SR-protein kinases (SRPKs) and their substrates, the serine/arginine-rich pre-mRNA splicing factors (SR proteins), are key components of splicing machinery and are well conserved across phyla. Despite extensive biochemical investigation, the physiological functions of SRPKs remain unclear. In C. elegans , one SRPK gene and six SR protein genes have been reported. Functional analyses by us and other labs utilizing RNAi technique revealed that one member of SR protein family, CeSF2/ASF, is essential for embryogenesis (1,2), while other SR proteins play redundant roles (2,3);
spk-1 is required for early embryogenesis (1,2). However, we have also demonstrated that
spk-1 is required in germline proliferation and gametogenesis utilizing various RNAi protocols (1). Here we report the isolation and analyses of a deletion mutant within the
spk-1 gene.
spk-1 mutants are comparable to Wild-Type in locomotion and body size. However,
spk-1 mutants shows recessive fully penetrated phenotype of sterility in both hermaphrodites and males. In
spk-1 hermaphrodites germlines are underproliferated and lack oogenesis.
spk-1 males have comparable number of germ nuclei in a gonadal arm, suggesting deficiency in sperm maturation. These observations indicate that zygotic expression of
spk-1 is required for germline proliferation in hermaphrodites and maturation in both hermaphrodites and males. In order to analyze the epistasis between germline proliferation deficiency in
spk-1 mutant and ectopic or tumorous proliferation of germline in
gld-2 (
h292) and
gld-1;
gld-2 double mutant, we generated double and triple mutants. Certain population of
gld-2 (
h292);
spk-1 showed ectopic proliferation of germ nuclei in the most proximal region of the gonad, indicating that
gld-2 (
h292) is epistatic. On the other hand,
gld-2 (
q497)
gld-1 (
q485);
spk-1 showed Glp phenotype, indicating that
spk-1 is epistatic. With these characteristics,
spk-1 mutant may serve as a useful tool to analyze the molecular mechanisms in sex-determination, proliferation and maturation of C. elegans germline. 1: Kuroyanagi H, Kimura T, Wada K, Hisamoto N, Matsumoto K, Hagiwara M. SPK-1, a C. elegans SR protein kinase homologue, is essential for embryogenesis and required for germline development. Mech Dev. 2000; 99(1-2): 51-64. 2: Longman D, Johnstone IL, Caceres JF.@ Functional characterization of SR and SR-related genes in Caenorhabditis elegans . EMBO J. 2000; 19(7): 1625-37. 3: Kawano T, Fujita M, Sakamoto H. Unique and redundant functions of SR proteins, a conserved family of splicing factors, in Caenorhabditis elegans development. Mech Dev. 2000; 95(1-2): 67-76.