Agriculture Reference
In-Depth Information
Robertsons Mutator in controlling
flower development in plants (Liu
et al. 2004; Tsaftaris et al. 2008; Lisch 2013). Also, several examples of
environment-induced retrotransposons and associated epigenetic
changes in the genome have been reported (Mhiri et al. 1997; Grand-
bastien 1998; Takeda et al. 1999). Many of the second-site gene suppres-
sors of PEVwere revealed to be part of the epigenetic machinery. Some of
these including ENHANCER of ZESTE ([E (Z)] and TRITHORAX have
been shown to be connected to TE insertion events (Jones and Gelbart
1993; Tschiersch et al. 1994). Telomere position effect on loci is also
associated with TE insertions (Cryderman et al. 1999; Ko
er et al. 2012).
Sequence repeat-induced changes in chromatin and subsequent marker
gene expression also has been observed in plants to be controlled by
genes containing a SET domain, distinctive of the related to suppressor
variegations, su (var) genes in animals (Baumbusch et al. 2001; Kuhl-
mann and Mette 2012; Yun et al. 2012). Genes involved in animal
fertility (Kuramochi-Miyagawa et al. 2004) also have transcripts with
retrotransposons embedded, such as intercisternal A Particle (IAP), and
Long Interdispersed Nucleotide Element (Line 1).
Many important features of adaptation to the environment also have
been connected to DNA duplications as evidenced by widely variant
ploidy levels within species (Stebbins 1971; Hilu 1993; Masterson 1994;
Gaut 2001; Chen 2007). In fact, ploidy changes are considered to be a
major contribution to adaptation (Arnold 2004; Mable 2013) and speci-
ation, as Ohno originally predicted in his topic (Ohno 1970). Sexual
reproduction and the dsRNA silencing systems each may therefore be
closely connected to environmental cues (Olmedo-Mon
l et al. 2010),
both likely originating as defenses against invasive DNA, and thus both
becoming strategic responses to a changing environment and allowing
new niches to be occupied. This would place the extant gene silencing
pathways in the most highly evolved and preeminent position to not
only control development but also to control environmental responses
and adaptation through a nucleotide pairing system that uses the gene
silencing pathways to convey information to guide the somatic devel-
opment program. It appears that the double strand helix structure of
DNA not only is essential to provide the elegant mechanism of DNA
replication and transcription/translation but also is a fundamental basis
for controlling speci
city of DNA reading.
C. Sex and Genome Invasion
Once considerable allelic diversity accumulates in the haploid/diploid
system,
the opportunity arises for allele-speci
c expression and
