Publications of NIPGR Scientists

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    Cytokinin-mediated repression of anthocyanin biosynthesis in banana fruits
    (John Wiley & Sons, 2025) Rajput, Ruchika; Tyagi, Shivi; Anchal, Kumar; Singh, Samar; Laxmi, Ashverya; Misra, Prashant; Pandey, Ashutosh
    Anthocyanins are pigments responsible for vibrant plant colors and play vital roles in plant physiology. This study compares two banana cultivars, Grand Naine (GN) and Red Banana (RB), which exhibit significant differences in anthocyanin pigmentation. Transcriptomic profiling of peel (PL) and pulp (PP) tissues revealed cytokinin-responsive type-B response regulators (RRs), MaRR_B9 and MaRR_B12, as key modulators of anthocyanin biosynthesis. Cytokinin treatment of PP tissues increased the expression of MaRR_B9 and MaRR_B12, while significantly reducing the expression of dihydroflavanol reductase (MaDFR1, MaDFR2) and anthocyanidin synthase (MaANS) genes along with anthocyanin content. Through a combination of physiological, molecular, and biochemical analyses, we demonstrate that MaRR_B9 and MaRR_B12 exert direct regulatory control over key structural genes of anthocyanin biosynthesis, MaDFRs and MaANS. Additionally, a type B-RRs motif (AGATT) was identified in the promoter regions of MaDFR2 and MaANS, suggesting that MaRRs might directly regulate the transcription of MaDFR2 and MaANS. MaRR_B9 and MaRR_B12 interact with the promoters of MaDFR2 and MaANS, repressing these genes in vivo. Overexpression of MaRR_B9 and MaRR_B12 in banana fruits leads to a reduction in anthocyanin content, notably the cyanidin derivative, accompanied by altered expression patterns of MaDFRs and MaANS. Thus, the present study identifies MaRR_B9 and MaRR_B12 as novel regulators of anthocyanin biosynthesis in banana and provides further evidence that the cytokinin regulatory network modifies anthocyanin accumulation in plants. In conclusion, our findings reveal new molecular targets, in the form of MaRRs, for the genetic optimization aimed at enhancing anthocyanin content, stress resilience, and nutritional value in crop plants.
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    Dynamics of miRNA mediated regulation of legume symbiosis
    (John Wiley & Sons, 2021) Tiwari, Manish; Pandey, Vimal; Singh, Baljinder; Bhatia, Sabhyata
    Symbiotic nitrogen fixation in legume nodules is important in soils with low nitrogen availability. The initiation and sustainability of symbiosis requires cellular reprogramming that involves the miRNA‐mediated inhibition or activation of specific nodulation genes. The high‐throughput sequencing of small RNA libraries has identified miRNAs and their targets, which are the major players in the post‐transcriptional gene regulation (PTGS) of the different stages of legume‐rhizobia symbiosis ranging from bacterial colonization and organogenesis to symbiotic nitrogen fixation. Here we present an overview of information obtained from the miRNA libraries from nodulating tissues that have been sequenced to date. The functional analysis of miRNAs has revealed roles in phytohormone homeostasis and spatio‐temporal regulation, as well as the mobility of miRNAs and their functions in shoot to root signalling that affects diverse functions, including bacterial entry, meristem division and differentiation, nitrogen fixation and senescence. Furthermore, small RNA fragments of rhizobial origin repress complementary plant mRNAs. We also consider the roles of miRNAs in determinate or indeterminate nodules. Taken together, this overview confirms that miRNAs are master regulators of the legume‐rhizobia symbiosis.
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    Root-specific expression of chickpea cytokinin oxidase/dehydrogenase 6 leads to enhanced root growth, drought tolerance and yield without compromising nodulation
    (John Wiley & Sons, 2020) Khandal, Hitaishi; Gupta, Santosh Kumar; Dwivedi, Vikas; Mandal, Drishti; Sharma, Nilesh Kumar; Vishwakarma, Niraj Kumar; Pal, Lalita; Choudhary, Megha; Francis, Aleena; Malakar, Paheli; Singh, Nagendra Pratap; Sharma, Kapil; Sinharoy, Senjuti; Singh, Narendra Pratap; Sharma, Rameshwar; Chattopadhyay, Debasis
    Cytokinin group of phytohormones regulate root elongation and branching during post‐embryonic development. Cytokinin degrading enzymes cytokinin oxidases/dehydrogenases (CKXs) have been deployed to investigate biological activities of cytokinin and to engineer root growth. We expressed chickpea cytokinin oxidase 6 (CaCKX6) under the control of a chickpea root‐specific promoter of CaWRKY31 in Arabidopsis thaliana and chickpea having determinate and indeterminate growth patterns, respectively, to study the effect of cytokinin depletion on root growth and drought tolerance. Root‐specific expression of CaCKX6 led to a significant increase in lateral root number and root biomass in Arabidopsis and chickpea without any penalty to vegetative and reproductive growth of shoot. Transgenic chickpea lines showed increased CKX activity in root. Soil‐grown advanced chickpea transgenic lines exhibited higher root‐to‐shoot biomass ratio and enhanced long‐term drought tolerance. These chickpea lines were not compromised in root nodulation and nitrogen fixation. The seed yield in some lines was up to 25% higher with no penalty in protein content. Transgenic chickpea seeds possessed higher levels of zinc, iron, potassium and copper. Our results demonstrated the potential of cytokinin level manipulation in increasing lateral root number and root biomass for agronomic trait improvement in an edible legume crop with indeterminate growth habit.
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    CBL-interacting protein kinase 25 contributes to root meristem development
    (Oxford University Press, 2019) Meena, Mukesh Kumar; Vishwakarma, Niraj Kumar; Tripathi, Vineeta; Chattopadhyay, Debasis
    Coordination of auxin and cytokinin activities determines root meristem size during post-embryonic development. Calcineurin B-like proteins (CBLs) and their interacting protein kinases (CIPKs) constitute signaling modules that relay calcium signals. Here we report that CIPK25 is involved in regulating the root meristem size. Arabidopsis plants lacking CIPK25 expression displayed a short root phenotype and a slower root growth rate with less meristem cells. This phenotype was rescued by restoration of CIPK25 expression. CIPK25 interacted with CBL4 and -5, and displayed a strong gene expression in the flower and root except in the cell proliferation domain in the root apical meristem. Its expression in root was positively and negatively regulated by auxin and cytokinin, respectively. cipk25 T-DNA insertion line was compromised in auxin transport and auxin-responsive promoter activity. cipk25 mutant line showed altered expression of auxin efflux carriers and an Aux/IAA family gene SHY2. Decreased PIN1 and PIN2 expression in cipk25 mutant line was completely restored when combined with SHY2 loss-of-function mutation resulting in recovery of root growth. SHY2 and PIN1 expression was partially regulated by cytokinin even in absence of CIPK25, suggesting existence of CIPK25-independent cytokinin signaling pathway(s) as well. Our results suggested a role of CIPK25 in root meristem development.
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    The interaction between glucose and cytokinin signaling in controlling Arabidopsis thaliana seedling root growth and development
    (Taylor & Francis Group, 2017) Kushwah, Sunita; Laxmi, Ashverya
    Cytokinin (CK) and glucose (GLC) control a number of common responses in plants. There is an extensive overlap between CK and GLC signal transduction pathways in Arabidopsis. Physiologically, both GLC and CK could regulate root length in light. CK interacts with GLC via HXK1 dependent pathway for root length control. Wild-type (WT) roots cannot elongate in the GLC free medium while CK-receptor mutant ARABIDOPSIS HISTIDINE KINASE4 (ahk4) and type B ARR triple mutant ARABIDOPSIS RESPONSE REGULATOR1, 10,11 (arr1, 10,11) roots could elongate even in the absence of GLC as compared to the WT. The root hair initiation was also found defective in CK signaling mutants ahk4, arr1,10,11 and arr3,4,5,6,8,9 on increasing GLC concentration (up to 3%); and lesser number of root hairs were visible even at 5% GLC as compared to the WT. Out of 941 BAP regulated genes, 103 (11%) genes were involved in root growth and development. Out of these 103 genes, 60 (58%) genes were also regulated by GLC. GLC could regulate 5736 genes, which include 327 (6%) genes involved in root growth and development. Out of these 327 genes, 60 (18%) genes were also regulated by BAP. Both GLC and CK signaling cannot alter root length in light in auxin signaling mutant AUXIN RESPONSE3/INDOLE-3-ACETIC ACID17 (axr3/iaa17) suggesting that they may involve auxin signaling component as a nodal point. Therefore CK- and GLC- signaling are involved in controlling different aspects of root growth and development such as root length, with auxin signaling components working as downstream target.
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    Glucose and phytohormone interplay in controlling root directional growth in Arabidopsis
    (Taylor & Francis Group, 2014) Singh, Manjul; Gupta, Aditi; Laxmi, Ashverya
    Sensing and responding toward gravity vector is a complicated and multistep process. Gravity is a constant factor feeding plants with reliable information for the spatial orientation of their organs. Auxin, cytokinin, ethylene and BRs have been the most explored hormones in relation to gravitropism. We have previously shown that glucose (Glc) could promote brassinosteroid (BR) signaling thereby inducing changes in root directional growth. Auxin signaling and polar transport components are also involved in Glc induced changes in root directional growth. Here, we provide evidence for involvement of cytokinin and ethylene signaling components in regulation of root directional growth downstream to Glc and BR. Altogether, Glc mediated change in root direction is an adaptive feature which is a result of a collaborative effort integrating phytohormonal signaling cues.
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    Cytokinin-induced root growth involves actin filament reorganization
    (Landes Bioscience, 2011) Kushwah, Sunita; Jones, Alan M.; Laxmi, Ashverya
    Root architecture is developmentally plastic and affected by many intrinsic factors (e.g. plant hormones) and extrinsic factors (e.g. touch, gravity) in order to maximize nutrient and water acquisition. We have recently shown that asymmetrical exposure of cytokinin (CK) at the root tip causes root growth directional changes that is dependent on ethylene signaling and is potentiated by glucose signaling. Auxin homeostasis as maintained by auxin signaling and transport is also involved in CK-induced root cell elongation and differential growth. The signaling pathways eventually converge at actin filament organization since actin filament organization inhibitor latrunculin B (Lat B) can also induce similar growth. We, show that CK can actually alter actin filament organization as seen in actin binding protein 35S::GFP-ABD2-GFP transgenic lines as is also altered by auxin polar transport inhibitor 1-N-naphthylphthalamic acid (NPA) and Lat B in different manners.