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Front. Plant Sci. | doi: 10.3389/fpls.2018.00186

Heterologous expression of secreted bacterial BPP and HAP phytases in plants stimulates Arabidopsis thaliana growth on phytate

 Lia R. Valeeva1, Chuluuntsetseg Nyamsuren1,  Margarita R. Sharipova1 and  Eugene V. Shakirov1, 2*
  • 1Institute of Fundamental Medicine and Biology, Kazan (Volga region) Federal University, Russia
  • 2Integrative Biology, University of Texas at Austin, United States

Phytases are specialized phosphatases capable of releasing inorganic phosphate from myo-inositol hexakisphosphate (phytate), which is highly abundant in many soils. As inorganic phosphorus reserves decrease over time in many agricultural soils, genetic manipulation of plants to enable secretion of potent phytases into the rhizosphere has been proposed as a promising approach to improve plant phosphorus nutrition. Several families of biotechnologically important phytases have been discovered and characterized, but little data are available on which phytase families can offer the most benefits towards improving plant phosphorus intake. We have developed transgenic Arabidopsis thaliana plants expressing bacterial phytases PaPhyC (HAP family of phytases) and 168phyA (BPP family) under the control of root-specific inducible promoter Pht1;2. The effects of each phytase expression on growth, morphology and inorganic phosphorus accumulation in plants grown on phytate hydroponically or in perlite as the only source of phosphorus were investigated. The most enzymatic activity for both phytases was detected in cell wall-bound fractions of roots, indicating that these enzymes were efficiently secreted. Expression of both bacterial phytases in roots improved plant growth on phytate and resulted in larger rosette leaf area and diameter, higher phosphorus content and increased shoot dry weight, implying that these plants were indeed capable of utilizing phytate as the source of phosphorus for growth and development. When grown on phytate the HAP-type phytase outperformed its BPP-type counterpart for plant biomass production, though this effect was only observed in hydroponic conditions and not in perlite. Furthermore, we found no evidence of adverse side effects of microbial phytase expression in A. thaliana on plant physiology and seed germination. Our data highlight important functional differences between these members of bacterial phytase families and indicate that future crop biotechnologies involving such enzymes will require a very careful evaluation of phytase source and activity. Overall, our data suggest feasibility of using bacterial phytases to improve plant growth in conditions of phosphorus deficiency and demonstrate that inducible expression of recombinant enzymes should be investigated further as a viable approach to plant biotechnology.

Keywords: Phosphorus, phytate, phytase, transgenic plants, soil bacteria, Arabidopsis

Received: 23 Jan 2017; Accepted: 31 Jan 2018.

Edited by:

Sebastien Thomine, Centre national de la recherche scientifique (CNRS), France

Reviewed by:

Nicola Tomasi, University of Udine, Italy
Hatem ROUACHED, Institut National de la Recherche Agronomique (INRA), France  

Copyright: © 2018 Valeeva, Nyamsuren, Sharipova and Shakirov. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Eugene V. Shakirov, Kazan (Volga region) Federal University, Institute of Fundamental Medicine and Biology, Kazan, Republic of Tatarstan, Russia,