Agriculture Reference
In-Depth Information
alackof functionalcompatibilityinhighlydivergentallelicproductsthat
participate in multimeric complexes (Dilkes and Comai 2004).
VI. ADAPTATION IS A FORM OF DEVELOPMENT
A. Environment Adaptation Modi
es Development
by Heterochrony
There are still many unknown details of the role of epigenetics in the
dramatic levels of phenotype change or adaptation that allows survival
in extreme environments (Chinnusamy and Zhu 2009a; Zhang et al.
2013). Epigenetically controlled phenotype diversity, especially in
plants, has important implications for agriculture. The ability of plants
(crops) to survive and perform in extreme environments may largely
depend on epigenetic phenomena, because the epigenetic system has
the major role of mediating how the genome is read in response to
the environment. There has been little serious consideration of how
environmental responses and adaptation, or their relationships to
evolution are important components of ontogeny. Recently the con-
nection between developmental state and environmental adaptation
has received greater attention (Grafi
et al. 2011; Sugimoto et al. 2011).
The ability to adapt to a changing environment may rely on dedif-
ferentiation and/or redifferentiation into an adapted (tolerant) epige-
netic state. Entering the cell cycle to be able to initiate epimark changes
may be an important or even required step in adaptation (Hasegawa
et al. 1986; Miguel and Marum 2011). Establishing a pluripotent status
in response to an extreme environment also appears to allow cells to
readjust developmental programs and enter a new metastable tolerant
phenotypic state (Huh et al. 2002; Feil and Fraga 2012). Heterochronic
adjustment of development may also be an important feature of sub-
cellular adjustment to saline conditions (Yokoi et al. 2002; Geuten
and Coenen 2013).
If the environment is able to canalize (direct) development to a state
that is more suitable for that particular environment, any mutations that
would control epigenetics through canalization and stabilize the new,
more
fit developmental state by genetic assimilation as predicted by
Baldwin, Waddington, Smaulhauser, McClintock, and others, would
have major effects on crop performances in extreme environments. In
consideration of this possibility (Amzallag 2005), it has been argued that
survival and growth in stressful environments has less to do with special
“
stress tolerance
”
genes that produce special biochemistry, metabolism,
