Differential mercury volatilization by tobacco organs expressing a modified bacterial merA gene

Abstract

Mercury pollution is a major environmental problem accompanying industrial activities. Most of the mercury released ends up and retained in the soil as complexes of the toxic ionic mercury (Hg 2+), which then can be converted by microbes into the even more toxic methylmercury which tends to bioaccumulate. Mercury detoxification of the soil can also occur by microbes converting the ionic mercury into the least toxic metallic mercury (Hg 0 ) form, which then evaporates. The remediation potential of transgenic plants carrying the MerA gene from E. coli encoding mercuric ion reductase could be evaluated.A modified version of the gene, optimized for plant codon preferences (merApe9, Rugh et al. 1996), was introduced into tobacco by Agrobacterium-mediated leaf disk transformation. Transgenic seeds were resistant to HgCl 2 at 50 μM, and some of them (10-20% ) could germinate on media containing as much as 350 μM HgCl 2 , while the control plants were fully inhibited or died on 50 μM HgCl 2. The rate of elemental mercury evolution from Hg 2+ (added as HgCl 2 ) was 5-8 times higher for transgenic plants than the control. Mercury volatilization by isolated organs standardized for fresh weight was higher (up to 5 times) in the roots than in shoots or the leaves. The data suggest that it is the root system of the transgenic plants that volatilizes most of the reduced mercury (Hg 0 ). It also suggests that much of the mercury need not enter the vascular system to be transported to the leaves for volatilization. Transgenic plants with the merApe9 gene may be used to mercury detoxification for environmental improvement in mercury-contaminated regions more efficiently than it had been predicted based on data on volatilization of whole plants via the upper parts only (Rugh et al. 1996).

Phytoremediation of Mercury and Organomercurials in Chloroplast Transgenic Plants: Enhanced Root Uptake, Translocation to Shoots, and Volatilization

“…Higher uptake of Hg by transgenic roots may be the result of enhanced Hg volatilization. This explanation seems to be supported by previous studies that showed volatilization of elemental mercury enhanced by the function of merA in plant roots (31). In this study, tobacco plants (var.…”

Chlorella species as hosts for genetic engineering and expression of heterologous proteins: Progress, challenge and perspective

“…Various studies have also claimed that using engineered Chlorella as a bioreactor for bioremediation is feasible. Mercuric reductase (MerA) mediates the reduction of Hg 2+ to volatile elemental Hg 0 and has been introduced into land plants, such as Arabidopsis , tobacco, and rice for phytoremediation purposes . Huang et al engineered Chlorella sp.…”

Transformasi Genetik Tembakau dengan Gen Cold Shock Protein melalui Perantara Agrobacterium tumefaciens

“…Daun muda (Jones, 1996;Su et al, 2012) dan suspensi sel (An, 1985;Mayo et al, 2006) merupakan eksplan yang telah berhasil diintroduksi gen asing. Keberhasilan transformasi genetik tembakau telah digunakan untuk berbagai tujuan seperti mengungkap regulasi sistem biologi tanaman (Langbecker et al, 2004), bioremediasi untuk merkuri (He et al, 2001), tanaman model untuk pengujian cekaman biotik (Waigman et al, 2000), dan abiotik (Rizhsky et al, 2002).…”