Developmental expression of Pax1/9 genes in urochordate and hemichordate gills: insight into function and evolution of the pharyngeal epithelium

• DOI: 10.1242/dev.126.11.2539
• Publication Date: 2021-04-23T19:52:47Z
• Authors: Michio Ogasawara; Hiroshi Wada; Heiko Peters; Nori Satoh
• Keywords: Gills; 0301 basic medicine; 0303 health sciences; DNA, Complementary; Base Sequence; Molecular Sequence Data; Gene Expression Regulation, Developmental; Ciona intestinalis; DNA-Binding Proteins; Evolution, Molecular; Alternative Splicing; 03 medical and health sciences; Chordata, Nonvertebrate; Animals; Paired Box Transcription Factors; Pharynx; Amino Acid Sequence; PAX9 Transcription Factor; RNA, Messenger; Cloning, Molecular; Sequence Alignment; In Situ Hybridization; Phylogeny

ABSTRACT The epithelium of the pharynx contributes to formation gills in hemichordates, urochordates, cephalochordates and primitive vertebrates, is therefore a key structure for understanding developmental mechanisms underlying establishment chordate body plans. Pax1- Pax9-related genes encode transcription factors which are expressed pharyngeal region as well vertebrate pouch that forms thymus parathyroid glands. To explore molecular basis occurrence modifications during evolution, we isolated cDNA clones urochordates (HrPax1/9 Halocynthia roretzi CiPax1/9 Ciona intestinalis) hemichordate (PfPax1/9 Ptychodera flava) from gill libraries. Each gene present single copy per haploid genome. All cDNAs typical paired domains octapeptides but not homeodomain, also true other genes. Molecular phylogenetic analysis based on comparison domain amino-acid sequences suggests HrPax1/9, PfPax1/9 belong Pax1/9 subfamily, they descendants precursor Pax1/Pax9. Screening HrPax1/9 yielded six different types transcripts were generated by alternative splicing. Northern blot, RT-PCR/Southern situ hybridization analyses revealed early embryogenesis epithelia differentiating gills, suggesting these gill-specific factors. might provide first genetic corroboration hypotheses organ-level homology unifies cephalochordates.