Developmental Genetics in the Ascidian Ciona intestinalis

Abstract

The ascidian Ciona intestinalis provides an appealingly simple experimental system for the investigation of the molecular mechanisms underlying cell-fate specification during development.The draft genome sequences and a large EST/cDNA databases supports the study of gene functions.However, forward genetics, as exemplified by germline transgenesis and creation of mutants, has not been developed in the marine invertebrates.Our recent research focused on the establishment of such genetic approaches in Ciona.Currently, creation of stable transgenic lines, enhancer trappings and insertional mutagenesis have been successfully introduced in Ciona with Minos transposon. Germline transgenesis of Ciona intestinalis with Minos transposonMinos is a member of Tc1/mariner superfamily transposon derived from an insect, Drosophila hydei.Minos has the high activity for germline transformation in Ciona intestinalis.When Minos transposon DNA is introduced in Ciona with its transposase enzymes, the transposon is excised from DNA and transposed in Ciona genome.As much as 37% of Minos-injected C. intestinalis transmitted transposon insertions to the subsequent generation.Minos can also be applicable to enhancer trappings.By these techniques, many useful transgenic lines which show tissue-specific reporter gene expression have been generated.These marker lines provide useful resource for future studies of gene expression and functions. Insertional mutagenesis revealed the function of ascidian celluloseCellulose biosynthesis is a major characteristic of tunicates.The genome project of Ciona intestinalis revealed that Ciona has a gene encoding cellulose synthase Ci-CesA.Further study has suggested that Ci-CesA was acquired in ascidians by lateral gene transfer from bacteria.