ASSESSMENT OF PROMOTER TRAP AS A TOOL TO STUDY ZYGOTIC EMBRYOGENESIS IN ARABIDOPSIS-THALIANA

The we of promoter trapping for the study of zygotic embryogenesis was assessed in Arabidopsis thaliana. Plants were transformed with a T-DN A construction containing the uidA reporter gene lacking a promoter Th e object of this study was to look for active transcriptional fusions between plant promoters and the reporter gene. Hundred transformed Ara bidopsis were tested for GUS expression in various organs by fluoromet ry. Sixty-two percent of the transgenic plants expressed GUS in at lea st one organ. Twenty-six percent of the plants expressed GUS in young siliques as well as in other organs and 2% of them showed expression i n young siliques only. The pattern of GUS expression in these 26 lines was visualised by histochemistry. Six showed expression in the embryo : 3 were constitutive 1 had a preferential expression in mature seed, I had a specific expression in the seed tissues and the embryo and in 1 plant, expression was restricted to the embryo. However, none of the m exhibited an expression specific to one stage of embryo development. Within a second set of 186 transformants, a plant showed a specific G US expression in the root tip from the heart stage embryo to the matur e plant and another a specific GUS expression in the suspensor cells. The value of promoter trapping to characterise cell- and tissue-specif ic genes in plants embryos is discussed in relation to similar strateg ies in Drosophila.