title: GIANT EMBRYO encodes CYP78A13, required for proper size balance between embryo and endosperm in rice.
abstract: Among angiosperms there is a high degree of variation in embryo/endosperm size in mature seeds. However, little is known about the molecular mechanism underlying size control between these neighboring tissues. Here we report the rice GIANT EMBRYO (GE) gene that is essential for controlling the size balance. The function of GE in each tissue is distinct, controlling cell size in the embryo and cell death in the endosperm. GE, which encodes CYP78A13, is predominantly expressed in the interfacing tissues of the both embryo and endosperm. GE expression is under negative feedback regulation; endogenous GE expression is upregulated in ge mutants. In contrast to the loss-of-function mutant with large embryo and small endosperm, GE overexpression causes a small embryo and enlarged endosperm. A complementation analysis coupled with heterofertilization showed that complementation of ge mutation in either embryo or endosperm failed to restore the wild-type embryo/endosperm ratio. Thus, embryo and endosperm interact in determining embryo/endosperm size balance. Among genes associated with embryo/endosperm size, REDUCED EMBRYO genes, whose loss-of-function causes a phenotype opposite to ge, are revealed to regulate endosperm size upstream of GE. To fully understand the embryo-endosperm size control, the genetic network of the related genes should be elucidated.
authors.affiliation: DuPont Agricultural Biotechnology, Experimental Station E353, PO Box 80353, Wilmington, DE 19880, USA.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nagasawa
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Hibara
authors.forename: Elmer P
authors.initials: EP
authors.lastname: Heppard
authors.forename: Kent A
authors.initials: KA
authors.lastname: Vander Velden
authors.forename: Stanley
authors.initials: S
authors.lastname: Luck
authors.forename: Mary
authors.initials: M
authors.lastname: Beatty
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nagato
authors.forename: Hajime
authors.initials: H
authors.lastname: Sakai
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D002874:Chromosome Mapping; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D056625:Endosperm / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005838:Genotype; D008969:Molecular Sequence Data; D009154:Mutation; D009928:Organ Specificity; D012275:Oryza / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D012639:Seeds / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D015854:Up-Regulation
chemical_list: D010940:Plant Proteins; D003577:Cytochrome P-450 Enzyme System
keywords: GIANT EMBRYO; cell death; cell size; cytochrome P450; embryo/endosperm size; rice