Volume 31 Issue 2
28 March 2024
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Research Papers
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Oriented Generation of Novel Thermo-Sensitive Genic Male Sterile Lines with Improved Grain Shape and Outcrossing Rate in Early-Season Rice
Zhang Huali, Chen Junyu, Li Ruiqing, Wang Huimei, Dai Dongqing, Liang Minmin, Wu Mingyue, Ma Liangyong
2024, 31(2): 129-133.  DOI: 10.1016/j.rsci.2023.11.006
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Protist and Plant Growth-Promoting Bacterium Interaction Alters GH3-2 Expression and Enhances Nutrient Content in Rice
Komal A. Chandarana, Natarajan Amaresan
2024, 31(2): 134-138.  DOI: 10.1016/j.rsci.2023.12.001
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High Power Microwave Treatment Impacts on Microbes in Rough Rice
Faith Ouma, Luthra Kaushik, Boreddy Sreenivasula, Oduola Abass, Griffiths G. Atungulu
2024, 31(2): 139-141.  DOI: 10.1016/j.rsci.2023.08.006
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Abiotic and Biotic Factors Controlling Grain Aroma along Value Chain of Fragrant Rice: A Review
Ayut Kongpun, Tonapha Pusadee, Pennapa Jaksomsak, Kawiporn Chinachanta, Patcharin Tuiwong, Phukjira Chan-In, Sawika Konsaeng, Wasu Pathom-Aree, Suchila Utasee, Benjamaporn Wangkaew, Chanakan Prom-U-Thai
2024, 31(2): 142-158.  DOI: 10.1016/j.rsci.2023.11.004
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The aroma of fragrant rice is one of the grain quality attributes that significantly influence consumer preferences and prices in world markets. The volatile compound 2-acetyl-1-pyrroline (2AP) is recognized as a key component of the aroma in fragrant rice. The variation in grain 2AP content among various fragrant rice varieties is associated with the expression of the badh2 gene, with 19 alleles having been identified so far. The grain 2AP content is strongly influenced by environmental and management factors during cultivation as well as post-harvest conditions. This review pinpointed the major abiotic and biotic factors that control grain 2AP content. Abiotic factors refer to water, temperature, light quality, fertilizer application (both macro- and micro-nutrients), and soil properties, including salinity, while biotic factors include microorganisms that produce aromatic compounds, thus influencing the grain aroma in fragrant rice. Post-harvest management, including storage and drying conditions, can significantly impact the grain 2AP content, and proper post-harvest conditions can intensify the grain aroma. This review suggests that there are rice varieties that can serve as potential sources of genetic material for breeding rice varieties with high grain aroma content. It offers an overview of recent research on the major factors affecting the aroma content in fragrant rice. This knowledge will facilitate further research on the production of high-quality rice to meet the demands of farmers and consumers.

Methane Emission from Rice Fields: Necessity for Molecular Approach for Mitigation
Sujeevan Rajendran, Hyeonseo Park, Jiyoung Kim, Soon Ju Park, Dongjin Shin, Jong-Hee Lee, Young Hun Song, Nam-Chon Paek, Chul Min Kim
2024, 31(2): 159-178.  DOI: 10.1016/j.rsci.2023.10.003
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Anthropogenic methane emissions are a leading cause of the increase in global average temperatures, often referred to as global warming. Flooded soils play a significant role in methane production, where the anaerobic conditions promote the production of methane by methanogenic microorganisms. Rice fields contribute a considerable portion of agricultural methane emissions, as rice plants provide both factors that enhance and limit methane production. Rice plants harbor both methane- producing and methane-oxidizing microorganisms. Exudates from rice roots provide source for methane production, while oxygen delivered from the root aerenchyma enhances methane oxidation. Studies have shown that the diversity of these microorganisms depends on rice cultivars with some genes characterized as harboring specific groups of microorganisms related to methane emissions. However, there is still a need for research to determine the balance between methane production and oxidation, as rice plants possess the ability to regulate net methane production. Various agronomical practices, such as fertilizer and water management, have been employed to mitigate methane emissions. Nevertheless, studies correlating agronomic and chemical management of methane with productivity are limited. Moreover, evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence of coordinated breeding programs. Research has indicated that phenotypic characteristics, such as root biomass, shoot architecture, and aerenchyma, are highly correlated with methane emissions. This review discusses available studies that involve the correlation between plant characteristics and methane emissions. It emphasizes the necessity and importance of breeding low-methane-emitting rice varieties in addition to existing agronomic, biological, and chemical practices. The review also delves into the ideal phenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques, drawing from studies conducted with diverse varieties, mutants, and transgenic plants.

Drought-Tolerant Rice at Molecular Breeding Eras: An Emerging Reality
Zhu Chengqi, Ye Yuxuan, Qiu Tian, Huang Yafan, Ying Jifeng, Shen Zhicheng
2024, 31(2): 179-189.  DOI: 10.1016/j.rsci.2023.11.005
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Rice (Oryza sativa L.) stands as the most significantly influential food crop in the developing world, with its total production and yield stability affected by environmental stress. Drought stress impacts about 45% of the world’s rice area, affecting plants at molecular, biochemical, physiological, and phenotypic levels. The conventional breeding method, predominantly employing single pedigree selection, has been widely utilized in breeding numerous drought-tolerant rice varieties since the Green Revolution. With rapid progress in plant molecular biology, hundreds of drought-tolerant QTLs/genes have been identified and tested in rice crops under both indoor and field conditions. Several genes have been introgressed into elite germplasm to develop commercially accepted drought-tolerant varieties, resulting in the development of several drought-tolerant rice varieties through marker-assisted selection and genetically engineered approaches. This review provides up-to-date information on proof-of-concept genes and breeding methods in the molecular breeding era, offering guidance for rice breeders to develop drought-tolerant rice varieties.

Research Papers
OsbZIP53 Negatively Regulates Immunity Response by Involving in Reactive Oxygen Species and Salicylic Acid Metabolism in Rice
Wu Lijuan, Han Cong, Wang Huimei, He Yuchang, Lin Hai, Wang Lei, Chen Chen, E Zhiguo
2024, 31(2): 190-202.  DOI: 10.1016/j.rsci.2023.12.002
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The basic region/leucine zipper (bZIP) transcription factors play important roles in plant development and responses to abiotic and biotic stresses. OsbZIP53 regulates resistance to Magnaporthe oryzae in rice by analyzing APIP5-RNAi transgenic plants. To further investigate the biological functions of OsbZIP53, we generated osbzip53 mutants using CRISPR/Cas9 editing and also constructed OsbZIP53 over-expression transgenic plants. Comprehensive analysis of phenotypical, physiological, and transcriptional data showed that knocking-out OsbZIP53 not only improved disease resistance by inducing a hypersensitivity response in plants, but also regulated the immune response through the salicylic acid pathway. Specifically, disrupting OsbZIP53 increased H2O2 accumulation by promoting reactive oxygen species generation through up-regulation of several respiratory burst oxidase homologs (Osrboh genes) and weakened H2O2 degradation by directly targeting OsMYBS1. In addition, the growth of osbzip53 mutants was seriously impaired, while OsbZIP53 over-expression lines displayed a similar phenotype to the wild type, suggesting that OsbZIP53 has a balancing effect on rice immune response and growth.

Carbon Catabolite Repressor UvCreA is Required for Development and Pathogenicity in Ustilaginoidea virens
Xie Shuwei, Shi Huanbin, Wen Hui, Liu Zhiquan, Qiu Jiehua, Jiang Nan, Kou Yanjun
2024, 31(2): 203-214.  DOI: 10.1016/j.rsci.2023.11.008
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The rice false smut disease, caused by Ustilaginoidea virens, has emerged as a significant global threat to rice production. The mechanism of carbon catabolite repression plays a crucial role in the efficient utilization of carbon nutrients and enzyme regulation in the presence of complex nutritional conditions. Although significant progress has been made in understanding carbon catabolite repression in fungi such as Aspergillus nidulans and Magnaporthe oryzae, its role in U. virens remains unclear. To address this knowledge gap, we identified UvCreA, a pivotal component of carbon catabolite repression, in U. virens. Our investigation revealed that UvCreA localized to the nucleus. Deletion of UvCreA resulted in decreased growth and pathogenicity in U. virens. Through RNA-seq analysis, it was found that the knockout of UvCreA led to the up-regulation of 514 genes and down-regulation of 640 genes. Moreover, UvCreA was found to be involved in the transcriptional regulation of pathogenic genes and genes associated with carbon metabolism in U. virens. In summary, our findings indicated that UvCreA is important in fungal development, virulence, and the utilization of carbon sources through transcriptional regulation, thus making it a critical element of carbon catabolite repression.

Analysis of RNA Recognition and Binding Characteristics of OsCPPR1 Protein in Rice
Zheng Shaoyan, Chen Junyu, Li Huatian, Liu Zhenlan, Li Jing, Zhuang Chuxiong
2024, 31(2): 215-225.  DOI: 10.1016/j.rsci.2023.11.011
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Pentatricopeptide repeat (PPR) proteins represent one of the largest protein families in plants and typically localize to organelles like mitochondria and chloroplasts. By contrast, CYTOPLASM- LOCALIZED PPR1 (OsCPPR1) is a cytoplasm-localized PPR protein that can degrade OsGOLDEN- LIKE1 (OsGLK1) mRNA in the tapetum of rice anther. However, the mechanism, by which OsCPPR1 recognizes and binds to OsGLK1 transcripts, remains unknown. Through protein structure prediction and macromolecular docking experiments, we observed that distinct PPR motif structures of OsCPPR1 exhibited varying binding efficiencies to OsGLK1 RNA. Moreover, RNA-electrophoretic mobility shift assay experiment demonstrated that the recombinant OsCPPR1 can directly recognize and bind to OsGLK1 mRNA in vitro. This further confirmed that the mutations in the conserved amino acids in each PPR motif resulted in loss of activity, while truncation of OsCPPR1 decreased its binding efficiency. These findings collectively suggest that it may require some co-factors to assist in cleavage, a facet that warrants further exploration in subsequent studies.

Causal Analysis Between Rice Growth and Cadmium Accumulation and Transfer under Arbuscular Mycorrhizal Inoculation
Zhao Ting, Wang Li, Yang Jixian, Ma Fang
2024, 31(2): 226-236.  DOI: 10.1016/j.rsci.2023.10.004
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Cadmium (Cd) contamination in rice has been a serious threat to human health. To investigate the effects of arbuscular mycorrhizal fungi (AMF) on the Cd translocation in rice, a controlled pot experiment was conducted. The results indicated that AMF significantly increased rice biomass, with an increase of up to 40.0%, particularly in root biomass by up to 68.4%. Notably, the number of prominent rice individuals also increased, and their plasticity was enhanced following AMF inoculation. AMF led to an increase in the net photosynthetic rate and antioxidant enzyme activity of rice. In the AMF treatment group, the Cd concentration in the rice roots was significantly higher (19.1%‒68.0%) compared with that in the control group. Conversely, the Cd concentration in the rice seeds was lower in the AMF treatment group, indicating that AMF facilitated the sequestration of Cd in rice roots and reduced Cd accumulation in the seeds. Path coefficients varied across different treatments, suggesting that AMF inoculation reduced the direct impact of soil Cd concentration on the total Cd accumulation in seeds. The translocation of Cd was consistently associated with simultaneous growth dilution and compensatory accumulation as a result of mycorrhizal effects. Our study quantitatively analyzed this process through path analysis and clarified the causal relationship between rice growth and Cd transfer under the influence of AMF.