Evolution of Hox-like genes in Cnidaria: Study of Hydra Hox repertoire reveals tailor-made Hox-code for Cnidarians.
Hox and ParaHox genes play decisive roles in patterning the anterior-posterior body axis in Bilateria. Evolutionary origin of Hox genes and primary body axis predate the divergence of Bilateria and Cnidaria. However, function of Cnidarian Hox-like genes and their regulation in axis determination is obscure due to studies limited to a few representative model systems. Present investigation is conducted using Hydra, a Hydrozoan member of phylum Cnidaria, to gain insights into the roles of Cnidarian Hox-like genes in primary axis formation. Here, we report identification of six Hox-like genes from our in-house transcriptome data. Phylogenetic analysis of these genes shows bilaterian counterparts of Hox1, Gsx and Mox. Additionally, we report CnoxB_HVUL, CnoxC2_HVUL and CnoxC3_HVUL belonging to two Cnidarian specific groups. In situ hybridization analysis of Hydra homologues provided important clues about their possible roles in pattern formation of polyps and bud development. Specifically, Hox1_HVUL is regulated by Wnt signaling and plays critical role in head formation. Collating information about expression patterns of different Hox-like genes from previous reports and this study reveals no conformity within Cnidaria. Indicating that unlike in Bilateria, there is no consolidated Hox-code determining primary body axis in Cnidaria.
Indian Institute of Science Education and Research, Pashan, Pune 411008, India.
Puli Chandramouli
PC
Reddy
Indian Institute of Science Education and Research, Pashan, Pune 411008, India.
Manu K
MK
Unni
Indian Institute of Science Education and Research, Pashan, Pune 411008, India.
Akhila
A
Gungi
Indian Institute of Science Education and Research, Pashan, Pune 411008, India.
Pallavi
P
Agarwal
Indian Institute of Science Education and Research, Pashan, Pune 411008, India; National Centre for Cell Science, Ganeshkhind, Pune 411007, India. Electronic address: sanjeev@iiserpune.ac.in.
Sanjeev
S
Galande
D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D003063:Cnidaria / Q000235:genetics*; D019143:Evolution, Molecular; D005801:Genes, Homeobox / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D006829:Hydra / Q000235:genetics*; D010802:Phylogeny
D018398:Homeodomain Proteins
Evolution; Hox; Hydra; Phylogeny and expression pattern