Genetic modification of rice for efficient nitrogen utilization

© 2021, Korean Society for Plant Biotechnology.Rice is a major crop worldwide, providing staple nourishment to half the global population. Improvements in rice productivity are essential to meet the needs of the growing global population. Rice productivity relies heavily on nitrogen (N) fertilization as N is crucial for rice growth and development and is the major limiting factor in most agricultural practices. However, excessive reliance on N fertilizer has adverse environmental impacts and increases production costs. Enhancing nitrogen use efficiency (NUE) is an urgent challenge in sustainable agriculture. This review summarizes the current understanding of N metabolism in rice and outlines the genetic modification of genes associated with N uptake and transport, assimilation, remobilization, and regulation to improve NUE. Recent research into NUE efficiency will facilitate the practical development of novel rice lines with increased productivity alongside low inputs of N fertilization.11Nsciescopuskc

OsASN1 Overexpression in Rice Increases Grain Protein Content and Yield under Nitrogen-Limiting Conditions

Nitrogen (N) is a major limiting factor affecting crop yield in unfertilized soil. Thus, cultivars with a high N use efficiency (NUE) and good grain protein content (GPC) are needed to fulfill the growing food demand and to reduce environmental burden. This is especially true for rice (Oryza sativa L.) that is cultivated with a high input of N fertilizer and is a primary staple food crop for more than half of the global population. Here, we report that rice asparagine synthetase 1 (OsASN1) is required for grain yield and grain protein contents under both N-sufficient (conventional paddy fields) and N-limiting conditions from analyses of knockout mutant plants. In addition, we show that overexpression (OX) of OsASN1 results in better nitrogen uptake and assimilation, and increased tolerance to N limitation at the seedling stage. Under field conditions, the OsASN1 OX rice plants produced grains with increased N and protein contents without yield reduction compared to wild-type (WT) rice. Under N-limited conditions, the OX plants displayed increased grain yield and protein content with enhanced photosynthetic activity compared to WT rice. Thus, OsASN1 can be an effective target gene for the development of rice cultivars with higher grain protein content, NUE, and grain yield under N-limiting conditions.11sci

Concurrent activation of OsAMT1;2 and OsGOGAT1 in rice leads to enhanced nitrogen use efficiency under nitrogen limitation

© 2020 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd. Nitrogen (N) is a major factor for plant development and productivity. However, the application of nitrogenous fertilizers generates environmental and economic problems. To cope with the increasing global food demand, the development of rice varieties with high nitrogen use efficiency (NUE) is indispensable for reducing environmental issues and achieving sustainable agriculture. Here, we report that the concomitant activation of the rice (Oryza sativa) Ammonium transporter 1;2 (OsAMT1;2) and Glutamate synthetase 1 (OsGOGAT1) genes leads to increased tolerance to nitrogen limitation and to better ammonium uptake and N remobilization at the whole plant level. We show that the double activation of OsAMT1;2 and OsGOGAT1 increases plant performance in agriculture, providing better N grain filling without yield penalty under paddy field conditions, as well as better grain yield and N content when plants are grown under N limiting in field conditions. Combining OsAMT1;2 and OsGOGAT1 activation provides a good breeding strategy for improving plant growth, nitrogen use efficiency and grain productivity, especially under nitrogen limitation, through the increment of both nitrogen uptake and assimilation11sci

Immune Modulatory Activities of Arginyl-Fructose (AF) and AF-Enriched Natural Products in In-Vitro and In-Vivo Animal Models

The immune system plays an important role in maintaining body homeostasis. Recent studies on the immune-enhancing effects of ginseng saponins have revealed more diverse mechanisms of action. Maillard reaction that occurs during the manufacturing processes of red ginseng produces a large amount of Amadori rearrangement compounds (ARCs), such as arginyl-fructose (AF). The antioxidant and anti-hyperglycemic effects of AF have been reported. However, the possible immune enhancing effects of non-saponin ginseng compounds, such as AF, have not been investigated. In this study the effects of AF and AF-enriched natural product (Ginofos, GF) on proliferation of normal mouse splenocytes were evaluated in vitro and male BALB/c mice models. The proliferation of splenocytes treated with mitogens (concanavalin A, lipopolysaccharide) were further increased by addition of AF (p < 0.01) or GF (p < 0.01), in a dose dependent manner. After the 10 days of oral administration of compounds, changes in weights of spleen and thymus, serum immunoglobulin, and expression of cytokines were measured as biomarkers of immune-enhancing potential in male BALB/c mice model. The AF or GF treated groups had higher weights of the thymus (0.94 ± 0.25 and 0.86 ± 0.18, p < 0.05, respectively) than that of cyclophosphamide treated group (0.59 ± 0.18). This result indicates that AF or AF-enriched extract (GF) increased humoral immunity against CY-induced immunosuppression. In addition, immunoglobulin contents and expression of cytokines including IgM (p < 0.01), IgG (p < 0.05), IL-2 (p < 0.01), IL-4 (p < 0.01), IL-6 (p < 0.01), and IFN-γ (p < 0.05) were also significantly increased by supplementation of AF or GF. These results indicate that AF has immune enhancing effects by activation of adaptive immunity via increase of expression of immunoglobulins and cytokines such as IgM, IgG, IL-2, IL-4, IL-6 and thereby proliferating the weight of thymus. Our findings provide a pharmacological rationale for AF-enriched natural products such as ginseng and red ginseng that can possibly have immune-enhancement potential and should be further evaluated

Natural variations at the Stay-Green gene promoter control lifespan and yield in rice cultivars

© 2020, The Author(s).Increased grain yield will be critical to meet the growing demand for food, and could be achieved by delaying crop senescence. Here, via quantitative trait locus (QTL) mapping, we uncover the genetic basis underlying distinct life cycles and senescence patterns of two rice subspecies, indica and japonica. Promoter variations in the Stay-Green (OsSGR) gene encoding the chlorophyll-degrading Mg++-dechelatase were found to trigger higher and earlier induction of OsSGR in indica, which accelerated senescence of indica rice cultivars. The indica-type promoter is present in a progenitor subspecies O. nivara and thus was acquired early during the evolution of rapid cycling trait in rice subspecies. Japonica OsSGR alleles introgressed into indica-type cultivars in Korean rice fields lead to delayed senescence, with increased grain yield and enhanced photosynthetic competence. Taken together, these data establish that naturally occurring OsSGR promoter and related lifespan variations can be exploited in breeding programs to augment rice yield11Nsciescopu