Expression and Inheritance of a Transgene for Salinity Tolerance in Tomato

Abstract

The study was conducted to investigate the expression and inheritance of the transgene, oxalate oxidase, conferring salinity tolerance in transgenic lines of tomato (Lycopersicon esculentum Mill.). R₂ seeds from different lines were assessed for oxalate oxidase, and first back-crosses were planted in the glasshouse with two levels of salt treatments (0% and 1.5%) to determine the level of enzyme expression. A qualitative assessment of R₂ seeds for oxalate oxidase revealed that the gene was inherited in a normal Mendelian fashion as a single dominant gene producing a 3:1 ratio (84%) and 16% produced distinct 15:1 ratios indicating the possibility of presence of two copies of the oxalate oxidase gene in the tomato genome. A quantitative assessment of the tomato leaf extract for oxalate oxidase at different growth stages revealed that the enzyme activity was as low as 0.36 nM H₂O₂/min/mg protein in the control genotype to as high as 115 nM H₂O₂/min/mg protein in transgenic lines, but there were no significant differences between transgenic lines. Salt treated plants had higher enzyme activity than untreated. There were no differences between young and old leaves for enzyme expression. There was a decreasing trend of enzyme activity with the age of the plant.

J. Inst. Agric. Anim. Sci. 2003 24:43-50