Overexpression of the tomato glutamate receptor-like genes SlGLR1.1 and SlGLR3.5 hinders Ca²⁺ utilization and promotes hypersensitivity to Na⁺ and K⁺ stresses

Abstract

Thirteen glutamate receptor-like genes have recently been identified in tomato plants; however, their functions have not been fully elucidated. We overexpressed SlGLR1.1 and SlGLR3.5 in Arabidopsis and found that transgenic plants showed symptoms such as curled and deformed leaves, dwarf stature and retarded growth resembling those of Ca²⁺ deficiency. The results revealed that the levels of Ca²⁺ in aerial tissues did not differ between wild-type and transgenic plants, suggesting that overexpression of SlGLR1.1 and SlGLR3.5 did not affect Ca²⁺ uptake. Transgenic lines were hypersensitive to K⁺ and Na⁺ ionic stresses, which was rescued by addition of Ca²⁺ to the growth medium. Ectopic expression of SlGLR1.1 and SlGLR3.5 resulted in reduced efficiency of Ca²⁺ utilization, suggesting that these genes may play a role in calcium assimilation in tomato plants by controlling ionic transport across the membrane.