Abstract
Phytohormone, ethylene plays an important role in plant growth and development including fruit ripening and flower senescence. The synthesis of 1-aminocylo-propane-1- carboxylate (ACC), the immediate precursor of ethylene, from S-adenosyl-methionine is catalyzed by ACC synthase; and which is also a rate limiting step in the ethylene biosynthetic pathway. Therefore, it plays a key role in ethylene biosynthesis and the genes that code for ACC synthase are of special interest. Moreover, in zonal geraniums, ethylene bursts released from cuttings can have profound impact on the viability of explants for plant propagation. Biotechnological approach involving genetic modification that may reduce ethylene levels has potential for increasing the shelf-life of cuttings for plant propagation. These considerations have led us to clone several cDNA of ACC synthase genes from Pelargonium x hortorum cv. ‘Sincerity’. To transform geranium cells with Agrobacterium tumefaciens an in vitro regeneration system was developed using very young petiole explants. An Antisense construct of ACC synthase cDNA (PHSacc41) ligated into binary vector pAM696 was introduced into A. tumefaciens EHA 105 cells. Petiole explants were incubated with the Agrobacterium for 15 min and then co-cultivated for several days on MS medium containing 5 mM BAP and 1 mM IAA in the dark without the antibiotics. Selection for transformants was carried out in the presence of kanamycin and timentin. Transgenic plantlets generated were examined for inserted gene cassette by PCR and Southern blotting. Recovery of positive transformants that survived selection suggested that it is possible to transform and introduce genes via transformation in hybrid geraniums for genetic modification.
Highlights
Pelargonium sp., popularly known as geraniums are grown for their colorful flowers and to a limited extent for their scented foliage
The synthesis of 1-aminocylo-propane-1- carboxylate (ACC), the immediate precursor of ethylene, from S-adenosyl-methionine is catalyzed by ACC synthase; and which is a rate limiting step in the ethylene biosynthetic pathway. It plays a key role in ethylene biosynthesis and the genes that code for ACC synthase are of special interest
In the present investigation we have attempted to develop an Agrobacterium tumefaciens based transformation system in the vegetatively propagated geranium with an anti-1-aminocyclopropane-1-carboxylate (ACC) synthase cDNA construct in a Agrobacterium binary vector [11,12] using a plant regeneration system developed for vegetatively propagated geraniums
Summary
Pelargonium sp., popularly known as geraniums are grown for their colorful flowers and to a limited extent for their scented foliage They are important ornamental plants that are widely grown in North America and Europe [1,2,3]. That ACC synthase catalyses the rate limiting step in the ethylene biosynthetic pathway [6] and modulation of this step may result in regulation of ethylene biosynthesis. These considerations had previously led us to the cloning of several cDNA of ACC synthase genes from P x hortorum cv. Results from the present studies show that transformants which survived kanamycin selection show integration of NPT II gene in transgenic plants both by PCR analysis and by southern hybridization
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