Improvement in Cadmium Tolerance of Tomato Seedlings with an Antisense DNA for 1-Aminocyclopropane-1-Carboxylate Synthase

ABSTRACT

Cadmium (Cd) accelerates leaf senescence and causes cell death in plants. However, the role of ethylene in these responses is currently unclear. In the present study, expressing an antisense 1-aminocyclopropane-1-carboxylic acid synthase gene (LeACS2) reduced the LeACS2 message by 89% under Cd stress, which blocked ethylene evolution in tomato (Lycopersicon esculentum). Cadmium-induced cell death was attenuated in LeACS2 antisense plants, which was complemented by pretreatment of ethylene precursor, suggesting ethylene is required for Cd-induced cell death. The function of ethylene in cell death is hydrogen peroxide (H₂O₂)-dependent. Ethylene blocking inhibited Cd-induced H₂O₂ accumulation. Application of H₂O₂-generating Glc/Glc oxidase promoted cell death in wild-type and LeACS2 antisense plants. Cadmium caused loss of chlorophyll and foliar protein, which was retarded in LeACS2 antisense plants. The LeACS2 antisense plants maintained leaf performance, including transpiration and CO₂ assimilate. These results define a regulatory role of ethylene in the regulation of cell death and leaf performance under Cd stress.

Keywords:

• antisense ACC synthase
• cadmium
• cell death
• ethylene
• oxidative burst

ACKNOWLEDGMENTS

The project is supported by China National Foundation project No. 30571296, 30200191 and 30671471.