Ectopic expression of a maize calreticulin mitigates calcium deficiency-like disorders in sCAX1-expressing tobacco and tomato.

Deregulated expression of an Arabidopsis H+/Ca2+ antiporter (sCAX1) in agricultural crops increases total calcium (Ca2+) but may result in yield losses due to Ca2+ deficiency-like symptoms. Here we demonstrate that co-expression of a maize calreticulin (CRT, a Ca2+ binding protein located at endoplasmic reticulum) in sCAX1-expressing tobacco and tomato plants mitigated these adverse effects while maintaining enhanced Ca2+ content. Co-expression of CRT and sCAX1 could alleviate the hypersensitivity to ion imbalance in tobacco plants. Furthermore, blossom-end rot (BER) in tomato may be linked to changes in CAX activity and enhanced CRT expression mitigated BER in sCAX1 expressing lines. These findings suggest that co-expressing Ca2+ transporters and binding proteins at different intracellular compartments can alter the content and distribution of Ca2+ within the plant matrix.