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Transgenic expression of phytase and acid phosphatase genes in alfalfa (Medicagosativa) leads to improved phosphate uptake in natural soils.

Ma XF, Tudor S, Butler T, Ge Y, Xi Y, Bouton J, Harrison M, Wang ZY - Mol. Breed. (2011)

Bottom Line: The MtPT1 promoter was more effective than the CaMV35S promoter in regulating gene expression and extracellular secretion under P-deficient conditions.Transgene effects were more obvious in soil with lower pH and lower natural P reserves than in soil with neutral pH and relatively higher P storage.The total P concentration in leaf tissues of the high-expressing transgenic lines was significantly higher than that of the control.

View Article: PubMed Central - PubMed

ABSTRACT
Alfalfa (Medicagosativa L.) is one of the most widely grown crops in the USA. Phosphate (P) deficiency is common in areas where forage crops are grown. To improve the use of organic phosphate by alfalfa, two Medicagotruncatula genes, phytase (MtPHY1) and purple acid phosphatase (MtPAP1), were overexpressed in alfalfa under the control of the constitutive CaMV35S promoter or the root-specific MtPT1 promoter. Root enzyme activity analyses revealed that although both genes lead to similar levels of acid phosphatase activities, overexpression of the MtPHY1 gene usually results in a higher level of phytase activity than overexpression of the MtPAP1 gene. The MtPT1 promoter was more effective than the CaMV35S promoter in regulating gene expression and extracellular secretion under P-deficient conditions. Measurement of growth performance of the transgenic lines further proved that the best promoter-gene combination is the MtPHY1 gene driven by the MtPT1 promoter. Compared to the control, the plants with high levels of transgene expression showed improved growth. The biomass of several transgenic lines was three times that of the control when plants were grown in sand supplied with phytate as the sole P source. When the plants were grown in natural soils without additional P supplement, the best performing transgenic lines produced double the amount of biomass after 12 weeks (two cuts) of growth. Transgene effects were more obvious in soil with lower pH and lower natural P reserves than in soil with neutral pH and relatively higher P storage. The total P concentration in leaf tissues of the high-expressing transgenic lines was significantly higher than that of the control. The transgenes have great potential for improving plant P acquisition and biomass yield in P-deficient agricultural soils. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11032-011-9628-0) contains supplementary material, which is available to authorized users.

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Related in: MedlinePlus

APase activity of transgenic and control (CTL) alfalfa plants. The first letter of each plant name represents the gene construct used for producing the transgenic line. a Activities of whole root extracts of the MtPHY1 plants. b Activities of whole root extracts of the MtPAP1 plants. c Activities of root saps of the MtPHY1 plants. d Activities of root saps of the MtPAP1 plants. e Activity correlation between whole root extracts and root saps of the MtPHY1 plants. f Activity correlation between whole root extracts and root saps of the MtPAP1 plants. Data are presented as means ± SE (n = 6)
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Fig1: APase activity of transgenic and control (CTL) alfalfa plants. The first letter of each plant name represents the gene construct used for producing the transgenic line. a Activities of whole root extracts of the MtPHY1 plants. b Activities of whole root extracts of the MtPAP1 plants. c Activities of root saps of the MtPHY1 plants. d Activities of root saps of the MtPAP1 plants. e Activity correlation between whole root extracts and root saps of the MtPHY1 plants. f Activity correlation between whole root extracts and root saps of the MtPAP1 plants. Data are presented as means ± SE (n = 6)

Mentions: APase catalyzes the breakdown of phosphomonoesters, and thus the APase activity of the extracted enzyme should represent its general ability to degrade most forms of organic phosphate. In the present study, the APase activities were measured using pNPP and the results are plotted in Fig. 1 (for statistical details see Suppl. Table 1). For whole root extract, it is evident that APase activities of almost all transgenic plants (except for B4, C3, C7 and E7) were higher than that of the control, though large variations exist among different transgenic lines (Fig. 1a, b, Suppl. Table 1a). The average transgenic enzyme activity showed an approximately threefold increase and the highest (plant B5 of Fig. 1a) activity was 4.4-fold that of the control. Out of the 60 transgenic plants, 11 (A4, B5, B6, B9, B11, D2, D8, E5, E8, F4 and F8) showed an activity increase of greater than fourfold compared to the control (Fig. 1a, b).Fig. 1


Transgenic expression of phytase and acid phosphatase genes in alfalfa (Medicagosativa) leads to improved phosphate uptake in natural soils.

Ma XF, Tudor S, Butler T, Ge Y, Xi Y, Bouton J, Harrison M, Wang ZY - Mol. Breed. (2011)

APase activity of transgenic and control (CTL) alfalfa plants. The first letter of each plant name represents the gene construct used for producing the transgenic line. a Activities of whole root extracts of the MtPHY1 plants. b Activities of whole root extracts of the MtPAP1 plants. c Activities of root saps of the MtPHY1 plants. d Activities of root saps of the MtPAP1 plants. e Activity correlation between whole root extracts and root saps of the MtPHY1 plants. f Activity correlation between whole root extracts and root saps of the MtPAP1 plants. Data are presented as means ± SE (n = 6)
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Related In: Results  -  Collection

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Fig1: APase activity of transgenic and control (CTL) alfalfa plants. The first letter of each plant name represents the gene construct used for producing the transgenic line. a Activities of whole root extracts of the MtPHY1 plants. b Activities of whole root extracts of the MtPAP1 plants. c Activities of root saps of the MtPHY1 plants. d Activities of root saps of the MtPAP1 plants. e Activity correlation between whole root extracts and root saps of the MtPHY1 plants. f Activity correlation between whole root extracts and root saps of the MtPAP1 plants. Data are presented as means ± SE (n = 6)
Mentions: APase catalyzes the breakdown of phosphomonoesters, and thus the APase activity of the extracted enzyme should represent its general ability to degrade most forms of organic phosphate. In the present study, the APase activities were measured using pNPP and the results are plotted in Fig. 1 (for statistical details see Suppl. Table 1). For whole root extract, it is evident that APase activities of almost all transgenic plants (except for B4, C3, C7 and E7) were higher than that of the control, though large variations exist among different transgenic lines (Fig. 1a, b, Suppl. Table 1a). The average transgenic enzyme activity showed an approximately threefold increase and the highest (plant B5 of Fig. 1a) activity was 4.4-fold that of the control. Out of the 60 transgenic plants, 11 (A4, B5, B6, B9, B11, D2, D8, E5, E8, F4 and F8) showed an activity increase of greater than fourfold compared to the control (Fig. 1a, b).Fig. 1

Bottom Line: The MtPT1 promoter was more effective than the CaMV35S promoter in regulating gene expression and extracellular secretion under P-deficient conditions.Transgene effects were more obvious in soil with lower pH and lower natural P reserves than in soil with neutral pH and relatively higher P storage.The total P concentration in leaf tissues of the high-expressing transgenic lines was significantly higher than that of the control.

View Article: PubMed Central - PubMed

ABSTRACT
Alfalfa (Medicagosativa L.) is one of the most widely grown crops in the USA. Phosphate (P) deficiency is common in areas where forage crops are grown. To improve the use of organic phosphate by alfalfa, two Medicagotruncatula genes, phytase (MtPHY1) and purple acid phosphatase (MtPAP1), were overexpressed in alfalfa under the control of the constitutive CaMV35S promoter or the root-specific MtPT1 promoter. Root enzyme activity analyses revealed that although both genes lead to similar levels of acid phosphatase activities, overexpression of the MtPHY1 gene usually results in a higher level of phytase activity than overexpression of the MtPAP1 gene. The MtPT1 promoter was more effective than the CaMV35S promoter in regulating gene expression and extracellular secretion under P-deficient conditions. Measurement of growth performance of the transgenic lines further proved that the best promoter-gene combination is the MtPHY1 gene driven by the MtPT1 promoter. Compared to the control, the plants with high levels of transgene expression showed improved growth. The biomass of several transgenic lines was three times that of the control when plants were grown in sand supplied with phytate as the sole P source. When the plants were grown in natural soils without additional P supplement, the best performing transgenic lines produced double the amount of biomass after 12 weeks (two cuts) of growth. Transgene effects were more obvious in soil with lower pH and lower natural P reserves than in soil with neutral pH and relatively higher P storage. The total P concentration in leaf tissues of the high-expressing transgenic lines was significantly higher than that of the control. The transgenes have great potential for improving plant P acquisition and biomass yield in P-deficient agricultural soils. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11032-011-9628-0) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus