Objective:
To reduce potentially negative effects of transgene insertion and genomic presence.

Approach:
We will investigate the use of novel unidirectional recombinases Bxb1, CinH, ParA and phiC31 to implement a Recombinase-Mediated Cassette Exchange (RMCE) technique for precise integration with simultaneous marker removal. 1) To generate transgenic founder citrus Carrizo citrange lines containing the RMCE genetic platform for precise targeting. 2) To demonstrate proof of concept that the dual unidirectional RMCE is functional in Carrizo citrange. Single copy transgenic Carrizo citrange founder lines will be generated containing the selection gene cassette flanked by fused recognition sites. An exchange venctor will be biolistcally transformed into the various Carrizo citrange founder lines. RMCE will be examined by negative slection and used to score the most effective pairs. The most effective Carrizo citrange founder lines and recombinase pairs will be published and made publicly available.