Enhanced Drought Tolerance Of T₁ Transgenic Tomato With StBADH Gene

Tomato (Solanum lycopersicum L.) is one of the most important economical vegetable crops worldwide. Drought causes adverse effects on the growth, the productivity and quality of tomato plants. Glycine betaine (GB) is a very effective compatible solute that protects plants against the damaging effects of abiotic stresses. Most commercial tomato plants, which are unable to accumulate GB normally, are susceptible to drought stress. A considerable attention has been given to the genetic engineering GB biosynthesis in an attempt to improve abiotic stresses in tomato. Betaine aldehyde dehydrogenase (BADH) is a key enzyme which converts betaine aldehyde to GB. In the present study, the StBADH gene from highly resistant wild eggplant(Solanum torvum Swartz) was transformed into tomato (cv. Jinpeng No.1). Transgenic tomato plants of T1 progeny were exposed to drought stress to assess the resistance.1. The vector pStBADH was successfully transferred into Agrobacterium tumefaciens EHA105. The StBADH gene was transformed into tomato (cv. Jinpeng No.1) by cotyledon explants with Agrobacterium tumefaciens. Finally, we obtained 1 transformant by half-leaf GUS histochemical assay. PCR and southern blot analyses have confirmed that the exogenous genes have been integrated into tomato genome.2. The progenies of transgenic plant were assayed by GUS histochemical analysis. There were 18 T1 transgenic tomato plants showed expression of blue band which also have shown resistance to Basta. PCR detection of StBADH was positive. It confirmed that the foreign StBADH gene has been successfully integrated into the genome of T1 transgenic tomato plants. Transgenic tomato plants showed significantly higher levels of BADH enzyme activity than wild type plants no matter whether the drought stress was present or not.3. The transgenic (TL1) and wild type (WT) plants were treated with drought stress for 15 days. Drought severely affected plant growth and fruiting but the TL1 plants grew more vigorous than WT plants. The TL1 plants exhibited increased O2-producing rate, H2O2 content, malondialdehyde content and relative electrical conductivity and decreased relative water content significantly. However the damage resulted by drought stress was much gentler than that in WT plants. The activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase) and the content of free proline inereased significantly to protect them from damage, furthermore, the values of these in TL1 plants were significantly higher in comparison to those in WT plants. Taken together, these results clearly indicated that the expression of foreign StBADH gene conferred transgenic tomato plants more tolerance to drought stress.