Evidence for the derivation of the Drosophila fushi tarazu gene from a Hox gene orthologous to lophotrochozoan Lox5.
The DNA-binding homeobox motif was first identified in several Drosophila homeotic genes but also in fushi tarazu, a gene found in the Hox cluster yet involved in segmentation, not anteroposterior patterning [1]. Homeotic transformations are not seen in insect ftz mutants, and insect ftz genes do not have Hox-like expression except within the nervous system [2] [3]. Insect ftz homeobox sequences link them to the Antp-class genes and Tribolium and Schistocerca orthologs have Antp-class YPWM motifs amino-terminal to the homeobox [2] [3]. Orthologs of ftz cloned from a centipede and an onychophoran [4] show that it predates the emergence of the arthropods, but the inability to pinpoint non-arthropodan orthologs suggested that ftz is the product of a Hox gene duplication in the arthropod ancestor [4] [5]. I have cloned ftz orthologs from a mite and a tardigrade, arthropod outgroups of the insects [6]. Mite ftz is expressed in a Hox-like pattern, confirming its ancestral role in anteroposterior patterning. Phylogenetic analyses indicate that arthropod ftz genes are orthologous to the Lox5 genes of lophotrochozoans (a group that includes molluscs) [7] and, possibly, with the Mab-5 genes of nematodes and Hox6 genes of deuterostomes and would therefore have been present in the triploblast ancestor.
Telford
M J
MJ
Department of Zoology, The Natural History Museum, London, SW7 5BD, UK. M.Telford@nhm.ac.uk
D000595:Amino Acid Sequence; D000818:Animals; D000845:Annelida / Q000235:genetics; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D015870:Gene Expression; D018398:Homeodomain Proteins / Q000145:classification / Q000235:genetics*; D008925:Mites / Q000235:genetics; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid
D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C497169:ftz protein, Drosophila