Аннотация:Summary Fusion of the egg and the sperm cells in plants produces a zygote that develops into an embryo. Screening of ethyl methanesulfonate‐mutagenized populations of Arabidopsis led to the identification of EMBRYONIC FACTOR 1 ( FAC1 ), a locus that gives a zygote‐lethal phenotype when mutated. The FAC1 gene was identified by positional cloning and confirmed by a genetic complementation test against a T‐DNA insertion allele. It encodes an AMP deaminase (AMPD) that is known in human and yeast to convert AMP to IMP to maintain the energy potential. Expression of FAC1 in a yeast AMPD mutant after removal of its N‐terminal putative transmembrane domain complemented the mutant phenotype, suggesting a functional conservancy but a structural divergence through evolution. Although a low level of FAC1 expression was observed in all organs tested, using a reporter construct we observed a significantly increased FAC1 expression in the zygote, early embryo and endosperm. Furthermore, during somatic embryogenesis, a high level of FAC1 expression was observed in developing embryos including putative embryogenic cells. FAC1 , therefore, represents one of the earliest expressed genes known in plants. It may act through AMP depletion to provide sufficient energy for the zygote to proceed through development.
