Identification and Expression Profiling Analysis of the Cation/Ca Exchanger (CCX) Gene Family: Overexpression of SlCCX1-LIKE Regulates the Leaf Senescence in Tomato Flowering Phase.

Cation gradients in plant cellular compartments are maintained by the synergistic actions of various ion exchangers, pumps, and channels. Cation/Ca exchanger (CCX) is one of the clades of the Ca/cation antiporter super family. Here, five genes were identified in tomato. Sequence analysis indicated that SlCCXs have the conserved motifs as the CCX domain. Analysis of the expression level of each member of tomato CCX gene family under cation (Mg, Mn, Na, and Ca) treatment was determined by qRT-PCR. Tomato CCX demonstrated different degrees of responding to cation treatment. Changes in expression was induced by Mg and Mn treatment. Analysis of the expression of genes in different tissues demonstrated that constitutive high expression of a few genes, including and , indicated their role in tomato organ growth and development. Overexpression of dramatically induced leaf senescence. Transcriptome analysis showed that genes related to ROS and several IAA signaling pathways were significantly downregulated, whereas ETH and ABA signaling pathway-related genes were upregulated in overexpression of () plants, compared with the wild type (WT). Moreover, overexpression of plants accumulated more ROS content but less Mg content. Collectively, the findings of this study provide insights into the base mechanism through which CCXs regulate leaf senescence in tomato.