The major outer membrane protein (MOMP) of Chlamydia trachomatis is a highly antigenic and hydrophobic transmembrane protein. Our attempts to express the full-length protein in a soluble form in Escherichia coli and in transgenic plants failed. A chimeric gene construct of C trachomatis serovar E MOMP was designed in order to increase solubility of the MOMP protein but with retained antigenicity. The designed construct was successfully expressed in E. coil, in Arabidopsis thaliana, and in Daucus carota. The chimeric MOMP expressed in and purified from E. coil was used as antigen for production of antibodies in rabbits. The anti-chimeric MOMP antibodies recognized the corresponding protein in both E. coli and in transgenic plants, as well as in inactivated C. trachomatis elementary bodies. Transgenic Arabidopsis and carrots were characterized for the number of MOMP chimeric genetic inserts and for protein expression. Stable integration of the transgene and the corresponding protein expression were demonstrated in Arabidopsis plants over at least six generations. Transgenic carrots showed a high level of expression of the chimeric MOMP - up to 3% of TSP. (C) 2011 Elsevier Inc. All rights reserved.