Expression of AtECA3 in tobacco modifies its responses to manganese, zinc and calcium

Mn- and Zn-deficiency or excess reduce plant growth and development. Engineering plants with enhanced metal tolerance and accumulation is a major goal in phytoremediation/phytostabilization. Moreover, improved growth under unfavourable mineral conditions contributes to better crop production. In this study, ECA3 cDNA from Arabidopsis thaliana, encoding a P2A-ATPase, was introduced into Nicotiana tabacum var. Xanthi, to examine its value for modifying responses to cations, primarily Mn, Zn and Ca. AtECA3 was ectopically expressed under the CaMV 35S promoter. Transgenic and wild-type plants were tested under hydroponic conditions for their responses to a range of metal exposures (low, moderate and high concentrations), and their tolerance and accumulation were evaluated. AtECA3 expression resulted in better growth of plants at moderate levels of Mn (2 μM) in the medium and enhanced tolerance to high Mn (100 μM). Transgenic plants were also more tolerant to Ca-deficiency conditions, although they showed no differences to wild-type with respect to overall Ca levels. Transgene expression did not produce one unique pattern of Mn and Zn accumulation but instead depended on the external concentration of the particular metal supplied. Thus the enhancement of plant productivity at moderate Mn levels and increased Mn tolerance at high (toxic) Mn supply, as well as the slight increase in Ca-deficiency tolerance seen in ECA3-transformed plants indicates that this gene could be useful in plant biotechnological strategies.

► Ectopic expression of AtECA3: improved Mn-efficiency on moderate Mn (2 μM); increased tolerance to excess of Mn (100 μM); increased tolerance to Ca-deficiency.
► Modification of Zn and Mn accumulation depended on the external metal level.