The sweet potato sporamin promoter confers high-level phytase expression and improves organic phosphorus acquisition and tuber yield of transgenic potato.
The sweet potato sporamin promoter was used to control the expression in transgenic potato of the E. coli appA gene, which encodes a bifunctional enzyme exhibiting both acid phosphatase and phytase activities. The sporamin promoter was highly active in leaves, stems and different size tubers of transgenic potato, with levels of phytase expression ranging from 3.8 to 7.4% of total soluble proteins. Phytase expression levels in transgenic potato tubers were stable over several cycles of propagation. Field tests showed that tuber size, number and yield increased in transgenic potato. Improved phosphorus (P) acquisition when phytate was provided as a sole P source and enhanced microtuber formation in cultured transgenic potato seedlings when phytate was provided as an additional P source were observed, which may account for the increase in leaf chloroplast accumulation (important for photosynthesis) and tuber yield of field-grown transgenic potato supplemented with organic fertilizers. Animal feeding tests indicated that the potato-produced phytase supplement was as effective as a commercially available microbial phytase in increasing the availability of phytate-P to weanling pigs. This study demonstrates that the sporamin promoter can effectively direct high-level recombinant protein expression in potato tubers. Moreover, overexpression of phytase in transgenic potato not only offers an ideal feed additive for improving phytate-P digestibility in monogastric animals but also improves tuber yield, enhances P acquisition from organic fertilizers, and has a potential for phytoremediation.
Hong
Ya-Fang
YF
Graduate Institute of Life Sciences, National Defence University, Neihu, Taipei, Taiwan, ROC.
Liu
Chang-Yeu
CY
Cheng
Kuo-Joan
KJ
Hour
Ai-Ling
AL
Chan
Min-Tsair
MT
Tseng
Tung-Hai
TH
Chen
Kai-Yi
KY
Shaw
Jei-Fu
JF
Yu
Su-May
SM
D010832:6-Phytase / Q000235:genetics* / Q000493:pharmacokinetics; D000818:Animals; D001483:Base Sequence; D001682:Biological Availability; D017931:DNA Primers; D027723:Ipomoea batatas / Q000201:enzymology / Q000235:genetics*; D010758:Phosphorus / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011198:Solanum tuberosum / Q000235:genetics*; D013552:Swine
D017931:DNA Primers; D010940:Plant Proteins; C067142:sporamin protein, Ipomoea batatas; D010758:Phosphorus; D010832:6-Phytase