The SlCBL10 Calcineurin B-Like Protein Ensures Plant Growth under Salt Stress by Regulating Na and Ca Homeostasis.

Characterization of a new tomato () T-DNA mutant allowed for the isolation of the () gene whose lack of function was responsible for the severe alterations observed in the shoot apex and reproductive organs under salinity conditions. Physiological studies proved that gene is required to maintain a proper low Na/Ca ratio in growing tissues allowing tomato growth under salt stress. Expression analysis of the main responsible genes for Na compartmentalization (i.e. , , , [] and V-ATPase []) supported a reduced capacity to accumulate Na in mutant leaves, which resulted in a lower uploading of Na from xylem, allowing the toxic ion to reach apex and flowers. Likewise, the tomato and (), key genes for Ca fluxes to the vacuole, showed abnormal expression in plants indicating an impaired Ca release from vacuole. Additionally, complementation assay revealed that is a true ortholog of the Arabidopsis () gene, supporting that the essential function of CBL10 is conserved in Arabidopsis and tomato. Together, the findings obtained in this study provide new insights into the function of in salt stress tolerance. Thus, it is proposed that SlCBL10 mediates salt tolerance by regulating Na and Ca fluxes in the vacuole, cooperating with the vacuolar cation channel and the two vacuolar H-pumps, and , which in turn are revealed as potential targets of .