PDF电子书：Plant Epigenetics

lvlinqishi2011

) J; J1 Q1 G  B* W0 _! `+ R) G3 Q- I; j& N& g6 o" i
The discovery of DNA as the genetic material brought great hope to scientists all over the# ~5 ?7 g: L1 u4 k6 {
world. It was believed that many of the lingering questions in genetics and the mechanisms) c8 Y. e! F' |1 {
of heredity would finally be answered. However, as often is the case in science, more questions) h( t# o7 Z. |) E4 B1 x  @9 l% ?
arose out of this discovery. What defines a gene? What are the mechanisms of gene
2 U2 \/ C# W  c1 F, [2 {( v. d$ Yregulation? Further discovery and technological innovations brought about sequencing
! n0 P; p! Z+ @- gtechniques that allowed the study of complete genomes from many organisms, including
2 b4 |9 Q' i+ g7 T# h, O* {Arabidopsis and humans. Despite all the excitement surrounding these technologies, many
  D3 D4 W/ S/ e. O7 |& ofeatures of the genome remained unclear. Peculiar characteristics in genome composition
4 u$ \" Q, h  ^. ?. A  ?such as significant redundancy consisting of many repetitive elements and noncoding+ L) K) V  x) i4 ?1 \
sequences, active transcriptional units with no protein product, and unusual sequences in
: b1 M$ a4 B; u1 K) W8 ypromoter regions added to the mysteries of genetic make-up and gene regulation. Indeed,. T  V# p- |3 Z1 n6 a; ^
the more we discovered about the genome, the more difficult it became to understand the( C7 r2 w/ ~$ n) p0 w
complexity of cellular function and regulation.
( Y" l6 y- z: L: O1 Y7 rOut of the study of the intricacies of the genome and gene regulation, arose a new
* v1 a4 E2 @1 D6 _" w  p* }3 vscience that was independent of actual DNA changes, but critical in maintaining gene0 G# [6 P/ u8 s
regulation and genetic stability. Epigenetics, literally translated as “above genetics,” is the* J8 H. c1 C) b# V* k7 m) W
science that describes the mechanisms of heritable changes in gene regulation that does# V: ^: N- }6 {6 z% y0 ^
not involve modifications of DNA sequence. These changes may last through somatic cell
( _# m2 g; ~7 T7 O/ u5 K" M, odivision and, in some cases, throughout multiple generations.* i' Q1 ]1 z! I2 p
Epigenetics is perhaps one of the most popular and quickly evolving fields of modern- P5 a( r- G6 w% v8 _
science. Despite the fact that the ideas behind epigenetics had already been developing in
6 S( `7 |! y/ G# E, _% Y; `$ Pthe late nineteenth and early twentieth centuries, major advances have only occurred
# W$ `9 u6 {: ?7 R% s9 rwithin the last 10–15 years as the mechanisms surrounding epigenetic regulation began to4 \) q  `7 q" A6 Q
be uncovered. It was hoped by many that the mysteries of gene regulation and inheritance) N, R! q, O& s% _$ _: T& N% u
that remained unanswered would finally be elucidated with the help of this new science.5 ~7 g% Q+ X0 u: d
Since, the understanding of the contribution of epigenetic regulation to cell function has0 n$ {% ?0 }" U; q3 W3 D  s% l
helped scientists from many distinct fields of research such as molecular biology, population4 v1 r" W, F8 S" @2 L' }
genetics, microbiology, ecology, developmental biology, and evolution.$ k, E3 `/ N+ [" m8 ?% G/ _4 R
Gene silencing as an epigenetic mechanism to control gene expression was first
+ U/ Z: c& X1 y: n0 F# ddescribed in plants. This occurred with the beginning of the era of plant transgenesis, and
3 B, l4 \$ k# }+ _  W1 _% Q7 ]- Zalmost undermined the new paradigm of improvement of plant performance via transgenic$ H' Q8 n6 T) e$ {: t9 T
techniques. Silencing was a serendipitous discovery, as this finding revitalized the
$ w$ o4 A# i: g! rfield of epigenetics. Phenomena such as plant acclimation and adaptation to stress, hybrid4 E+ w  |9 W1 T' _+ n
and heterozygote vigor (heterosis), plant tolerance to viral infection, transgenerational
* o* D4 j& R- Pchanges in genome stability, paramutations, among others, are now considered excellent4 t$ B. u% q- ^: |$ I4 p
candidates for regulation via epigenetic mechanisms. Future studies involving various protocols+ a, [! n1 _/ J  g
for the analysis of methylation patterns, histone modifications, chromatin structure,% V/ X' a* p* I. o8 I
and small RNA expression, the hallmarks of epigenetic regulation, will undoubtedly help
* a! R0 U8 |9 O* L, nto explain these phenomena. It will be exciting to discover how plants utilize these mechanisms
) s) P& n' F" S, @to adapt to stress, and how we can manipulate these characters for the generation of
. m1 c5 g0 R1 V* R5 z; ebetter and hardier crops.
/ M5 V  b& K+ u" }6 C7 Evi Preface
% X3 p/ L- R' u, a4 }In this book we have collected a variety of protocols for the study of the function of4 I' {* T0 a6 ^3 a6 u: L3 }% ^
small noncoding RNAs, DNA methylation, and histone modifications in plants. Where possible, U0 q) E& e  f8 }1 M: X
and appropriate, we presented several protocols with different degrees of complexity.9 W4 l- k9 G+ r/ f9 q& N
We also include protocols for plant transgenesis and the analysis of genome stability, with a! W8 m2 O2 D6 A+ y4 G. a7 K9 L5 ]
discussion for their applications to epigenetic studies. It was our aim to put together a single, x$ H5 r7 l8 k. X0 M. p# z5 R: h3 M* W
manual that researchers in the field of plant epigenetics can turn to in hopes to answer the; A# r: o1 U3 u$ a6 L0 ?
many yet undiscovered and unexplained phenomena in plant biology.
9 Y1 t: [8 c& X  p/ Q# r7 ILethbridge, AB, Canada Igor Kovalchuk3 ^) N) |) Q; w- k' }% u
Franz J. Zemp
* C( I' x4 O/ Y
9 `$ B7 K! T. x9 `5 ]* P  {+ U' q[hide][/hide]