Heterologous expression of genes encoding extracellular enzymes to improve access to organic forms of mineral nutrients

While breeding beneficial traits into commercial germplasm and/or managing the agricultural system to maximise the benefit of soil ecology are possible, a more direct route to improve resource capture by plants is to express beneficial genes in crops directly.

In collaboration with Dr Alan Richardson (CSIRO, Australia) we have expressed extracellular phytase genes in plants, in an attempt to improve P acquisition from organic compounds in the soil. Recent experiments have compared plants grown in soils amended with monogastric animal manures (pigs and poultry) which are thought to contain high concentrations of phytate (the substrate of phytase), with those grown in soils amended with low-phytate manure from ruminants (cattle). Plants expressing extracellular phytases had greater P-uptake than untransformed controls when grown in soils amended with high-phytate manures, but had no advantage in soils amended with low-phytate manures.

These results suggest that it may be possible to enhance P-acquisition by crops by increasing rhizosphere phytase activity. Other work done by our group with these plants has also demonstrated that the expression of phytase in plants does not impact on other associated organisms in the system including rhizosphere bacteria, mycorrhizal fungi and aphids.

The research being performed by the Rhizosphere Research Group is enhancing our understanding of the physiology of traits which affect resource capture by crop plants and their genetic control. This will potentially allow us to select crop varieties requiring less fertiliser and irrigation, fulfilling our objective of increasing the economic and environmental sustainability of agricultural enterprises.