Lemon encodes an unusual receptor protein-tyrosine kinase expressed during gametogenesis in Hydra.
In a screen for receptor protein-tyrosine kinase (RTK) genes expressed during gametogenesis in the cnidarian Hydra vulgaris, we isolated a cDNA encoding Lemon, an RTK with unusual features. Lemon is orthologous to Drosophila Dtrk, chicken Klg, and human colon carcinoma kinase-4. These genes constitute an RTK class characterized by a conserved transmembrane sequence, the presence of extracellular immunoglobulin-like repeats, and the absence of the DFG motif in the kinase domain. We provide evidence that Lemon is a component of an unusual RTK signal transduction mechanism that may involve transmembrane domain-mediated interactions and may not be dependent on its own catalytic activity. Lemon transcription is dynamically regulated in interstitial cells during asexual budding and gametogenesis. Transcriptional up-regulation occurs early in spermatogenesis and oogenesis concurrent with the local accumulation of interstitial cells in the body column of sexual polyps.
Miller
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Department of Biological Chemistry and the Developmental Biology Center, University of California at Irvine, 92697, USA.
Steele
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D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000378:metabolism; D005718:Gametogenesis; D006801:Humans; D006829:Hydra / Q000196:embryology*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D005656:Fungal Proteins; D008565:Membrane Proteins; D020794:Receptor Protein-Tyrosine Kinases; C413167:lemon protein, Hydra vulgaris