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Increased metal tolerance and bioaccumulation of zinc and cadmium in Chlamydomonas reinhardtii expressing a AtHMA4 C‐terminal domain protein
Author(s) -
Ibuot Aniefon,
Webster Rachel E.,
Williams Lorraine E.,
Pittman Jon K.
Publication year - 2020
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.27476
Subject(s) - chlamydomonas reinhardtii , biosorption , cadmium , bioremediation , bioaccumulation , metal , zinc , chemistry , environmental chemistry , nuclear chemistry , transgene , biophysics , biochemistry , biology , gene , contamination , adsorption , ecology , organic chemistry , sorption , mutant
The use of microalgal biomass for metal pollutant bioremediation might be improved by genetic engineering to modify the selectivity or capacity of metal biosorption. A plant cadmium (Cd) and zinc (Zn) transporter (AtHMA4) was used as a transgene to increase the ability of Chlamydomonas reinhardtii to tolerate 0.2 mM Cd and 0.3 mM Zn exposure. The transgenic cells showed increased accumulation and internalization of both metals compared to wild‐type. AtHMA4 was expressed either as the full‐length (FL) protein or just the C‐terminal (CT) tail, which is known to have metal‐binding sites. Similar Cd and Zn tolerance and accumulation was observed with expression of either the FL protein or CT domain, suggesting that enhanced metal tolerance was mainly due to increased metal binding rather than metal transport. The effectiveness of the transgenic cells was further examined by immobilization in calcium alginate to generate microalgal beads that could be added to a metal contaminated solution. Immobilization maintained metal tolerance, while AtHMA4‐expressing cells in alginate showed a concentration‐dependent increase in metal biosorption that was significantly greater than alginate beads composed of wild‐type cells. This demonstrates that expressing AtHMA4 FL or CT has great potential as a strategy for bioremediation using microalgal biomass.