CHARACTERIZATION OF REM GENES INVOLVED IN THE REPRODUCTIVE DEVELOPMENT OF ARABIDOPSIS THALIANA

Role of REM34, REM35 and REM36 in gametophytes development. The REproductive Meristem (REM) gene family encodes for transcription factors belonging to the B3 DNA binding domain superfamily. In Arabidopsis thaliana, this family is composed of 45 members, preferentially expressed during flower, ovule, and seed developments. Only a few members of this family have been functionally characterized: VERNALIZATION1 (VRN1) and, most recently, TARGET OF FLC AND SVP1 (TFS1), which are involved in the regulation of flowering time and VERDANDI (VDD) which, together with VALKYRIE (VAL) controls the death of the synergid cell in the female gametophyte. We investigated the role of REM34, REM35, and REM36, three closely related and linked on chromosome 4 genes with similar expression profiles during the reproductive development of Arabidopsis. The functional characterization of REM34, REM35 and REM36 presented several challenges, as these genes are in linkage in the genome and redundant. We thus developed two different approaches, the first based on a multiplexed RNA interference (RNAi) technology and the second on the fusion of REM34 with the EAR repressive domain, to modify their expression and identifying their role during inflorescence development. Plants generated with both methods were characterized by a partial sterility. An in situ hybridization analysis showed that REM34, REM35 and REM36 share the same expression pattern throughout reproductive organs development. As these genes were found to be expressed both in female and male reproductive tissues, the developmental steps of both gametes were followed in both the REM_RNAi and 35S:REM34-EAR lines; these analyses clearly showed that the partial sterility of these lines is caused by a postmeiotic block in both female and male gametophytes. Furthermore, protein interaction assays revealed that REM34 and REM35 interact, which suggests that they work together during the first stages of gametogenesis.