Abstract
A model legume Lotus japonicus has been utilized for transgenic studies. The 35S promoter has been widely used in plant transformation systems, but it is suggested that its activity is relatively low in L. japonicus. To search for a new promoter, we have isolated polyubiquitin gene (LjUBQ) from L. japonicus, containing an intron immediate upstream of the initiation codon. Because it was known that an intron enhanced the polyubiquitin gene expression in Arabidopsis thaliana, chimeric genes containing 5'-upstream region including the intron of LjUBQ and the β-glucronidase (GUS) coding region were constructed. In the case of Agrobacterium rhizogenes-mediated transformation, the GUS activity under the LjUBQ promoter was two-fold greater than those under the 35S promoter. In Agrobacterium tumefaiens-mediated transformation, LjUBQ promoter showed higher activity in shoot and root, in comparison with the 35S promoter. These results indicate that the LjUBQ promoter is suitable for constitutive gene expression.
