and provide theoretical support for the ability of tea consumption to improve intestinal health and play a role in fat reduction and body mass loss.