Biology Reference
In-Depth Information
expression of a large number of genes during development. Whereas some
pathways are based on seemingly conserved mechanisms, others rely on
more divergent regulators that might have evolved to accompany distinct
interpretations of multicellularity. Significant advances in our understand-
ing of epigenome organization and chromatin-associated pathways indi-
cate that divergent innovations might be exacerbated in plants, perhaps
due to their extensive developmental plasticity and the necessity to adjust
to environmental changes. Although some principles are beginning to
emerge, thanks in part to large-scale epigenomic mapping and also to
the extensive analysis of isolated loci, such as
FLC
, several key questions
remain. At the molecular level, the mechanisms underlying the recruit-
ment or targeting of most chromatin modifiers are largely unknown.
Understanding these mechanisms and the activities responsible for remov-
ing chromatin marks or erasing chromatin states will be pivotal in order to
interpret the dynamics of epigenomes during developmental stages. Deter-
mining the extent of this dynamics requires substantial improvement of the
temporal and spatial resolution of epigenomic data, which can be achieved
by using cell type-specific methodologies and by developing refined model
systems. In addition, the interplay between epigenome dynamics and
upstream signal transduction pathways as well as parallel gene regulatory
networks is poorly understood. Finally, analyzing the epigenomes of
Arabidopsis
relatives and more distant species is necessary in order to
reveal conservation or diversity in the relationship between genotype,
epigenotype and phenotype.
Recent efforts in
Arabidopsis
have suggested that epigenetic variation on
its own can be a substantial source of heritable phenotypic variation (
Becker
et al., 2011; Johannes et al., 2009; Richards, 2006, 2011; Schmitz et al.,
2011; Weigel &Colot, 2012
). The ability of the plant epigenome to respond
to the environment and the fact that plants do not segregate their germline
early in development open up the exciting possibility that epigenetic vari-
ation provides a flexible means of contributing significantly to plant adapta-
tion and evolution.
ACKNOWLEDGMENTS
We apologize to those researchers whose work could not be covered due to space limitations.
We thank V. Colot and M. Mirouze for critical reading of this chapter. Work in the D.G. lab
is supported by ANR (Agence Nationale de la Recherche) and the Institut de Recherche
pour le D
´
veloppement (IRD). Work in the F.R. lab is supported by ANR, the Centre
National de la Recherche Scientifique (CNRS) and the European Union Network of
Excellence “EpigeneSys”.
