Plant Molecular Biology 37: 897–910, 1998.
© 1998 Kluwer Academic Publishers. Printed in Belgium.
Eucalyptus has a functional equivalent of the Arabidopsis ﬂoral meristem
identity gene LEAFY
Simon G. Southerton
,Mark R. Olive, Rebecca L. Harcourt
, Xiaomei Zhu, Danny J. Llewellyn, W. James Peacock and Elizabeth S. Dennis
CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia (
author for correspondence; E-mail:
E.Dennis@pi.csiro.au); Present addresses:
Department of Biochemistry, University of Queensland, St. Lucia
Department of Forest Science, Oregon State University, Corvallis, OR 97331-7501, USA;
CSIRO Entomology, P.O. Box 1700 Canberra City, ACT 2601, Australia;
INRA Centre de Bordeaux, UREFV, BP
81, 33883 Villenave d’Ornon, France
Received 28 November 1997; accepted in revised form 11 February 1998
Key words: Eucalyptus globulus, ﬂoral meristem identity gene, ﬂower development, in situ hybridization, LEAFY
Two genes cloned from Eucalyptus globulus, Eucalyptus LeaFy (ELF1 and ELF2), have sequence homology to the
ﬂoral meristem identity genes LEAFY from Arabidopsis and FLORICAULA from Antirrhinum. ELF1 is expressed
in the developing eucalypt ﬂoral organs in a pattern similar to LEAFY while ELF2 appears to be a pseudo gene.
ELF1 is expressed strongly in the early ﬂoral primordium and then successively in the primordia of sepals, petals,
stamens and carpels. It is also expressed in the leaf primordia and young leaves and adult and juvenile trees.
The ELF1 promoter coupled to a GUS reporter gene directs expression in transgenic Arabidopsis in a temporal
and tissue-speciﬁc pattern similar to an equivalent Arabidopsis LEAFY promoter construct. Strong expression is
seen in young ﬂower buds and then later in sepals and petals. No expression was seen in rosette leaves or roots
of ﬂowering plants or in any non-ﬂowering plants grown under long days. Furthermore, ectopic expression of the
ELF1 gene in transgenic Arabidopsis causes the premature conversion of shoots into ﬂowers, as does an equivalent
35S-LFY construct. These data suggest that ELF1 plays a similar role to LFY in ﬂower development and that the
basic mechanisms involved in ﬂower initiation and development in Eucalyptus are similar to those in Arabidopsis.
In the plant species Antirrhinum and Arabidopsis,the
apical shoot meristem initiates lateral primordia that
develop into either shoots or ﬂowers. The develop-
ment of ﬂowers instead of shoots is mediated by the
action of ﬂoral meristem identity genes which include
LEAFY (LFY)inArabidopsis  and its homologue
FLORICAULA (FLO)inAntirrhinum . Inactivation
of the FLO gene in Antirrhinum causes formation of
indeterminate shoots in place of ﬂowers and in Ara-
The nucleotide sequence data reported will appear in the
EMBL, GenBank and DDBJ Nucleotide Sequence Databases under
the accession number AF034806.
bidopsis lfy mutants the structuresthat would normally
develop into ﬂowers develop into structures intermedi-
ate between shoots and ﬂowers. APETALA1 (AP1)is
asecond ﬂoral meristem identity gene in Arabidopsis
that acts together with LFY to determine meristem fate
. When the LFY and AP1 genes are both disrupted
 there is a complete lack of ﬂower development,
and only inﬂorescence shoots are found.
FLO and LFY share 70% amino acid identity and
each has a proline rich region and an acidic domain
which indicates they may have a role as transcriptional
activators . In Arabidopsis, LFY has been found to
activate homeotic genes which regulate ﬂoral organo-
genesis . Both LFY and FLO are expressed in