The Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR KINASE 1 gene is expressed in developing ovules and embryos and enhances embryogenic competence in culture

We report here the isolation of the Arabidopsis SOMATIC EMBRYOGENESIS RECEP TOR-LIKE KINASE 1 (AtSERK1) gene and we demonstrate its role during establi shment of somatic embryogenesis in culture. The AtSERK1 gene is highly expr essed during embryogenic cell formation in culture and during early embryog enesis. The AtSERK1 gene is first expressed in planta during megasporogenes is in the nucleus of developing ovules, in the functional megaspore, and in all cells of the embryo sac up to fertilization. After fertilization, AtSE RK1 expression is seen in all cells of the developing embryo until the hear t stage. After this stage, AtSERK1 expression is no longer detectable in th e embryo or in any part of the developing seed. Low expression is detected in adult vascular tissue. Ectopic expression of the full-length AtSERK1 cDN A under the control of the cauliflower mosaic virus 35S promoter did not re sult in any altered plant phenotype. However, seedlings that overexpressed the AtSERK1 mRNA exhibited a 3- to 4-fold increase in efficiency for initia tion of somatic embryogenesis. Thus, an increased AtSERK1 level is sufficie nt to confer embryogenic competence in culture.