Co-suppression of the <Emphasis Type="Italic">EIN2</Emphasis>-homology gene <Emphasis Type="Italic">LeEIN2</Emphasis> inhibits fruit ripening and reduces ethylene sensitivity in tomato

EIN2 (ethylene insensitive 2) is a very important component in the ethylene signal transduction pathway. Recently, the genomic DNA and full-length cDNA of LeEIN2 (tomato EIN2) have been isolated in our laboratory. To reveal the function of LeEIN2, transgenic tomato plants with reduced expression levels of LeEIN2 were produced. The fruit ripening and expressions of ripening-related genes encoding polygalacturonase and TomLoxB were inhibited in the LeEIN2-silenced transgenic plants compared to the wild-type Ailsa Craig. In the seedling ethylene response assay, the transgenic tomato plants with reduced LeEIN2 expression exhibited ethylene insensitivity. These results indicate that LeEIN2 plays a critical role in regulating tomato fruit ripening and is a positive regulator in ethylene signal transduction pathway.