Abstract
Genetic modifications of floral organs are important in the breeding of Malus species. Flower-specific promoters can be used to improve floral organs specifically, without affecting vegetative organs, and therefore developing such promoters is highly desirable. Here, we characterized two paralogs of the Arabidopsis thaliana gene AGAMOUS (AG) from Malus domestica (apple): MdAG1 and MdAG2. We then isolated the second-intron sequences for both genes, and created four artificial promoters by fusing each intron sequence to a minimal 35S promoter sequence in both the forward and reverse directions. When transferred into tobacco (Nicotiana benthamiana) by Agrobacterium tumefaciens-mediated stable transformation, one promoter, rMdAG2I, exhibited activity specifically in flowers, whereas the other three also showed detectable activity in vegetative organs. A test of the four promoters’ activities in the ornamental species Malus micromalus by Agrobacterium-mediated transient transformation showed that, as in tobacco, only rMdAG2I exhibited a flower-specific expression pattern. Through particle bombardment transformation, we demonstrated that rMdAG2I also had flower-specific activity in the apple cultivar ‘Golden Delicious’. The flower-specific promoter rMdAG2I, derived from M. domestica, thus has great potential for use in improving the floral characteristics of ornamental plants, especially the Malus species.
Highlights
The genus Malus comprises more than 30 species with both ornamental and edible uses [1]
We reported that the reverse version of the second intron of MdMADS22 drove the flower-specific expression of target genes both in tobacco and in two Malus species, Malus domestica and the ornamental Malus micromalus
We identified two AG paralogs, which we named MdAG1 and MdAG2
Summary
The genus Malus comprises more than 30 species with both ornamental and edible uses [1]. A flower-specific promoter could be of great utility by enabling the application of transgenic methods to improve flower traits, without affecting vegetative growth. We reported that the reverse version of the second intron of MdMADS22 drove the flower-specific expression of target genes both in tobacco and in two Malus species, Malus domestica (apple) and the ornamental Malus micromalus (midget crabapple). This artificial promoter could serve as a tool for the genetic manipulation of Malus species and other flowering plants
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