Browsing by Author "Pandey, Bipin Kumar"

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Improvement of phosphate acquisition and utilization by a secretory purple acid phosphatase (OsPAP21b) in rice
(John Wiley & Sons, 2017) Mehra, Poonam; Pandey, Bipin Kumar; Giri, Jitender
Phosphate (Pi) deficiency in soil system is a limiting factor for rice growth and yield. Majority of the soil Phosphorus (P) is organic in nature; not readily available for root uptake. Low Pi inducible purple acid phosphatases (PAPs) are hypothesized to enhance the availability of Pi in soil and cellular system. However, information on molecular and physiological roles of rice PAPs is very limited. Here, we demonstrate the role of a novel rice PAP, OsPAP21b in improving plant utilization of organic-P. OsPAP21b was found to be under the transcriptional control of OsPHR2 and strictly regulated by plant Pi-status at both transcript and protein levels. Biochemically, OsPAP21b showed hydrolysis of several organophosphates at acidic pH and possessed sufficient thermostability befitting for high temperature rice ecosystems with acidic soils. Interestingly, OsPAP21b was revealed to be a secretory PAP and encodes a distinguishable major APase (acid phosphatase) isoform under low Pi in roots. Further, OsPAP21b overexpressing transgenics showed increased biomass, APase activity and P content both in hydroponics supplemented with organic-P sources and soil containing organic manure as sole P source. Additionally, overexpression lines depicted increased root length, biomass and lateral roots under low Pi while RNAi lines showed reduced root length and biomass as compared to WT. In light of these evidences, present study strongly proposes OsPAP21b as a useful candidate for improving Pi acquisition and utilization in rice.
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.