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Overexpression of the transporters AtZIP1 and AtMTP1 in cassava changes zinc accumulation and partitioning.

Gaitán-Solís E, Taylor NJ, Siritunga D, Stevens W, Schachtman DP - Front Plant Sci (2015)

Bottom Line: Eighteen transgenic events from four constructs, out of a total of 73 events generated, showed significantly higher zinc concentrations in the edible portion of the storage root compared to the non-transgenic controls.The zinc content in the transgenic lines ranged from 4 to 73 mg/kg dry weight (DW) as compared to the non-transgenic control which contained 8 mg/kg.Striking changes in whole plant phenotype such as smaller plant size and chlorotic leaves were observed in transgenic lines that over accumulated zinc.

View Article: PubMed Central - PubMed

Affiliation: Donald Danforth Plant Science Center, St Louis, MO USA.

ABSTRACT
Zinc deficiency in humans is a serious problem worldwide with an estimated one third of populations at risk for insufficient zinc in diet, which leads to impairment of cognitive abilities and immune system function. The goal of this research was to increase the bioavailable zinc in the edible portion of cassava roots to improve the overall zinc nutrition of populations that rely on cassava as a dietary staple. To increase zinc concentrations, two Arabidopsis thaliana genes coding for ZIP1 and MTP1 were overexpressed with a tuber-specific or constitutive promoter. Eighteen transgenic events from four constructs, out of a total of 73 events generated, showed significantly higher zinc concentrations in the edible portion of the storage root compared to the non-transgenic controls. The zinc content in the transgenic lines ranged from 4 to 73 mg/kg dry weight (DW) as compared to the non-transgenic control which contained 8 mg/kg. Striking changes in whole plant phenotype such as smaller plant size and chlorotic leaves were observed in transgenic lines that over accumulated zinc. In a confined field trial five transgenic events grown for 12 months showed a range of zinc concentrations from 18 to 217 mg/kg DW. Although the overexpression of zinc transporters was successful in increasing the zinc concentrations in 25% of the transgenic lines generated, it also resulted in a decrease in plant and tuber size and overall yield due to what appears to be zinc deficiency in the aerial parts of the plant.

No MeSH data available.


Related in: MedlinePlus

Zinc concentration (A–C) and percentage increase in zinc concentration with respect to wild type (D–F) in 4-months-old cassava transgenic storage roots from growth chamber grown plants. Values are mean zinc content normalized for dry weight (DW) of three independent samples, error bars indicate SD. Comparison is between wild type and transgenic events and indicate the different levels of statistical signficance ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001. FZIP denotes FMV:ZIP1 lines, PZIP denotes PAT:ZIP1 lines.
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Figure 1: Zinc concentration (A–C) and percentage increase in zinc concentration with respect to wild type (D–F) in 4-months-old cassava transgenic storage roots from growth chamber grown plants. Values are mean zinc content normalized for dry weight (DW) of three independent samples, error bars indicate SD. Comparison is between wild type and transgenic events and indicate the different levels of statistical signficance ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001. FZIP denotes FMV:ZIP1 lines, PZIP denotes PAT:ZIP1 lines.

Mentions: Eighteen lines consisting of six PAT:AtZIP1, five PAT:AtMTP1, and seven FMV:AtZIP1 (Figure 1), showed significantly higher zinc concentrations in their storage root parenchyma tissue compared to the non-transgenic controls (Figures 1A–C). None of the transgenic events of FMV:AtMTP1 showed a statistically significant increase in zinc concentration in the storage root as compared to controls (Table 1). Both transgenes were capable of driving increased accumulation of Zn in storage parenchyma but promoter choices were critical for the AtMTP1. AtZIP1 under control of the patatin promoter resulted in higher maximum zinc levels, reaching almost six hundred percent (Figure 1F) higher than the controls, compared to only a 400% increase in plants expressing AtMTP1 under the control of the same promoter (Figure 1E). The highest zinc accumulation was detected in storage roots of events overexpressing AtZIP1 under control of the constitutive FMV promoter, in which concentrations reached 75 ppm, an 800–900% increase compared to the non-transgenic controls (Figures 1B,E). No significant increase in zinc accumulation was detected in any of the four transgenic plants containing the two gene construct FMV:AtZIP1- PAT:AtMTP1 (Table 1).


Overexpression of the transporters AtZIP1 and AtMTP1 in cassava changes zinc accumulation and partitioning.

Gaitán-Solís E, Taylor NJ, Siritunga D, Stevens W, Schachtman DP - Front Plant Sci (2015)

Zinc concentration (A–C) and percentage increase in zinc concentration with respect to wild type (D–F) in 4-months-old cassava transgenic storage roots from growth chamber grown plants. Values are mean zinc content normalized for dry weight (DW) of three independent samples, error bars indicate SD. Comparison is between wild type and transgenic events and indicate the different levels of statistical signficance ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001. FZIP denotes FMV:ZIP1 lines, PZIP denotes PAT:ZIP1 lines.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4496839&req=5

Figure 1: Zinc concentration (A–C) and percentage increase in zinc concentration with respect to wild type (D–F) in 4-months-old cassava transgenic storage roots from growth chamber grown plants. Values are mean zinc content normalized for dry weight (DW) of three independent samples, error bars indicate SD. Comparison is between wild type and transgenic events and indicate the different levels of statistical signficance ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001. FZIP denotes FMV:ZIP1 lines, PZIP denotes PAT:ZIP1 lines.
Mentions: Eighteen lines consisting of six PAT:AtZIP1, five PAT:AtMTP1, and seven FMV:AtZIP1 (Figure 1), showed significantly higher zinc concentrations in their storage root parenchyma tissue compared to the non-transgenic controls (Figures 1A–C). None of the transgenic events of FMV:AtMTP1 showed a statistically significant increase in zinc concentration in the storage root as compared to controls (Table 1). Both transgenes were capable of driving increased accumulation of Zn in storage parenchyma but promoter choices were critical for the AtMTP1. AtZIP1 under control of the patatin promoter resulted in higher maximum zinc levels, reaching almost six hundred percent (Figure 1F) higher than the controls, compared to only a 400% increase in plants expressing AtMTP1 under the control of the same promoter (Figure 1E). The highest zinc accumulation was detected in storage roots of events overexpressing AtZIP1 under control of the constitutive FMV promoter, in which concentrations reached 75 ppm, an 800–900% increase compared to the non-transgenic controls (Figures 1B,E). No significant increase in zinc accumulation was detected in any of the four transgenic plants containing the two gene construct FMV:AtZIP1- PAT:AtMTP1 (Table 1).

Bottom Line: Eighteen transgenic events from four constructs, out of a total of 73 events generated, showed significantly higher zinc concentrations in the edible portion of the storage root compared to the non-transgenic controls.The zinc content in the transgenic lines ranged from 4 to 73 mg/kg dry weight (DW) as compared to the non-transgenic control which contained 8 mg/kg.Striking changes in whole plant phenotype such as smaller plant size and chlorotic leaves were observed in transgenic lines that over accumulated zinc.

View Article: PubMed Central - PubMed

Affiliation: Donald Danforth Plant Science Center, St Louis, MO USA.

ABSTRACT
Zinc deficiency in humans is a serious problem worldwide with an estimated one third of populations at risk for insufficient zinc in diet, which leads to impairment of cognitive abilities and immune system function. The goal of this research was to increase the bioavailable zinc in the edible portion of cassava roots to improve the overall zinc nutrition of populations that rely on cassava as a dietary staple. To increase zinc concentrations, two Arabidopsis thaliana genes coding for ZIP1 and MTP1 were overexpressed with a tuber-specific or constitutive promoter. Eighteen transgenic events from four constructs, out of a total of 73 events generated, showed significantly higher zinc concentrations in the edible portion of the storage root compared to the non-transgenic controls. The zinc content in the transgenic lines ranged from 4 to 73 mg/kg dry weight (DW) as compared to the non-transgenic control which contained 8 mg/kg. Striking changes in whole plant phenotype such as smaller plant size and chlorotic leaves were observed in transgenic lines that over accumulated zinc. In a confined field trial five transgenic events grown for 12 months showed a range of zinc concentrations from 18 to 217 mg/kg DW. Although the overexpression of zinc transporters was successful in increasing the zinc concentrations in 25% of the transgenic lines generated, it also resulted in a decrease in plant and tuber size and overall yield due to what appears to be zinc deficiency in the aerial parts of the plant.

No MeSH data available.


Related in: MedlinePlus