Germinal Excision and Reinsertion Frequencies of the Mobile Element Ds Transposed from Two Unlinked T-DNA Loci in Tomato

Acceptor sites of unlinked transposed Ds element from two T-DNA loci in tomato were mapped. Experimental data obtained from TC sub(1) progeny testing were employed for estimation of germinal excision frequency (GEF) of Ds element and frequency of its reinsertion (FR). The donor T-DNAs 1481J and 1601D, containing a 35S:NPT transformation marker, a 35S:BAR or nos:BAR excision marker conferring phosphinothricine resistance and a Ds element in the 5' untranslated leader of the nos (or 35S):BAR gene, were located on chromosome 7 and 8, respectively. Ds transposition was induced by 105121 T-DNA carrying stabilized Ac (sAc) which provides a source of transposase and 2':GUS marker conferring beta -glucuronidase activity. Tomato plants harbouring the Ds in 1481J or 1601D locus and sAc were crossed and F sub(1) seedlings heterozygous for both Ds and sAc were identified. These plants, 72 with Ds in 1481J and 65 with Ds in 1601D, were crossed individually as seed parents to wild-type plants to generate TC sub(1) progenies. TC sub(1) seed was germinated on phosphinothricine (Basta)-containing medium, and individual seedlings carrying a transposed Ds and lacking sAc were identified by PCR (to detect the Ds) on phosphinothricine resistant individuals that lacked beta -glucuronidase activity. From segregation ratio in TC sub(1) the germinal excision and reinsertion frequencies of the Ds element were estimated for individual F sub(1) plants. A total of 14560 TC sub(1) seedlings of 1481J and 16195 TC sub(1) seedlings of 1601D was analyzed. We observed high variation between individual plants as regards both GEF and FR despite of donor locus (1481J or 1601D), however, the average germinal excision frequencies as well as average frequencies of reinsertion were very similar for both donor loci: GEF sub(1481J) = 24 %, GEF sub(1601D) = 25 %, FR sub(1481J) = 42 %, FR sub(1601D) = 46 %.