Publications of NIPGR Scientists

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    Root hair-specific transcriptome reveals response to low phosphorus in Cicer arietinum
    (Frontiers Media S.A., 2022) Kohli, Pawandeep Singh; Pazhamala, Lekha T; Mani, Balaji; Thakur, Jitendra K.; Giri, Jitender
    Root hairs (RH) are a single-cell extension of root epidermal cells. In low phosphorus (LP) availability, RH length and density increase thus expanding the total root surface area for phosphate (Pi) acquisition. However, details on genes involved in RH development and response to LP are missing in an agronomically important leguminous crop, chickpea. To elucidate this response in chickpea, we performed tissue-specific RNA-sequencing and analyzed the transcriptome modulation for RH and root without RH (Root-RH) under LP. Root hair initiation and cellular differentiation genes like RSL TFs and ROPGEFs are upregulated in Root-RH, explaining denser, and ectopic RH in LP. In RH, genes involved in tip growth processes and phytohormonal biosynthesis like cell wall synthesis and loosening (cellulose synthase A catalytic subunit, CaEXPA2, CaGRP2, and CaXTH2), cytoskeleton/vesicle transport, and ethylene biosynthesis are upregulated. Besides RH development, genes involved in LP responses like lipid and/or pectin P remobilization and acid phosphatases are induced in these tissues summarizing a complete molecular response to LP. Further, RH displayed preferential enrichment of processes involved in symbiotic interactions, which provide an additional benefit during LP. In conclusion, RH shows a multi-faceted response that starts with molecular changes for epidermal cell differentiation and RH initiation in Root-RH and later induction of tip growth and various LP responses in elongated RH.
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    Rice actin binding protein RMD controls crown root angle in response to external phosphate
    (Springer Nature, 2018) Huang, Guoqiang; Liang, Wanqi; Sturrock, Craig J.; Pandey, Bipin K.; Giri, Jitender; Mairhofer, Stefan; Wang, Daoyang; Muller, Lukas; Tan, Hexin; York, Larry M.; Yang, Jing; Song, Yu; Kim, Yu-Jin; Qiao, Yang; Xu, Jian; Kepinski, Stefan; Bennett, Malcolm J.; Zhang, Dabing
    Root angle has a major impact on acquisition of nutrients like phosphate that accumulate in topsoil and in many species; low phosphate induces shallower root growth as an adaptive response. Identifying genes and mechanisms controlling root angle is therefore of paramount importance to plant breeding. Here we show that the actin-binding protein Rice Morphology Determinant (RMD) controls root growth angle by linking actin filaments and gravity-sensing organelles termed statoliths. RMD is upregulated in response to low external phosphate and mutants lacking of RMD have steeper crown root growth angles that are unresponsive to phosphate levels. RMD protein localizes to the surface of statoliths, and rmd mutants exhibit faster gravitropic response owing to more rapid statoliths movement. We conclude that adaptive changes to root angle in response to external phosphate availability are RMD dependent, providing a potential target for breeders.
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    OsHAD1, a haloacid dehalogenase-like APase enhances phosphate accumulation
    (American Society of Plant Biologists, 2017) Pandey, Bipin Kumar; Mehra, Poonam; Verma, Lokesh; Bhadouria, Jyoti; Giri, Jitender
    Phosphorus (P) deficiency limits plant growth and crop yield. Since, plants can absorb only inorganic form of P (Pi), a large portion of soil P (organic and inorganic P complexes) remains largely unused. Here, we identified and characterized a PHR2 regulated; novel low Pi responsive haloacid dehalogenase (HAD)-like hydrolase, OsHAD1. While, OsHAD1 is a functional HAD protein having both acid phosphatase and phytase activity; it showed little homology with other known low Pi responsive HAD superfamily members. Recombinant OsHAD1 is highly active at acidic pH and dephosphorylates broad range of organic and inorganic P containing substrates including protein phosphates and Na-phytate. Exogenous application of recombinant OsHAD1 protein in growth media supplemented with phytate, led to marked increase in growth and total P content of Pi deficient WT rice seedlings. Further, overexpression of OsHAD1 in rice resulted in enhanced phosphatase activity, biomass, total and soluble P content in Pi deficient transgenic seedlings treated with phytate as restricted Pi source. Gene expression and metabolite profiling revealed enhanced Pi starvation responses such as upregulation of multiple genes involved in Pi uptake and solubilization, accumulation of organic acids, enhanced secretory phosphatase activity and depletion of ATP in overexpression lines as compared to WT. To elucidate the underlying regulatory mechanisms of OsHAD1, we performed in-vitro pull down assays which revealed association of OsHAD1 with protein kinases. We conclude that besides dephosphorylation of cellular organic-P, OsHAD1 in coordination with kinases may regulate phosphorylation status of downstream targets to accomplish Pi homeostasis under limited Pi supply.
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    Comparative morphophysiological analyses and molecular profiling reveal Pi-efficient strategies of a traditional rice genotype
    (Frontiers Media S.A., 2016) Mehra, Poonam; Pandey, Bipin K.; Giri, Jitender
    Phosphate (Pi) deficiency severely affects crop yield. Modern high yielding rice genotypes are sensitive to Pi deficiency whereas traditional rice genotypes are naturally compatible with low Pi ecosystems. However, the underlying molecular mechanisms for low Pi tolerance in traditional genotypes remain largely elusive. To delineate the molecular mechanisms for low Pi tolerance, two contrasting rice genotypes, Dular (low Pi tolerant), and PB1 (low Pi sensitive), have been selected. Comparative morphophysiological, global transcriptome and lipidome analyses of root and shoot tissues of both genotypes grown under Pi deficient and sufficient conditions revealed potential low Pi tolerance mechanisms of the traditional genotype. Most of the genes associated with enhanced internal Pi utilization (phospholipid remobilization) and modulation of root system architecture (RSA) were highly induced in the traditional rice genotype, Dular. Higher reserves of phospholipids and greater accumulation of galactolipids under low Pi in Dular indicated it has more efficient Pi utilization. Furthermore, Dular also maintained greater root growth than PB1 under low Pi, resulting in larger root surface area due to increased lateral root density and root hair length. Genes involved in enhanced low Pi tolerance of the traditional genotype can be exploited to improve the low Pi tolerance of modern high yielding rice cultivars.