EMBRYONIC FACTOR 1 encodes an AMP deaminase and is essential for the zygote to embryo transition in Arabidopsis.
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.
Xu
Jun
J
Cluster of Plant Developmental Systems, Plant Research International, PO Box 16, 6700 AA Wageningen, The Netherlands.
Zhang
Hai-Ying
HY
Xie
Cong-Hua
CH
Xue
Hong-Wei
HW
Dijkhuis
Paul
P
Liu
Chun-Ming
CM
D000659:AMP Deaminase / Q000235:genetics* / Q000502:physiology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D015394:Molecular Structure; D009154:Mutation; D010641:Phenotype; D012639:Seeds / Q000201:enzymology / Q000254:growth & development* / Q000648:ultrastructure; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D000659:AMP Deaminase; C503078:FAC1 protein, Arabidopsis