Pannier is a transcriptional target and partner of tinman during Drosophila cardiogenesis

During Drosophila embryogenesis, the homeobox gene tinman is expressed in t he dorsal mesoderm where it functions in the specification of precursor cel ls of the heart, visceral, and dorsal body wall muscles. The GATA factor ge ne pannier is similarly expressed in the dorsal-most part of the mesoderm w here it is required for the formation of the cardial cell lineage. Despite these overlapping expression and functional properties, potential genetic a nd molecular interactions between the two genes remain largely unexplored. Here, we show that pannier is a direct transcriptional target of Tinman in the heart-forming region. The resulting coexpression of the two factors all ows them to function combinatorially in the regulation of cardiac gene expr ession, and a physical interaction of the proteins has been demonstrated in cultured cells. We also define functional domains of Tinman and Pannier th at are required for their synergistic activation of the D-mef2 differentiat ion gene in vivo. Together, these results provide important insights into t he genetic mechanisms controlling heart formation in the Drosophila model s ystem. (C) 2001 Academic Press.