TRANSFORMATION OF PEAR (PYRUS COMMUNIS CV. 'LA FRANCE') WITH GENES INVOLVED IN ETHYLENE BIOSYNTHESIS

The plant hormone ethylene is known to be important during fruit ripening, especially in typical climacteric fruits, including pear (Pyrus communis L.). It is currently thought that the inhibition of ethylene biosynthesis via genetic engineering should improve the quality and shelf life of fruits. 1-Aminocyclopropane- 1-carboxylate (ACC) synthase and ACC oxidase are two key enzymes in the ethylene biosynthetic pathway. Therefore, inhibiting the expression of genes encoding these two enzymes should reduce ethylene synthesis. We cloned the cDNAs encoding ACC synthase and ACC oxidase from ripe pear (cv. ‘La France’) fruits, designated LF-ACS1 and LF-ACO1, respectively, and introduced them into the ‘La France’ pear in either sense or antisense orientation using Agrobacterium-mediated leaf disc transformation. T-DNA integrations into the pear genome were confirmed by PCR and Southern analysis. In transgenic lines containing sense or antisense LF-ACO1 transgenes, the expression of endogenous ACC oxidase gene was examined by Northern analysis. The results demonstrated that the expression of ACC oxidase was inhibited in nearly all antisense lines and in one sense line. Ethylene production in the presence of ACC, a unique substrate of ACC oxidase, was lower in these transgenic shoots.

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