Reference "How is embryo size genetically regulated in rice?"

Reference ID

1478

Title

How is embryo size genetically regulated in rice?

Source

Development (Cambridge, England), 1996, vol. 122, pp. 2051-2058

Authors (4)

Hong-S-K	Kitano-H
Satoh-H	Nagato-Y

Abstract

It is unclear how embryo size is genetically regulated in plants. Since cereals
have a large persisting endosperm, it is expected that embryo size is affected
by endosperm development. Nine single recessive mutations, four reduced embryo
mutations representing three loci, REDUCED EMBRYO1, REDUCED EMBRYO2 and REDUCED
EMBRYO3, four giant embryo mutations derived from a single locus GIANT EMBRYO,
and one endospermless mutation endospermless1-2 were analyzed. Every reduced
embryo mutation caused reduction of all the embryonic organs including apical
meristems and the enlargement of the endosperm. The giant embryo mutants have a
reduced endosperm and an enlarged scutellum. However, shoot and radicle sizes
were not affected. All the reduced embryo and giant embryo mutations did not
largely affect postembryonic development. Accordingly, the expression of genes
analyzed are seed- specific. In reduced embryo and giant embryo mutations,
abnormalities were detected in both embryo and endosperm as early as 2 days
after pollination. endospermless1-1 resulted in an early loss of endosperm,
yielding a giant embryo, suggesting that embryo growth was physically limited by
the endosperm. A double mutant between giant embryo-2 and club-shaped embryo1-1,
which has a normal endosperm and a minute undifferentiated embryo, resulted in a
club-shaped embryo1-1 embryo and a reduced endosperm of giant embryo-2,
indicating that GIANT EMBRYO regulates the endosperm development. Double mutants
between giant embryo-2 and three reduced embryo mutants exhibited the reduced
embryo phenotype in both embryo and endosperm, suggesting that reduced embryo
mutations cause the enlarged endosperm. Further, a double mutant of reduced
embryo3 and endospermless1-1 showed the enlarged embryo in endospermless seed.
This confirms that reduced embryo3 does not regulate embryo size but enlarges
endosperm size. Together with the results of the other double mutant analysis,
REDUCED EMBRYO1, REDUCED EMBRYO2, REDUCED EMBRYO3 and GIANT EMBRYO are concluded
to regulate endosperm development.