Evaluation of salt tolerance in ectoine-transgenic tomato plants (Lycopersicon esculentum) in terms of photosynthesis, osmotic adjustment, and carbon partitioning

Ectoine is a common compatible solute in halophilic bacteria. Its biosynthesis originates from L-aspartate β-semialdehyde and requires three enzymes: L-2, 4-diaminobutyric acid aminotransferase (gene: ect B), L-2,4-diaminobutyric acid acetyl transferase (gene: ect A) and L-ectoine synthase (gene: ect C). Genetically engineered tomato plants expressing the three H. elongata genes (ectA, ectB, and ectC) generated showed no phenotypic abnormality. Expression of the ectoine biosynthetic genes was detected in the T3 transgenic plants by Northern blot analysis. The ectoine accumulating T3 plants were evaluated for salt tolerance by examining their photosynthestic activity, osmotic adjustment and carbon partitioning. Nuclear magnetic resonance (NMR) detected the accumulation of ectoine. The concentration of ectoine increased with increasing salinity. The transgenic lines showed higher activities of peroxidase, while the malondialdehyde (MDA) concentration was decreased under salinity stress condition. In additio...