IDENTIFICATION OF NOVEL GENES IN DROSOPHILA REVEALS THE COMPLEX REGULATION OF EARLY GENE ACTIVITY IN THE MESODERM

Two zygotic genes, twist and snail, are indispensable for the correct establishment of the mesoderm primordium in the early Drosophila embry o. They are also needed for morphogenesis and differentiation of the m esoderm, Both genes code for transcription factors with different, alb eit complementary, functions, Therefore, to understand the early devel opment of the mesoderm, it will be necessary to identify and study the genes regulated by twist and snail. We have searched for downstream g enes using a subtractive cDNA library enriched in sequences expressed in the mesoderm, We have isolated sequences that correspond to 13 nove l early mesoderm genes. These novel genes show a variety of expression patterns and also differ in their dependence on twist and snail funct ions, This indicates that the regulation of early gene activity in the mesoderm is more complex than previously thought.