Publications of NIPGR Scientists

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Author: search.filters.author.Laxmi, AshveryaSubject: search.filters.subject.root

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    Striking the right chord: Signaling enigma during root gravitropism
    (Frontiers Media S.A., 2017) Singh, Manjul; Gupta, Aditi; Laxmi, Ashverya
    Plants being sessile can often be judged as passive acceptors of their environment. However, plants are actually even more active in responding to the factors from their surroundings. Plants do not have eyes, ears or vestibular system like animals, still they "know" which way is up and which way is down? This is facilitated by receptor molecules within plant which perceive changes in internal and external conditions such as light, touch, obstacles; and initiate signaling pathways that enable the plant to react. Plant responses that involve a definite and specific movement are called "tropic" responses. Perhaps the best known and studied tropisms are phototropism, i.e., response to light, and geotropism, i.e., response to gravity. A robust root system is vital for plant growth as it can provide physical anchorage to soil as well as absorb water, nutrients and essential minerals from soil efficiently. Gravitropic responses of both primary as well as lateral root thus become critical for plant growth and development. The molecular mechanisms of root gravitropism has been delved intensively, however, the mechanism behind how the potential energy of gravity stimulus converts into a biochemical signal in vascular plants is still unknown, due to which gravity sensing in plants still remains one of the most fascinating questions in molecular biology. Communications within plants occur through phytohormones and other chemical substances produced in plants which have a developmental or physiological effect on growth. Here, we review current knowledge of various intrinsic signaling mechanisms that modulate root gravitropism in order to point out the questions and emerging developments in plant directional growth responses. We are also discussing the roles of sugar signals and their interaction with phytohormone machinery, specifically in context of root directional responses.
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    Role of CIPK6 in root growth and auxin transport
    (Landes Bioscience, 2009) Tripathi, Vineeta; Syed, Nazia; Laxmi, Ashverya; Chattopadhyay, Debasis
    In our recent publication,1 we have shown that a T-DNA insertion in Arabidopsis CIPK6 gene encoding a CBL-interacting protein kinase caused reduction in expression of the gene and emergence of lateral roots. The change in phenotype in the mutant line was likely due to reduction in shoot-to-root acro- petal and the root tip basipetal auxin transport. Here we report identification of a homozygous knockout line of AtCIPK6 (atcipk6) with no detectable expression of the gene in normal growth condition. The knockout line exhibited considerable decrease in growth rate of the taproot as well as in emergence of lateral roots. The mutant line also showed reduction in the root tip basipetal and shoot-to-root acropetal auxin transport. Relative rate of auxin transport and the root phenotype of the atcipk6 closely matched with those of pgp4-1, an Arabidopsis line mutated in PGP4. This gene encodes an ABC integral membrane transporter, which functions in polar auxin transport. These observations strengthen our earlier proposal that CIPK6 is probably involved in polar auxin transport and indicate that it may function through the PGP4 auxin transporter.
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    CIPK6, a CBL-interacting protein kinase is required for development and salt tolerance in plant
    (Wiley-Blackwell, 2009) Tripathi, Vineeta; Parasuraman, Boominathan; Laxmi, Ashverya; Chattopadhyay, Debasis
    Calcineurin B-like proteins (CBL) and CBL-interacting protein kinases (CIPK) mediate plant responses to a variety of external stresses. Here we report that Arabidopsis CIPK6 is also required for the growth and development of plants. Phenotype of tobacco plants ectopically expressing a homologous gene (CaCIPK6) from the leguminous plant chickpea (Cicer arietinum) indicated its functional conservation. A lesion in AtCIPK6 significantly reduced shoot-to-root and root basipetal auxin transport, and the plants exhibited developmental defects such as fused cotyledons, swollen hypocotyls and compromised lateral root formation, in conjunction with reduced expression of a number of genes involved in auxin transport and abiotic stress response. The Arabidopsis mutant was more sensitive to salt stress compared to wild-type, while overexpression of a constitutively active mutant of CaCIPK6 promoted salt tolerance in transgenic tobacco. Furthermore, tobacco seedlings expressing the constitutively active mutant of CaCIPK6 showed a developed root system, increased basipetal auxin transport and hypersensitivity to auxin. Our results provide evidence for involvement of a CIPK in auxin transport and consequently in root development, as well as in the salt-stress response, by regulating the expression of genes.