The expression of VegT requires both Xenopus nodal-related and FGF signaling pathways during early Xenopus embryogenesis

Abstract

Xenopus nodal-related (Xnr) proteins and FGF play crucial roles during mesoderm induction in amphibian Xenopus laevis embryos. The endogenous and ectopic Xnr-induced expression of mesodermal genes, including VegT, requires FGF signaling such that their expression is abolished when FGF signaling is inhibited. However, the molecular mechanism for the interaction between the two signaling pathways is largely unknown. In order to understand their interaction, we isolated a 2.2 kb-long DNA fragment immediately upstream of Xenopus laevis VegT transcription start site and identified a 274 bp-long fragment that requires both Xnr and FGF signaling for transcriptional activation. From this sequence we identified two regulatory elements; one was necessary for Xnr1-induced activation and the other for FGF-induced activation. Our results suggest that the expression of VegT is regulated, at least in part, by two distinct transcription factors which mediate Xnr and FGF signaling, respectively. © The Genetics Society of Korea.