Reference "Characterization of three GLOBOSA-like MADS-box genes from maize: evidence for ancient paralogy in one class of floral homeotic B-function genes of grasses"

Reference ID

7518

Title

Characterization of three GLOBOSA-like MADS-box genes from maize: evidence for ancient paralogy in one class of floral homeotic B-function genes of grasses

Source

Gene, 2001, vol. 262, pp. 1-13

Authors (6)

Munster-T	Wingen-L-U
Faigl-W	Werth-S
Saedler-H	Theissen-G

Abstract

Floral homeotic B-function genes are involved in specifying the identity of
petals and stamens during flower development in higher eudicotyledonous plants.
Monocotyledonous plants belonging to the grass family (Poaceae) have very
similar B-function genes, except that these genes specify lodicules rather than
petals. All B-function genes known so far are members of the MADS-box gene
family encoding transcription factors. In some eudicot model systems such as
Arabidopsis and Antirrhinum, the B-function is provided by heterodimeric protein
complexes encoded by one DEF- and one GLO-like gene. In several different
lineages of flowering plant species, however, more than one DEF- or GLO-like
gene is found. A known example is the monocot model system rice, which contains
two GLO-like genes, termed OSMADS2 and OSMADS4. Duplications of floral homeotic
genes may have played a critical role in the diversification of floral homeotic
functions and thus the evolution of flowers. In order to date the gene
duplication event that gave rise to these two genes, we cloned cDNAs of three
different GLO-like genes from maize, a distant relative of rice within the
Poaceae family. Phylogeny reconstructions and chromosomal mapping indicate that
one of these genes, named ZMM16, is orthologous to OSMADS2, and that the other
two, ZMM18 and ZMM29, are probably orthologous to OSMADS4. The gene duplication
which gave rise to OSMADS2- and OSMADS4-like genes occurred probably after the
split of the lineages that resulted in extant Liliaceae and Poaceae, but before
the separation of the lineages that gave rise to extant maize and rice about 50
MYA. Northern and in situ hybridization studies demonstrated that the maize
genes are expressed in lodicules, stamens and carpels throughout spikelet
development in male and female inflorescences. The GLO-like genes from rice have
very similar patterns of mRNA accumulation. In addition, ZMM16 shows also weak
expression in vegetative organs. Conservation of the expression in lodicules and
stamens is in perfect agreement with a floral homeotic B-function of the GLO-
like genes in grasses. The conserved expression in carpels is discussed.
Moreover, circumstantial evidence for a functional diversification of GLO-like
genes in grasses is provided.