Tag1 is an autonomous transposable element that shows somatic excision in both Arabidopsis and tobacco.

Abstract

Tag1 is a transposable element first identified as an insertion in the CHL1 gene of Arabidopsis. The chl1::Tag1 mutant originated from a plant (ecotype Landsberg erecta) that had been transformed with the maize transposon Activator (Ac), which is distantly related to Tag1. Genomic analysis of untransformed Landsberg erecta plants demonstrated that two identical Tag1 elements are present in the Landsberg erecta genome. To determine what provides transposase function for Tag1 transposition, we examined Tag1 excision in different genetic backgrounds. First, the chl1::Tag1 mutant was backcrossed to untransformed wild-type Arabidopsis plants to remove the Ac element(s) from the genome. F2 progeny that had no Ac elements but still retained Tag1 in the CHL1 gene were identified. Tag1 still excised in these Ac-minus progeny producing CHL1 revertants; therefore, Ac is not required for Tag1 excision. Next, Tag1 was inserted between a cauliflower mosaic virus 35S promoter and a beta-glucuronidase (GUS) marker gene and transformed into tobacco. Transformants showed blue-staining sectors indicative of Tag1 excision. Transgenic tobacco containing a defective Tag1 element, which was constructed in vitro by deleting an internal 1.4-kb EcoRI fragment, did not show blue-staining sectors. We conclude that Tag1 is an autonomous element capable of independent excision. The 35S-GUS::Tag1 construct was then introduced into Arabidopsis. Blue-staining sectors were found in cotyledons, leaves, and roots, showing that Tag1 undergoes somatic excision during vegetative development in its native host.

Transposition-Based Plant Transformation

“…Such elements include Tip100 of common morning glory (Ipomoea purpurea; Ishikawa et al, 2002), Pac1 of pearl millet (Pennisetum glaucum;MacRae et al, 1994), and various elements in sugar cane (Saccharum officinarum;de Araujo et al, 2005). Furthermore, it may be possible to employ other transposable element systems, such as Arabidopsis (Arabidopsis thaliana) Tag1 (Frank et al, 1997) and maize En-Spm (Kumar et al, 2005).…”

Demography and weak selection drive patterns of transposable element diversity in natural populations of Arabidopsis lyrata

“…example, CACTA TEs are active in methylation-deficient mutants of A. thaliana (48), some families of Ac-like elements show evidence of recent activity (47,49), and both SINE-like and Gypsy-like elements have been inferred to be active within A. thaliana's recent past (35,50). In addition, SINE, Ac-like, CACTA, and MITE TEs are presumed to have been active recently because they contain ORFs (19) or vary in location among A. thaliana ecotypes (51).…”

The Transposition Frequency of Tag1 Elements Is Increased in Transgenic Arabidopsis Lines

“…The Landsberg erecta genome carries two copies of Tag1 (Frank et al, 1997). Because Tag1 was absent from the Columbia ecotype, the elements could be mapped using the Landsberg erecta/Columbia RI lines.…”

“…These residues are conserved in the short inverted repeats of the hAT superfamily of transposable elements (Warren et al, 1994). Somatic excision of Tag1 from the 5 Ј untranslated region of a cauliflower mosaic virus 35S promoter fusion driving ␤ -glucuronidase demonstrated that Tag1 is an autonomous element in A. thaliana and tobacco (Frank et al, 1997). Recently, Tag1 has been used to tag a gene involved in organ separation in A. thaliana (Aida et al, 1997).…”

“…Tag1 is present in two copies in the Landsberg erecta genome but is not present in the other commonly used ecotypes, Columbia and Wassilewskija (Ws; Tsay et al, 1993b;Frank et al, 1997). To extend the use of Tag1 for tagging purposes, we have mapped Tag1 elements onto the restriction fragment length polymorphism map and analyzed the distribution of the element in different A. thaliana ecotypes and different Arabidopsis species.…”