GENETIC-CHARACTERIZATION OF TUBE AND PELLE, GENES REQUIRED FOR SIGNALING BETWEEN TOLL AND DORSAL IN THE SPECIFICATION OF THE DORSAL-VENTRALPATTERN OF THE DROSOPHILA EMBRYO

tube and pelle are two of the maternally transcribed genes required fo r dorsal-ventral patterning of the Drosophila embryo. Females homozygo us for strong alleles of tube or pelle produce embryos that lack all v entral and lateral embryonic pattern elements. By analyzing the phenot ypes caused by 24 pelle and 9 tube alleles, we have defined characteri stic features of the two genes, including the extremely variable pheno types of a number of tube alleles and the antimorphic character of a n umber of pelle alleles. Double mutant females carrying dominant ventra lizing alleles of Toll and dorsalizing alleles of tube or pelle produc e dorsalized embryos, suggesting that tube and pelle act downstream of the membrane protein Toll in the signaling pathway that defines the e mbryonic dorsal-ventral pattern. Both tube and pelle are also importan t zygotically for survival: at least 30% of the zygotes lacking either tube or pelle die before adult stages, while 90-95% of tube- pelle-do uble mutant zygotes die. We discuss the phenotypes of tube-pelle doubl e mutants in the context of whether the two proteins interact directly .