Abstract
IAA19 is an auxin-responsive gene which mediates tropic responses in hypocotyl and lateral root formation (Tatematsu et al., 2004). For further understanding of IAA19 gene expression, 3kbp promoter and two reporter genes (fluorescent protein and beta-glucuronidase) were fused individually, and introduced into Arabidopsis. In a root of transgenic plants, IAA19:reporter expressed in protoxylem, metaxylem, root cap, lateral root cap. Sporadic expression of IAA19:reporter was observed in central stele along with primary root, and some of them were primordia of lateral root. Luciferase was employed as no-invasive reporter (pIAA19:luc). Time-lapse imaging of bioluminescense revealed that pIAA19:luc expressed in prior to the formation of lateral root. On the other hand, asymmetric expression in lateral root cap was observed when root tip was placed in horizontal position. Further incubation of the root reoriented root tip vertical and the asymmetric expression diminished. We will discuss the advantages of bioluminescence imaging for auxin-responsive gene expression.
