Simultaneous expression of serine acetyltransferase and cysteine synthase results in enhanced sulfate uptake and increased biomass in Ipomaea aquatica
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The long range goal of the present study is to practically utilize <i>Ipomoea aquatica</i> (water spinach) for phytoremediation of polluted water with sulfuric compounds. In higher plants, the sulfate assimilation pathway consists of 5 key enzymes, among which serine acetyltransferase (SAT) and cysteine synthase (CS) constitute one of the rate limiting steps. Subsequently we have attempted to improve the sulfur assimilation capacity of <i>I. aquatica</i> using genes encoding these two enzymes. Cotyledon segments of seedlings were transformed with <i>Arabidopsis</i> <i>SAT</i> and rice <i>CS</i> genes under the control of the cauliflower mosaic virus 35<i>S</i> promoter. Among 3,245 cotyledon explants, 325 regenerated shoots, and two showed a high tolerance to hygromycin, designated as SR3 and SR10. In transgenic lines, the SAT activity was over 2-fold, and the CS was 3-fold higher than those in the wild type control. The cysteine and glutathione contents were also 6- and 2-fold higher than the control, respectively. When cultured in the presence of 1 g l<sup>−1</sup> (7 mM) sulfate, they accumulated sulfate as much as 20 mg g<sup>−1</sup> fresh weight, being 5-fold higher than the control. Under standard culture conditions, transgenic lines grew faster than the control, showing a 20% increase in fresh weight within 5 weeks cultivation. These results suggested that strengthening of SAT and CS resulted in increase not only in sulfate uptake, but also in total biomass.
- Plant tissue culture letters
Plant tissue culture letters 23(2), 185-189, 2006-03-01
Japanese Society for Plant Cell and Molecular Biology