Originally published as Genetics Published Articles Ahead of Print on July 27, 2008.

Genetics, Vol. 179, 1973-1987, August 2008, Copyright © 2008
doi:10.1534/genetics.108.087858

Dissection of Darkener of Apricot Kinase Isoform Functions in Drosophila

Arlette Kpebe and Leonard Rabinow1

Signalisation Développement et Cancer, Université Paris 11, CNRS UMR C8080, 91405 Orsay Cedex, France

1 Corresponding author: Signalisation Développement et Cancer, CNRS UMR C8080, Université Paris 11, Bâtiment 442 bis, 91405 Orsay Cedex, France.
E-mail: leonard.rabinow{at}u-psud.fr

The Darkener of apricot (Doa) locus of Drosophila encodes a LAMMER protein kinase affecting alterative splicing, and hence sex determination, via the phosphorylation of SR and SR-like proteins. Doa encodes 6 different kinases via alternative promoter usage. To provide further insight into the roles of the multiple isoforms, we mapped polymorphisms, deletions, and P-element insertions in the locus, identifying several that are largely, if not completely, isoform specific in their effects. These tests, along with the use of lines permitting overexpression and interfering RNA expression, demonstrate that the major isoforms of 55 and 105 kDa perform separate functions. The 105-kDa and a minor 138-kDa isoform are both vital but do not apparently perform functions essential for sex determination. Curiously, male-specific lethality induced by overexpression of the 55-kDa kinase in the larval fat body is rescued by coexpression of TRA, suggesting a sex-specific physiological role for this isoform. Maternal effects in which the survival of heteroallelic adults depends upon the direction of the cross are consistent with a role for a 105-kDa cytoplasmic kinase in oogenesis or early larval development.