title: Expression of a fungal phytase gene in Nicotiana tabacum improves phosphorus nutrition of plants grown in amended soils.
abstract: Transgenic Nicotiana tabacum plants expressing a chimeric phytase gene (ex::phyA) from the soil fungus Aspergillus niger were generated. Three independently transformed lines showed increased extracellular phytase activity compared with a vector control and wild-type plants, both of which had no detectable extracellular phytase. Transgenic N. tabacum plants grown in sterile agar supplied with phosphorus (P) as phytate accumulated 3.7-fold more P than vector control plants. Despite this, the expression of ex::phyA in plants did not lead to an improved accumulation of P from two unamended P-deficient soils. However, when soils were amended with either phytate or phosphate and lime, transgenic plants accumulated up to 52% more P than controls. Positive responses by transgenic plants were, in some instances, coincident with a putative increase in soil phytate. We conclude that the development of plants that exude phytase to the soil may not ensure improved plant P nutrition, as the availability of phytate in the soil also appears to be critical. Nevertheless, if plants that express ex::phyA are combined with soil amendments that promote the availability of phytate, there is the potential to enhance the P nutrition of crop plants and to improve the efficiency of P fertilizer use in agricultural systems.
authors.affiliation: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: George
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Simpson
authors.forename: Paul A
authors.initials: PA
authors.lastname: Hadobas
authors.forename: Alan E
authors.initials: AE
authors.lastname: Richardson