Tissue distribution of PEBBLE RNA and Pebble protein during Drosophila embryonic development

pebble il,pbl is required for cytokinesis during postblastoderm mitoses (Hi me, G., Saint, R., 1992. Zygotic expression of the pebble locus is required for cytokinesis during the postblastoderm mitoses of Drosophila. Developme nt 114, 165-171; Lehner, C.F., 1992. The pebble gene is required for cytoki nesis in Drosophila. J. Cell Sci. 103, 1021-1030) and encodes a putative gu anine nucleotide exchange factor (RhoGEF) for Rho1 GTPase (Prokopenko, S.N. , Brumby, A., O'Keefe, L., Prior, L., He, Y., Saint, R., Bellen, H.J., 1999 . A putative exchange factor for Rho1 GTPase is required for initiation of cytokinesis in Drosophila. Genes Dev. 13, 2301-2314). Mutations in pbi resu lt in the absence of a contractile ring leading to a failure of cytokinesis and formation of polyploid multinucleate cells. Analysis of the subcellula r distribution of PBL demonstrated that during mitosis, PBL accumulates at the cleavage furrow at the anaphase to telophase transition when assembly o f a contractile ring is initiated (Prokopenko, S.N., Brumby, A., O'Keefe, L ., Prior, L., He, Y., Saint, R., Bellen, H.J., 1999. A putative exchange fa ctor for Rho 1 GTPase is required for initiation of cytokinesis in Drosophi la. Genes Dev. 13, 2301-2314). In addition, levels of PBL protein cycle dur ing each round of cell division with the highest levels of PBL found in tel ophase and interphase nuclei. Here, we report the expression pattern of pbl during embryonic development. We show that PEBBLE RNA and PBL protein have a similar tissue distribution and are expressed in a highly dynamic patter n throughout embryogenesis. We shuw that PBL is strongly enriched in dividi ng nuclei in syncytial embryos and in pole cells as well as in nuclei of di viding cells in postblastoderm embryos. Our expression data correlate well with the phenotypes observed in pole cells and. particularly, with the abse nce of cytokinesis after cellular blastoderm formation in pbl mutants. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.