Characterization and Expression Analysis of the Ca2+/Cation Antiporter Gene Family in Tomatoes

Abstract

The Ca2+/cation antiporter (CaCA) superfamily plays an important role in the regulation of the essential element Ca2+ and cation concentrations. Characterization and expression analyses of CaCA superfamily genes were performed in the tomato (Solanum lycopersicum) as a representative of dicotyledonous plants and fruit crops. Sixteen CaCA candidate genes were found and identified as tomato CaCA, SlCaCA, by a domain search. In a phylogenetic analysis of the SlCaCA superfamily, the 16 genes were classified into SlCAX, SlNCL, SlCCX, and SlMHX families. Among them, Solyc12g011070, belonging to the SlCAX family, had four splice variants, three of which were predicted to be nonfunctional because of a lack of important motifs. EF-hand domains were only found in SlNCL, in addition to consensus Na_Ca_ex domains, and the region containing EF-hand domains was characteristically long in some members of SlNCL. Furthermore, four genes of the SlCCX family were found to be intronless. As for intracellular localization, one SlCCX member was predicted to be localized to the plasma membrane, while other SlCCXs, SlCAXs, and SlMHXs were predicted to be localized to the vacuolar membrane. The expression patterns of SlCaCAs in various organs, including during several developmental stages of fruit, were classified into four groups. Genes involved in each of the SlCAX, SlNCL, and SlCCX gene families were categorized into three or four groups according to expression patterns, suggesting role sharing within each family. The main member in each subfamily and the members with characteristic fruit expression patterns included genes whose expression was regulated by sugar or auxin and that were highly expressed in a line having metabolite-rich fruit.

Cation/Ca2+ Exchanger 1 (MdCCX1), a Plasma Membrane-Localized Na+ Transporter, Enhances Plant Salt Tolerance by Inhibiting Excessive Accumulation of Na+ and Reactive Oxygen Species

“…The CCX proteins belong to the CaCA (Ca 2+ /cation antiporters) superfamily, which is conserved from bacteria to higher plants and animals (Pittman and Hirschi, 2016). Proteins in the CaCA superfamily usually facilitate the Ca 2+ efflux against the concentration gradient across the membrane and promotes an influx of monovalent cations like H + , Na + , or K + in exchange (Amagaya et al, 2019). Based on their function and evolutionary relationships, the CaCA proteins are divided into five different families: YRBG, Na + /Ca 2+ exchanger (NCX), Na + /Ca 2+ , K + exchanger (NCKX), cation/Ca 2+ exchanger (CCX), and H + /cation exchanger (CAX) (Taneja et al, 2016;Amagaya et al, 2019;Mao et al, 2021).…”

“…Proteins in the CaCA superfamily usually facilitate the Ca 2+ efflux against the concentration gradient across the membrane and promotes an influx of monovalent cations like H + , Na + , or K + in exchange (Amagaya et al, 2019). Based on their function and evolutionary relationships, the CaCA proteins are divided into five different families: YRBG, Na + /Ca 2+ exchanger (NCX), Na + /Ca 2+ , K + exchanger (NCKX), cation/Ca 2+ exchanger (CCX), and H + /cation exchanger (CAX) (Taneja et al, 2016;Amagaya et al, 2019;Mao et al, 2021). Although these proteins have a common conserved Na_Ca_ex structural domain (PF01699), diverse structural and functional characteristics differentiate them from one another.…”

Physiological Characterization of Tomato Introgression Line IL5-4 That Increases Brix and Blossom-end Rot in Ripening Fruit

“…In addition, more detailed physiological study is also of interest. In IL8-3 fruit, which shows high Brix value and low BER incidence, the expression of Ca transport genes is enhanced and some of these gene expressions are induced by sugar (Amagaya et al, 2020;Ikeda et al, 2017). Therefore, further studies on the mechanisms leading to high Brix value and BER incidence in IL5-4 may reveal new insights into sugar metabolism and BER incidence in fruit crops.…”

Redefining the N-Terminal Regulatory Region of the Ca2+/H+ Antiporter CAX1 in Tomato

“…Five additional AtCAXs have been cloned from Arabidopsis ( Shigaki et al, 2006 ). CAXs from other plant species have been intensively studied and the substrate range of these CAXs extends beyond Ca 2+ ( Kamiya et al, 2006 ; Pittman and Hirschi, 2016 ; Amagaya et al, 2020 ).…”

“…In tomato, 100% of AtCAX1 Δ36 -expressing plants exhibited blossom-end rot due to perturbation of calcium partitioning in plant cells ( Park et al, 2005a ; De Freitas et al, 2011 , 2012 ). Although bioinformatics analysis has been performed for tomato SlCAX genes ( Amagaya et al, 2020 ), their functions in Ca 2+ homeostasis and their roles in controlling calcium-related physiological disorders remain to be addressed.…”