The Drosophila p38 MAPK pathway is required during oogenesis for egg asymmetric development

The Drosophila p38 MAPK pathway is required during oogenesis for egg asymmetric development

Centre de Biologie du Développement, UMR5547 Centre National de la Recherche Scientifique (CNRS), 31062 Toulouse Cedex, France; Department of Molecular Biology, Graduate School of Science, Nagoya University, and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, Nagoya 464-0814, Japan; Developmental Genetics Programme, Sheffield, South Yorkshire S10 2TN, UK; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115 USA

Abstract

In mammalian cells, the p38 mitogen-activated protein kinase (MAPK) pathway is activated in response to a variety of environmental stresses and inflammatory stimuli. However, the role of p38 MAPK signaling in unchallenged conditions remains largely unknown. We have isolated mutations in a Drosophila p38 MAPKK gene homolog,licorne (lic), and show that during oogenesis,lic is required in the germ line for correct asymmetric development of the egg. In lic mutant egg chambers,oskar mRNA posterior localization is not properly maintained, resulting in anteroposterior patterning defects in the embryo. Furthermore, lic loss-of-function in the germ line leads to reduced EGF receptor activity in dorsal follicle cells and ventralization of the egg shell. Both these defects are associated with a diminution of gurken protein levels in the oocyte. Our phenotypic data argue for a role of lic in a post-transcriptional regulation of the grk gene. Furthermore, they show that in addition to the well-characterized Ras/Raf/ERK MAPK pathway acting in the follicle cells, another related signaling cascade, the p38 MAPK pathway, is required in the germ line for correct axes determination. These results provide the first genetic demonstration of an essential function for a p38 pathway during development.