Institutional Publications

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    Differential response of rice genotypes to nitrogen availability is associated with the altered nitrogen metabolism and ionomic balance
    (Elsevier B.V., 2022) Kumari, Priyanka; Devi, Loitongbam Lorinda; Kumar, Amresh; Pandey, Ashutosh; Sinha, Subodh Kumar; Singh, Amar Pal
    Nitrogen (N) uptake and its assimilation are crucial steps for plant growth and productivity. Plant's N balance largely depends on nitrate (NO3-) and ammonium (NH4+) forms present in the rhizosphere. Due to the fluctuating and heterogeneous availability of these N forms in the soils, plants encounter low to N deficiency. In contrast to low nitrogen, high N in the form of ammonium (NH4+) severely hampers plant development and causes NH4+ toxicity. In this study, we assessed eleven rice genotypes under sufficient (SN) and low N (LN) conditions. From the analysis, we identified a rice genotype, PB1, which is hypersensitive to SN and showed reduced root and shoot growth. In contrast to the SN condition, PB1 showed improved growth performance under the LN condition. Our data show that compromised growth of PB1 under SN condition is associated with increased activity of N responsive genes such as OsAMT1.1, OsAMT2.3, OsAMT3.1 and OsAMT3.2, OsNRT1.1A and OsNRT1.1B. Strikingly, LN treatment improved the root and shoot biomass with a concomitant increase in levels of NO3- and NH4+ transporter genes along with an increase in shoot: root NO3- ratio. Additionally, we show that increased levels of N in PB1 under SN condition are associated with the enhanced activity of the GS-GOGAT pathway. Further, our ionomic analysis highlighted the role of N-defined Fe accumulation which is partially associated with the N toxicity. Taken together, our study led to identifying a rice genotype (Oryza sativa L.) which is associated with enhanced N levels and assimilation and could be used for raising N use efficient rice varieties using breeding approaches.
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    Sucrose transport and metabolism control carbon partitioning between stem and grain in rice
    (Oxford University Press, 2021) Mathan, Jyotirmaya; Singh, Anuradha; Ranjan, Aashish
    The source-sink relationship is key to overall crop performance. Detailed understanding of the factors that determine source-sink dynamics is imperative for the balance of biomass and grain yield in crop plants. We investigated the differences in the source-sink relationship between a cultivated rice Oryza sativa cv. Nipponbare and a wild rice Oryza australiensis that show striking differences in biomass and grain yield. Oryza australiensis, accumulating higher biomass, not only showed higher photosynthesis per unit leaf area but also exported more sucrose from leaves than Nipponbare. However, grain features and sugar levels suggested limited sucrose mobilization to the grains in the wild rice due to vasculature and sucrose transporter functions. Low cell wall invertase activity and high sucrose synthase cleavage activity followed by higher expression of cellulose synthase genes in Oryza australiensis stem utilized photosynthates preferentially for the synthesis of structural carbohydrates, resulting in high biomass. In contrast, the source-sink relationship favored high grain yield in Nipponbare via accumulation of transitory starch in the stem, due to higher expression of starch biosynthetic genes, which is mobilized to panicles at the grain filling stage. Thus, vascular features, sucrose transport, and functions of sugar metabolic enzymes explained the differences in the source-sink relationship between Nipponbare and Oryza australiensis.