ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Transgenic Trifolium subterraneum expressing a phytase gene (phyA) from Aspergillus niger were generated. Five independently transformed lines showed an average 77-fold increase in exuded phytase activity in comparison with null segregant and wild-type controls. Unlike other phosphatases, exuded phytase activity was unaffected by P supply, verifying the constitutive expression of phyA. Transgenic T. subterraneum grown in agar with P supplied as phytate, took up 1.3- to 3.6-fold more P than controls and had equivalent P uptake to plants supplied with orthophosphate. This unique phenotype was compromised when the plants were grown in soil. None of the five lines showed increased shoot biomass or total P uptake in an unfertilized, low-P soil taken from under permanent pasture. With addition of P, one of the five transgenic lines had consistently greater P nutrition compared with control plants. Despite variable growth and P nutrition responses, P uptake per root length was on average greater for transgenic lines. Exudation of phytase by transgenic T. subterraneum allowed utilization of P from phytate in non-sorbing, sterile laboratory media, but was less effective when plants were grown in soil. Release of extracellular phytase is therefore not the only requirement for the acquisition of P from endogenous soil phytate by plants.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3040.2004.01225.x
