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发表于 2011-10-11 08:27 |只看该作者 |倒序浏览 |打印

本帖最后由细胞海洋于 2011-10-11 09:11 编辑 + O. A6 C3 d! O$ i" Q

The discovery of DNA as the genetic material brought great hope to scientists all over the4 p8 B0 S9 |& k1 n
world. It was believed that many of the lingering questions in genetics and the mechanisms* _, [1 f2 p# v7 S
of heredity would finally be answered. However, as often is the case in science, more questions
arose out of this discovery. What defines a gene? What are the mechanisms of gene
regulation? Further discovery and technological innovations brought about sequencing
techniques that allowed the study of complete genomes from many organisms, including
Arabidopsis and humans. Despite all the excitement surrounding these technologies, many
features of the genome remained unclear. Peculiar characteristics in genome composition4 G) o3 f9 X3 y6 Z* I8 k  s
such as significant redundancy consisting of many repetitive elements and noncoding& [/ w4 R' L" c2 u/ ]5 V' M
sequences, active transcriptional units with no protein product, and unusual sequences in
promoter regions added to the mysteries of genetic make-up and gene regulation. Indeed,$ n6 J7 h- M- G4 [4 [' O% E
the more we discovered about the genome, the more difficult it became to understand the
complexity of cellular function and regulation.+ n' f4 L" N% m" G7 }* Q) N
Out of the study of the intricacies of the genome and gene regulation, arose a new
science that was independent of actual DNA changes, but critical in maintaining gene
regulation and genetic stability. Epigenetics, literally translated as “above genetics,” is the
science that describes the mechanisms of heritable changes in gene regulation that does  \) A* D8 R2 Q1 q2 _/ E3 m
not involve modifications of DNA sequence. These changes may last through somatic cell% A9 K5 m' |: l; V. J; E
division and, in some cases, throughout multiple generations.2 o- y( b- t% N: f
Epigenetics is perhaps one of the most popular and quickly evolving fields of modern
science. Despite the fact that the ideas behind epigenetics had already been developing in) e( m6 z8 O" |9 _5 c6 [. g% B' a7 x5 s
the late nineteenth and early twentieth centuries, major advances have only occurred6 \) |6 F  ~2 l) a8 Z3 o
within the last 10–15 years as the mechanisms surrounding epigenetic regulation began to+ \1 c! n, P, a( q0 t3 |
be uncovered. It was hoped by many that the mysteries of gene regulation and inheritance
that remained unanswered would finally be elucidated with the help of this new science.
Since, the understanding of the contribution of epigenetic regulation to cell function has
helped scientists from many distinct fields of research such as molecular biology, population
genetics, microbiology, ecology, developmental biology, and evolution.. Z' Z0 z, _8 Z: ^$ u
Gene silencing as an epigenetic mechanism to control gene expression was first
described in plants. This occurred with the beginning of the era of plant transgenesis, and1 K+ d* I9 j, w
almost undermined the new paradigm of improvement of plant performance via transgenic1 h: P1 A9 Z- ~
techniques. Silencing was a serendipitous discovery, as this finding revitalized the/ g4 G$ J5 t& X
field of epigenetics. Phenomena such as plant acclimation and adaptation to stress, hybrid: l2 i8 B  K) C9 _1 ?. A' s- m" }% @5 Y
and heterozygote vigor (heterosis), plant tolerance to viral infection, transgenerational
changes in genome stability, paramutations, among others, are now considered excellent
candidates for regulation via epigenetic mechanisms. Future studies involving various protocols
for the analysis of methylation patterns, histone modifications, chromatin structure,  W! l4 ]9 p1 G0 t  f( S* v5 N) v
and small RNA expression, the hallmarks of epigenetic regulation, will undoubtedly help5 R2 A7 }$ N4 b% K
to explain these phenomena. It will be exciting to discover how plants utilize these mechanisms
to adapt to stress, and how we can manipulate these characters for the generation of
better and hardier crops.
vi Preface) m1 b/ r7 g* g9 Y
In this book we have collected a variety of protocols for the study of the function of
small noncoding RNAs, DNA methylation, and histone modifications in plants. Where possible' k; B3 D+ J  X7 b, R4 Q
and appropriate, we presented several protocols with different degrees of complexity.
We also include protocols for plant transgenesis and the analysis of genome stability, with a
discussion for their applications to epigenetic studies. It was our aim to put together a single
manual that researchers in the field of plant epigenetics can turn to in hopes to answer the
many yet undiscovered and unexplained phenomena in plant biology.
Lethbridge, AB, Canada Igor Kovalchuk
Franz J. Zemp

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