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Maize Genomics and Genetics 2012, Vol.3, No.3, 13
-
21
ISSN 1925-1971 http://mgg.sophiapublisher.com
13
Research Report Open Access
Genetic Imprinting in Maize
Bhavani P.
1
, Harinikumar K.M.
1
, Shashidhar H.E.
1
, Sajad Majeed Zargar
2
1 Department of Biotechnology, University of Agricultural Sciences, GKVK, Bangalore, Karnataka-560065, India
2 School of Biotechnology, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha, Jammu, J&K-180009, India
Corresponding author email: deerabagowda@gmail.com;
Authors
Maize Genomics and Genetics, 2012, Vol.3, No.3 doi: 10.5376/mgg.2012.03.0003
Received: 01 Aug., 2011
Accepted: 07 Aug., 2011
Published: 13 Aug., 2012
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Bhavani et al., 2012, Genetic Imprinting in Maize, Maize Genomics and Genetics, Vol.3, No.3, 13-21 (doi: 10.5376/mgg.2012.03.0003)
Abstract
Genetic imprinting is the epigenetic phenomenon observed in flowering plants including maize in which,
an allele shows differential expression depending on the parent it is inherited. Imprinted genes are modified during
gametogenesis so that only paternal or maternal allele is expressed after fertilization. This review focuses on the
major processes involved in the regulation of imprinting like DNA methylation, covalent modifications of
histones and chromatin remodeling citing examples of maize. This review also summarizes theimprinted genes
that have been reported in maize including
Fie1
,
Fie2
,
Peg1
,
Nrp1
,
Mez1
,
Meg1
,
Mee1
,
VIP5
and
Yuc8
.
Keywords
Maize; Genetic imprinting; Epigenetics; Histone methylation
Background
Transfer of acquired characters of an individual within
the lifetime without the change in DNA sequence is
termed as “epigenetics” unlike Mendelian genetics,
which describes the inheritance of genes that encode
specific traits (Ho and Burggren, 2010). Though, the
“theory of acquired inheritance” was given by
Lamarck way back in 1809 and endorsed by Lysenko
(Lysenko, 1948). The concept did not gain much
needed attention due to the more convincing evidence
obtained by the experiments of Mendel and predece-
ssors (detailed in Weldon, 1902). But inheritances
of certain traits like veliger development in snail
(Freeman and Lundelins, 1982), epigenetic abberrations
and spermatogenesis (Singh et al., 2011), impact of
exposure of parents to environmental stress on
development of resistance to the environment stress in
the progeny (Agrawal et al., 1999) has opened up a
new dimension of this, much ignored theory of
science. The term “epigenetics” was first coined by
Waddington (Waddington, 1942), which literally means
“above stress”. Waddington defined epigenetics as
“environment-gene interactions that induce develop-
mental phenotype”. But the recent and the most
widely accepted definition is „„an epigenetic trait is a
stably heritable phenotype resulting from changes
in a chromosome without alterations in the DNA
sequence” (Singh et al., 2011). The modifications that
add this extra piece of information without changing
the DNA sequences are DNA methylation, histone
modifications and chromatin remodeling proteins.
Therefore, the genome is the sum total of the infor-
mation encoded by the nucleotide sequences while the
epigenome is the amassed effect of these DNA and
histone modifications on gene expression without
affecting the base sequence. Thus, imprinted expression
states are under epigenetic control (Springer and
Gutierrez-Marcos, 2009). These states can have
shortterm and long-term effects and could be trans-
generational (Anway et al., 2005).
In plants, the evidences of genetic imprinting have
been observed in triploid endosperm and not in
vegetative tissues (Gehring et al., 2004; Gehring et al.,
2009; Huh et al., 2008; Jullien and Berger, 2009;
Springer and Gutierrez-Marcos, 2009). Since the
active and silenced state of gene is present in the same
nucleus, there is the possibility of existence of distinct
mechanisms to maintain the epigenetic state between
the parental alleles. Maize (
Zea mays
L.) provides an
excellent model to study the role of epigenetic