Modest calcium increase in tomatoes expressing a variant of Arabidopsis cation/ antiporter

The over-expression of Arabidopsis CAX1 and CAX2 causes transgenic tomato plants to reveal severe $Ca^{2+}$ deficiency-like symptoms such as tip-burn and/or blossom end rot, despite there being sufficient $Ca^{2+}$ in each plant part. To correct the symptoms and to moderately enhance the calcium level, a worldwide vegetable tomato was genetically engineered using a modified Arabidopsis cation/$H^+$ antiporter sCAX2A, a mutant form of Arabidopsis CAX2. Compared with the wild-type, the sCAX2A-expressing tomato plants demonstrated elevated $Ca^{2+}$ levels in the fruits with almost no changes in the levels of $Mn^{2+}$, $Cu^{2+}$, and $Fe^{2+}$. Moreover, expression of sCAX2A in tomato plants did not show any significant alterations in their morphological phenotypes. Unlike 35S::sCAX1 construct, sCAX2A antiporter gene driven by 35S promoter can be a valuable tool for enriching $Ca^{2+}$ contents in the tomato fruit without additional accumulation of the undesirable cations.