[Phytate-phosphorus uptake and utilization by transgenic tobacco carrying Bacillus subtilis phytase gene]

Phytate is the major form of organic phosphorus in soil. Elevating the phyrase activity in transgenic plants may be an effective approach to promote their phytate-phosphorus utilization, but little is known about the applied conditions. In this study, several transgenic tobacco lines carrying Bacillus subtilis phytase gene were compared with wild-type tobacco, in terms of their ability in acquiring phosphorus from phytate in sterilized agar, sand and soil. In sterilized agar, transgenic tobacco plants were more efficient in phytate-phosphorus uptake and utilization, and their biomass and total phosphorus content were 3.6-10.7 and 2.2-4.6 fold of the wild-type's, respectively. In sand and soil systems, however, there were no significant differences in biomass and total phosphorus content between the trsansgenic and wild-type tobacco plants. These results indicated that Bacillus phytase transgene could only improve the phytate-phosphorus uptake by transgenic plants under sterilized condition, and its effectiveness might be limited under natural conditions because of microbial decomposition and mineral fixation. Therefore, further research is needed to understand the limiting factors on the functions of the transgene.