title: The gap gene giant of Rhodnius prolixus is maternally expressed and required for proper head and abdomen formation.
abstract: The segmentation process in insects depends on a hierarchical cascade of gene activity. The first effectors downstream of the maternal activation are the gap genes, which divide the embryo in broad fields. We discovered a sequence corresponding to the leucine-zipper domain of the orthologue of the gene giant (Rp-gt) in traces from the genome of Rhodnius prolixus, a hemipteran with intermediate germ-band development. We cloned the Rp-gt gene from a normalized cDNA library and characterized its expression and function. Bioinformatic analysis of 12.5 kbp of genomic sequence containing the Rp-gt transcriptional unit shows a cluster of bona fide regulatory binding sites, which is similar in location and structure to the predicted posterior expression domain of the Drosophila orthologue. Rp-gt is expressed in ovaries and maternally supplied in the early embryo. The maternal contribution forms a gradient of scattered patches of mRNA in the preblastoderm embryo. Zygotic Rp-gt is expressed in two domains that after germ band extension are restricted to the head and the posterior growth zone. Parental RNAi shows that Rp-gt is required for proper head and abdomen formation. The head lacks mandibulary and maxillary appendages and shows reduced clypeus-labrum, while the abdomen lacks anterior segments. We conclude that Rp-gt is a gap gene on the head and abdomen and, in addition, has a function in patterning the anterior head capsule suggesting that the function of gt in hemipterans is more similar to dipterans than expected.
authors.affiliation: Laboratorio de Genética y Genómica Funcional, Centro Regional de Estudios Genómicos, Universidad Nacional de La Plata, Florencio Varela, Argentina.
authors.forename: Andrés
authors.initials: A
authors.lastname: Lavore
authors.forename: Lucía
authors.initials: L
authors.lastname: Pagola
authors.forename: Natalia
authors.initials: N
authors.lastname: Esponda-Behrens
authors.forename: Rolando
authors.initials: R
authors.lastname: Rivera-Pomar
mesh_terms: D000005:Abdomen / Q000196:embryology*; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D003001:Cloning, Molecular; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D015723:Gene Library; D006257:Head / Q000196:embryology*; D017403:In Situ Hybridization; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010053:Ovary / Q000378:metabolism; D010802:Phylogeny; D034622:RNA Interference; D023121:RNA, Messenger, Stored / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics; D012239:Rhodnius / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D029721:Drosophila Proteins; D023121:RNA, Messenger, Stored; D012097:Repressor Proteins; C118475:gt protein, Drosophila