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Author: search.filters.author.Ranjan, RajeevStart date: 2020

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    The Mediator complex subunit, OsMED26_2, modulates plant growth, seed set and seed traits related to starch quality in rice
    (Elsevier B.V., 2026) Prusty, Ankita; Malik, Naveen; Ranjan, Rajeev; Agarwal, Pinky; Parida, Swarup K.; Kapoor, Sanjay; Tyagi, Akhilesh K.
    The Mediator (MED) complex is a multi-subunit structure crucial for RNA polymerase II-dependent transcription in eukaryotes. In this study, we investigated the function of a seed-preferential subunit of the rice Mediator complex, namely, OsMED26_2, for the first time. Knockdown of OsMED26_2 in rice reduced plant height and altered panicle morphology with shorter panicles, lesser branching, and fewer seeds per panicle. OsMED26_2 knockdown also led to shorter grains with shorter length and chalky endosperm. A significantly higher percentage of grains with chalkiness (PGWC) and degree of chalky endosperm (DCE) was observed in OsMED26_2 knockdown lines. OsMED26_2-knockdown seeds contained lower starch levels and altered proportions of amylose and amylopectin. Scanning electron microscopy further showed that these changes caused irregular, round, and loosely packed starch granules in the endosperm, contributing to the chalky phenotype. Decreased amylose content and increased grain chalkiness were corroborated by the downregulation of the Waxy (Wx) gene, which is involved in amylose synthesis, and altered expression of AMY3A, CHALK5, FLO4, GPA3, and SUSY3 genes, which regulate grain chalkiness. Our findings demonstrate that OsMED26_2 is critical in regulating panicle architecture, impacting yield, and modulating starch level and composition to control grain chalkiness and thereby suggesting its functional significance especially in manipulating yield attributing grain cooking quality traits of rice.
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    Natural alleles of Mediator subunit genes modulate plant height in chickpea
    (John Wiley & Sons, 2023) Malik, Naveen; Basu, Udita; Srivastava, Rishi; Daware, Anurag; Ranjan, Rajeev; Sharma, Akash; Thakro, Virevol; Mohanty, Jitendra K.; Jha, Uday Chand; Tripathi, Shailesh; Tyagi, Akhilesh K.; Parida, Swarup K.
    Plant height (PH) is an important plant architectural trait targeted during Green Revolution to enhance crop yields. Identification of genes and natural alleles governing plant height without compromising agronomic performance can fill the lacuna of knowledge connecting ideal plant architecture with maximum achievable yield in chickpea. Through coherent strategy involving genome-wide association study, QTL/fine mapping, map-based cloning, molecular haplotyping, and downstream functional genomics, the current study identified two Mediator subunit genes namely, CaMED23 and CaMED5b and their derived natural alleles/haplotypes underlying the major QTLs and trans-acting eQTLs regulating plant height in chickpea. Differential accumulation of haplotype-specific transcripts of these two Mediator genes in corresponding haplotype-introgressed near-isogenic lines (NILs) correlates negatively with the plant height trait. Quantitative as well as qualitative estimation based on histology, scanning electron microscopy, and histochemical assay unraveled the reduced lengths and cell sizes of internodes along with compromised lignin levels in dwarf/semi-dwarf chickpea NILs introgressed with superior CaMED23 and CaMED5b gene haplotypes. This observation, supported by global transcriptome profiling-based diminished expression of various phenylpropanoid pathway genes upstream of lignin biosynthesis in dwarf/semi-dwarf NILs, essentially links plant height with lignin accumulation. The identified molecular signatures in the Mediator subunit genes can be efficiently utilized to develop desirable dwarf/semi-dwarf-type chickpea cultivars without affecting their yield per plant via modulating lignin/phenylpropanoid biosynthesis.
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    OsCPK29 interacts with MADS68 to regulate pollen development in rice
    (Elsevier B.V., 2022) Ranjan, Rajeev; Malik, Naveen; Sharma, Shivam; Agarwal, Pinky; Kapoor, Sanjay; Tyagi, Akhilesh K.
    Pollen development and its germination are obligatory for the reproductive success of flowering plants. Calcium-dependent protein kinases (CPKs, also known as CDPKs) regulate diverse signaling pathways controlling plant growth and development. Here, we report the functional characterization of a novel OsCPK29 from rice, which is mainly expressed during pollen maturation stages of the anther. OsCPK29 exclusively localizes in the nucleus, and its N-terminal variable domain is responsible for retaining it in the nucleus. OsCPK29 knockdown rice plants exhibit reduced fertility, set fewer seeds, and produce collapsed non-viable pollen grains that do not germinate. Cytological analysis of anther semi-thin sections during different developmental stages suggested that pollen abnormalities appear after the vacuolated pollen stage. Detailed microscopic study of pollen grains further revealed that they were lacking the functional intine layer although exine layer was present. Consistent with that, downregulation of known intine development-related rice genes was also observed in OsCPK29 silenced anthers. Furthermore, it has been demonstrated that OsCPK29 interacts in vitro as well as in vivo with the MADS68 transcription factor which is a known regulator of pollen development. Therefore, phenotypic observations and molecular studies suggest that OsCPK29 is an important regulator of pollen development in rice.
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    Silencing of an ubiquitin ligase increases grain width and weight in indica rice
    (Frontiers Media S.A., 2021) Verma, Ankit; Prakash, Geeta; Ranjan, Rajeev; Tyagi, Akhilesh K.; Agarwal, Pinky
    Many quantitative trait loci (QTLs) have been identified by molecular genetic studies which control grain size by regulating grain width, length, and/or thickness. Grain width 2 (GW2) is one such QTL that codes for a RING-type E3 ubiquitin ligase and increases grain size by regulating grain width through ubiquitin-mediated degradation of unknown substrates. A natural variation (single-nucleotide polymorphism at the 346th position) in the functional domain-coding region of OsGW2 in japonica rice genotypes has been shown to cause an increase in grain width/weight in rice. However, this variation is absent in indica rice genotypes. In this study, we report that reduced expression of OsGW2 can alter grain size, even though natural sequence variation is not responsible for increased grain size in indica rice genotypes. OsGW2 shows high expression in seed development stages and the protein localizes to the nucleus and cytoplasm. Downregulation of OsGW2 by RNAi technology results in wider and heavier grains. Microscopic observation of grain morphology suggests that OsGW2 determines grain size by influencing both cell expansion and cell proliferation in spikelet hull. Using transcriptome analysis, upregulated genes related to grain size regulation have been identified among 1,426 differentially expressed genes in an OsGW2_RNAi transgenic line. These results reveal that OsGW2 is a negative regulator of grain size in indica rice and affects both cell number and cell size in spikelet hull.
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    Mediator subunit OsMED14_1 plays an important role in rice development
    (John Wiley & Sons, 2020) Malik, Naveen; Ranjan, Rajeev; Parida, Swarup K.; Agarwal, Pinky; Tyagi, Akhilesh K.
    Mediator, a multi‐subunit coactivator complex, regulates transcription in eukaryotes and is involved in diverse processes in Arabidopsis through its different subunits. Here, we have explored developmental aspects of one of the rice Mediator subunit gene OsMED14_1. We analyzed its expression pattern through RNA in‐situ hybridization and pOsMED14_1:GUS transgenics which showed its expression in roots, leaves, anthers and seeds prominently at younger stages, indicating possible involvement of this subunit in multiple aspects of rice development. To understand developmental roles of OsMED14_1 in rice, we generated and studied RNAi based knockdown rice plants which showed multiple effects including less height, narrower leaves and culms with reduced vasculature, lesser lateral root branching, defective microspore development, reduced panicle branching and seed set, and smaller seeds. Histological analyses showed that slender organs were caused by reduction in both cell number and cell size in OsMED14_1 knockdown plants. Flow cytometric analyses and expression analyses of cell‐cycle related genes revealed that defective cell‐cycle progression led to these defects. Expression analyses of auxin related genes and IAA immuno‐localization study indicated altered auxin level in these knockdown plants. Reduction of lateral root branching in knockdown plants was corrected by exogenous IAA supplement. OsMED14_1 physically interacts with transcription factors YABBY5, TDR and MADS29, possibly regulating auxin homeostasis and ultimately leading to lateral organ/leaf, microspore and seed development.