Publications of NIPGR Scientists

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Author: search.filters.author.Ranjan, AashishSubject: search.filters.subject.Photosynthesis

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Now showing 1 - 5 of 5
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    Optimizing photosynthesis by targeting light signaling transcriptional networks
    (Oxford University Press, 2026) Sanyal, Rajarshi; Ranjan, Aashish
    Light serves as a crucial environmental signal for plants besides providing energy for photosynthesis. Photomorphogenesis, light-induced plant developmental responses, involves photoreceptors perceiving light signals to initiate signaling cascades with downstream transcriptional networks. Moreover, light is also absorbed by photopigments to drive photosynthetic light reactions, providing energy for growth and metabolism. As light serves as a primary cue for both photomorphogenesis and photosynthesis, a crosstalk between the two processes is anticipated. While transcriptional regulation of photomorphogenesis is investigated in detail, our understanding of the transcriptional control of photosynthesis remains limited. Recent studies have shown the involvement of photoreceptors and key light-signaling transcription factors, such as PHYTOCHROME-INTERACTING FACTORs (PIFs) and ELONGATED HYPOCOTYL 5 (HY5), in the regulation of photosynthesis. This review not only highlights the transcriptional regulation of photosynthesis but also provides a broader perspective on the involvement of key transcription factors of photomorphogenesis in the regulation of photosynthesis. The review further discusses strategies to investigate and manipulate the light signaling transcriptional regulatory networks for optimizing photosynthetic efficiency.
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    Integration of metabolite and transcriptome profiles of cultivated and wild rice to unveil gene regulatory networks and key genes determining rice source and sink strength
    (Springer Nature Publishing AG, 2025) Singh, Anuradha; Mathan, Jyotirmaya; Dwivedi, Aditi; Rani, Ruchi; Ranjan, Aashish
    Targeting source and sink strength for crop yield increase requires a comprehensive genetic and metabolic understanding of desirable source and sink features. We performed comprehensive metabolite and transcriptomic comparisons of the photosynthetic flag leaves and milky-stage developing grains of two cultivated rice varieties (Oryza sativa L. ssp. Indica cv. IR64 and Oryza sativa L. ssp. Japonica cv. Nipponbare) and two wild rice accessions (Oryza rufipogon and Oryza australiensis). The selected wild rice accessions had stronger source strength as evidenced by a higher photosynthesis rate and more abundance of primary metabolites in the photosynthetic leaves than the cultivated varieties. In contrast, cultivated varieties had efficient sink as grains were bigger and accumulated more sugars, amino acids, and fatty acids than the selected wild rice. Transcriptomic analyses identified 9,309 genes for efficient source in wild rice, enriched for biological pathways related to photosynthesis, carbohydrate metabolism, and sucrose transport. 7,062 genes, enriched for starch biosynthesis and lipid metabolism, were associated with the efficient sink strength in the cultivated varieties. Gene co-expression networks showed 267 hub genes for source strength in wild rice that included important genes for photosynthetic reactions and sucrose metabolism. 196 hub genes for sink strength in cultivated rice included genes involved in sucrose, amino acid, and fatty acid metabolism. Gene co-expression modules further identified the candidate transcription regulators, such as zinc finger proteins and NAC for source strength and MYB55/80 and MADS64 for sink strength. Moreover, our analyses suggested a complex interplay of phytohormones regulating rice source and sink strength.
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    Revisiting development and physiology of wild rice relatives for crop improvement and climate resilience
    (Springer Nature Publishing AG, 2025) Mathan, Jyotirmaya; Dwivedi, Aditi; Ranjan, Aashish
    Increasing rice yield and productivity under changing climatic conditions is imperative for sustainable food security, given rice is a major staple crop around the world. Natural variation in crop plants, including wild relatives, offers remarkable genetic variability to explore the desirable developmental and physiologic traits for crop improvement. Wild relatives of rice, with distinct developmental and physiologic features compared to cultivated varieties, are the potential genetic and genomic resource for rice yield increases under changing climate. A thorough genetic basis of rice developmental and architectural changes during domestication is now established with the identification and characterization of domestication genes. Photosynthetically efficient wild rice accessions, with desirable developmental, physiologic, and metabolic traits, have been identified in recent years that could be instrumental for rice improvement. While several abiotic and biotic stress-tolerant wild relatives of rice along with the associated genetic loci have been identified over the years, a comprehensive insight into the desirable developmental and physiologic attributes of the wild rice is limited. Moreover, the usage of wild rice is not streamlined in rice-improvement programs due to genetic and genomic constraints. In this review, we summarize the desirable developmental and physiologic features of wild rice species that can be exploited for combining yield increases with climate resilience in rice-improvement programs.
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    High photosynthesis rate in two wild rice species is driven by leaf anatomy mediating high Rubisco activity and electron transport rate
    (Oxford University Press, 2021) Mathan, Jyotirmaya; Singh, Anuradha; Jathar, Vikram; Ranjan, Aashish
    The importance of increasing photosynthetic efficiency for sustainable crop yield increases to feed the growing world population is well recognized. The natural genetic variation for leaf photosynthesis in crop plants is largely unexploited for increasing genetic yield potential. The genus Oryza, including cultivated rice and wild relatives, offers tremendous genetic variability to explore photosynthetic differences, and underlying biochemical, photochemical, and developmental bases. We quantified leaf photosynthesis and related physiological parameters for six cultivated and three wild rice genotypes, and identified photosynthetically efficient wild rice accessions. Fitting A/Ci curves and biochemical analyses showed that the leaf photosynthesis in cultivated rice varieties, IR64 and Nipponbare, was limited due to leaf nitrogen content, Rubisco activity, and electron transport rate compared to photosynthetically efficient accessions of wild rice Oryza australiensis and Oryza latifolia. The selected wild rice accessions with high leaf photosynthesis per unit area had striking anatomical features, such as larger mesophyll cells with more chloroplasts, fewer mesophyll cells between two consecutive veins, and higher mesophyll cell and chloroplast surface area exposed to intercellular space. Our results show the existence of desirable variations in Rubisco activity, electron transport rate, and leaf anatomical features in the rice system itself that could be targeted for increasing the photosynthetic efficiency of cultivated rice varieties.
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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.