9
Stranger than Fiction: Loss
of MADS-Box Genes During
Evolutionary Miniaturization
of the Duckweed Body Plan
Loss of MADS-Box Genes in Duckweeds
Lydia Gramzow and Günter Theißen
Abstract
Duckweeds (Lemnoideae or Lemnaceae) are
unusual flowering plants. They all lack a stem,
many species even do not have roots, and
most of them flower only rarely, if at all.
Evolution of duckweeds obviously involved
extreme miniaturization and simplification of
their structure and life cycle. This raises the
question as to whether the evolutionary
changes of the duckweed body plan were
accompanied, and thus potentially causally
linked, to a loss of function of genes that
control the development of affected structures.
MADS-box genes are involved in the control
of many developmental processes in flowering
plants, including root, flower, and fruit development. Their phylogeny is quite well known
and reveals a fairly strong correlation between
some gene clades and function. Therefore, we
used the available genome sequences of
several duckweed species to test as to whether
the loss of specific MADS-box genes can be
linked to the reduction of morphological
structures. In all duckweed genomes analysed,
5 of the 17 clades of MIKC
C -group
MADS-box genes that probably existed in
the most recent common ancestor of extant
flowering plants, appear to be absent. Our
analyses thus demonstrate that duckweeds are
the plant taxon with the lowest number of
MIKC-type MADS-box gene clades of all
flowering plants that were investigated so far.
While AGL15-like genes have probably been
lost in the stem group of extant monocots
already, and FLC-like genes have been lost in
the stem group of the order Alismatales (to
which duckweeds belong), AGL9- (SEP3-),
AGL12- and OsMADS32-like genes were lost
very likely in the stem group of extant
duckweeds. The potential functional relevance
of our findings is discussed. For example, the
loss of AGL12-like genes might be linked to
the vestigial or absent root formation in
duckweeds.
9.1 Small Is Beautiful: Evolutionary
Developmental Biology
of the Duckweed Body Plan
Duckweeds are strange plants. People easily
assume that they are algae, ferns or mosses, but
in fact, they are flowering plants (angiosperms),
even though many of them flower only occasionally or never. Actually, duckweeds are the
smallest and morphologically simplest flowering
L. Gramzow Á G. Theißen (&)
Matthias Schleiden Institute - Genetics, Friedrich
Schiller University, Philosophenweg 12, 07743 Jena,
Germany
e-mail: guenter.theissen@uni-jena.de
© Springer Nature Switzerland AG 2020
X. H. Cao et al. (eds.), The Duckweed Genomes, Compendium of Plant Genomes,
https://doi.org/10.1007/978-3-030-11045-1_9
91
Stranger than Fiction: Loss
of MADS-Box Genes During
Evolutionary Miniaturization
of the Duckweed Body Plan
Loss of MADS-Box Genes in Duckweeds
Lydia Gramzow and Günter Theißen
Abstract
Duckweeds (Lemnoideae or Lemnaceae) are
unusual flowering plants. They all lack a stem,
many species even do not have roots, and
most of them flower only rarely, if at all.
Evolution of duckweeds obviously involved
extreme miniaturization and simplification of
their structure and life cycle. This raises the
question as to whether the evolutionary
changes of the duckweed body plan were
accompanied, and thus potentially causally
linked, to a loss of function of genes that
control the development of affected structures.
MADS-box genes are involved in the control
of many developmental processes in flowering
plants, including root, flower, and fruit development. Their phylogeny is quite well known
and reveals a fairly strong correlation between
some gene clades and function. Therefore, we
used the available genome sequences of
several duckweed species to test as to whether
the loss of specific MADS-box genes can be
linked to the reduction of morphological
structures. In all duckweed genomes analysed,
5 of the 17 clades of MIKC
C -group
MADS-box genes that probably existed in
the most recent common ancestor of extant
flowering plants, appear to be absent. Our
analyses thus demonstrate that duckweeds are
the plant taxon with the lowest number of
MIKC-type MADS-box gene clades of all
flowering plants that were investigated so far.
While AGL15-like genes have probably been
lost in the stem group of extant monocots
already, and FLC-like genes have been lost in
the stem group of the order Alismatales (to
which duckweeds belong), AGL9- (SEP3-),
AGL12- and OsMADS32-like genes were lost
very likely in the stem group of extant
duckweeds. The potential functional relevance
of our findings is discussed. For example, the
loss of AGL12-like genes might be linked to
the vestigial or absent root formation in
duckweeds.
9.1 Small Is Beautiful: Evolutionary
Developmental Biology
of the Duckweed Body Plan
Duckweeds are strange plants. People easily
assume that they are algae, ferns or mosses, but
in fact, they are flowering plants (angiosperms),
even though many of them flower only occasionally or never. Actually, duckweeds are the
smallest and morphologically simplest flowering
L. Gramzow Á G. Theißen (&)
Matthias Schleiden Institute - Genetics, Friedrich
Schiller University, Philosophenweg 12, 07743 Jena,
Germany
e-mail: guenter.theissen@uni-jena.de
© Springer Nature Switzerland AG 2020
X. H. Cao et al. (eds.), The Duckweed Genomes, Compendium of Plant Genomes,
https://doi.org/10.1007/978-3-030-11045-1_9
91