Abstract
BackgroundDAYSLEEPER is a domesticated transposase that is essential for development in Arabidopsis thaliana [Nature, 436:282–284, 2005]. It is derived from a hAT-superfamily transposon and contains many of the features found in the coding sequence of these elements [Nature, 436:282–284, 2005, Genetics, 158:949–957, 2001]. This work sheds light on the expression of this gene and localization of its product in protoplasts and in planta. Using deletion constructs, important domains in the protein were identified.ResultsDAYSLEEPER is predominantly expressed in meristems, developing flowers and siliques. The protein is mainly localized in the nucleus, but can also be seen in discrete foci in the cytoplasm. Using several vesicular markers, we found that these foci belong to vesicular structures of the trans-golgi network, multivesicular bodies (MVB’s) and late endosomes. The central region as well as both the N- and the C-terminus are essential to DAYSLEEPER function, since versions of DAYSLEEPER deleted for these regions are not able to complement the daysleeper phenotype. Like hAT-transposases, we show that DAYSLEEPER has a functionally conserved dimerization domain [J Biol Chem, 282:7563–7575, 2007].ConclusionsDAYSLEEPER has retained the global structure of hAT transposases and it seems that most of these conserved features are essential to DAYSLEEPER’s cellular function. Although structurally similar, DAYSLEEPER seems to have broadened its range of action beyond the nucleus in comparison to transposases.
Highlights
DAYSLEEPER is a domesticated transposase that is essential for development in Arabidopsis thaliana [Nature, 436:282–284, 2005]
Analysis of plant lines containing a 3.6 kb stretch of DNA directly upstream of the DAYSLEEPER start codon, including the 5′ UTR, fused to a mGFP5:gusA gene-construct, showed that the DAYSLEEPER promoter was most active in the root apical meristem, secondary root meristems and the root central stele (Figure 2A-E)
We propose that DAYSLEEPER-fusion proteins accumulate in larger vesicular structures, which are most likely multi-vesicular bodies (MVBs) (Figure 4)
Summary
DAYSLEEPER is a domesticated transposase that is essential for development in Arabidopsis thaliana [Nature, 436:282–284, 2005] It is derived from a hAT-superfamily transposon and contains many of the features found in the coding sequence of these elements [Nature, 436:282–284, 2005, Genetics, 158:949–957, 2001]. After being discovered by Barbara McClintock in the 1940’s, transposable elements (TE’s) were long viewed as integral constituents of the so-called “junk-DNA” [1] These genomic regions were generally considered to represent non-coding, non-functional sequences. A good example of molecular domestication of a transposase gene concerns the FAR1/FHY3 gene-family This acids essential for mobility [8,9]. DAYSLEEPER-like genes have been identified in various species, ranging from basal angiosperms to dicotyledonous species These so-called SLEEPER-genes possess three conserved SLEEPERmotifs, of which the third overlaps largely with hAT block E [9]
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