Current Trends in the Embryology of Angiosperms

534 Pages·2001·44.41 MB·English

by  Darlene Southworth

Current Trends in the Embryology of Angiosperms
Current Trends
in the
Embryology of Angiosperms
Edited by
S.S. Bhojwani
University of D elhi,
Delhi, India
and
W.Y. Soh
Chonbruk National University,
Chonju, Republic of Korea
SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.
A c.l.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-90-481-5679-5 ISBN 978-94-017-1203-3 (eBook)
DOI 10.1007/978-94-017-1203-3
Printed on acid~free paper
All Rights Reserved
© 2001 Springer Science+Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 2001
Softcover reprint of the hardcover Ist edition 2001
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
încludîng photocopying, recordîng or by any înformation storage and
retrieval system, without written permission from the copyright owner.
CONTENTS
INTRODUCTION vii
1. MALE GAMETOGENESIS 1
Development and Structure ofS perm
DARLENE SOUTHWORTH and SCOTT D. RUSSELL
2. SPERM AND GENERATIVE CELL 17
Isolation and Manipulation
DARLENE SOUTHWORTH
3. POLLEN GERMINATION AND POLLEN TUBE GROWTH 33
Tip Growth Mechanism in Sexual Plant Reproduction
A. MOSCATELLI and M. CREST!
4. FEMALE GAMETOGENESIS 67
Ontogenesis oft he Embryo Sac and Female Gametes
SCOTT D. RUSSELL
5. EMBRYO SAC 89
Isolation and Manipulation
DAVID D. CASS and JOHN D. LAURIE
6. IN VIVO FERTILIZATION 101
TATYANAB. BATYGINAandVALENTINAE. VASILYEVA
7. IN VITRO FERTILIZATION 143
E. KRANZ
8. SEXUAL INCOMPATIBILITY 167
F. CRUZ-GARCIA and B.A. MCCLURE
9. ZYGOTIC EMBRYOGENESIS 197
Structural Aspects
ROMAN A CZAPIK and ROMAN A lZMAILOW
10. ZYGOTIC EMBRYOGENESIS 223
Hormonal Control ofE mbryo Development
B. FISCHER-IGLESIAS and G. NEUHAUS
11. ZYGOTIC EMBRYOGENESIS : DEVELOPMENTAL GENETICS 249
The Formation ofa n Embryo from a Fertilized Egg
KA THRIN SCHRICK and THOMAS LAUX
12. SOMATIC EMBRYOGENESIS 279
TREVOR A. THORPE and CLAUDIO STASOLLA
v
Vl Contents
13. SYNTHETIC SEEDS OF ASPARAGUS OFFICINALISL. 337
KANJI MAMIYA , YUH SAKAMOTO, NOBORU ONISHI and TAKA YA SU HIROSA WA
14. ENDOSPERM DEVELOPMENT 353
P.W. BECRAFT, R.C. BROWN, B.E. LEMMON, 0.-A. OLSEN and H. G. OPSAHL FERSTAD
15. SEED MATURATION, GERMINATION, AND DORMANCY 375
A. BRUCE DOWNIE
16. GAMETOPHYTIC APOMIXIS 419
A Successful Mutation oft he Female Gametogenesis
YVES SAV IDAN
17. PARTHENOCARPY 435
State oft he Art
ANGELO SPENA and GIUSEPPE LEONARDO ROTINO
18. ANDROGENESIS IN BRASSICA 451
A Model System to Study the Initiation ofP lant Embryogenesis
J.B.M. CUSTERS, J.H.G. CORDEWENER, M.A. FIERS, B.T.H. MAASSEN, M.M. VAN
LOOKEREN CAMPAGNE and C.M. LIU
19. ANDROGENESIS IN CEREALS 471
SWAPANK. DATTA
20. IN VITRO GYNOGENESIS 489
SANT S. BHOJWANI and T. DENNIS THOMAS
21. INHERITANCE OF CYTOPLASMIC TRAITS-EMBRYOLOGICAL 509
PERSPECTIVES
T. KUROIW A, H. KUROIWA, S. MIYAGISHIMA andY. NISHIMURA
SUBJECT AND PLANT INDEX 525
INTRODUCTION
Embryo, the progenitor of the next generation, is endowed with the unique
capacity to withstand extreme desiccation and other environmental stresses
without losing its viability and sprouts into a new plant under favourable
conditions. Several floral structures and intricate processes are involved in
the formation of embryo. These include the formation of haploid gametes
inside the male (anther) and female (ovary) sex organs, fusion of the gametes
of opposite sexes and the development of embryo (embryogenesis) and the
nutritive (endosperm) and protective (seed-coat and fruit wall) structures.
The sexual cycle in angiosperms has several unique features. For
considerable time breeders have attempted, more often unsuccessfully than
successfully, to manipulate the embryological processes to achieve their goal
of creating improved varieties of plants with new genes.
In his classic book, "An Introduction to the Embryology of
Angiosperms", published in 1950, P. Maheshwari described in detail the
development of male and female gametes, fertilization, embryo and
endosperm development, polyembryony and the range of variation in these
processes among the angiosperms. He also introduced the then emerging
field of experimental embryology. During the last 50 years a huge arsenal of
new techniques of electron microscopy, biochemistry, molecular biology,
immunology, 3-D computer reconstruction, genetics and genetic engineering
has been applied to understand finer details of the various structures and
processes associated with embryo development, and considerable new data
has been generated.
Arabidopsis thaliana has emerged as a model system to study
developmental genetics of zygotic embryogenesis (Chapter 11 ). Several
mutants defective in embryo development have been isolated, and some
embryo specific and embryo enhanced genes have been cloned. Embryo
culture, which has been used to produce rare hybrids by embryo rescue for
almost a century, is now being used to understand the physiology and
biochemistry of embryogenesis (Chapter 10 ). To have a full appreciation of
these modem areas of embryogenesis, it is important to have a good
understanding of structural aspects of normal embryogenesis (Chapter 9).
A better understanding of the embryological processes has enhanced our
manipulative power to overcome the evolutionary barriers to crossability
(Chapter 8). A major breakthrough in the field of experimental embryology
during the last decade has been the development of reliable methods to
isolate live male (Chapters 1, 2) and female (Chapters 4, 5) gametes, their
fusion and culture of in vitro produced zygotes to obtain fertile plants
(Chapter 7). With the availability of a reasonable numbers of viable naked
gametes a host of basic aspects of gametic recognition and fusion are being
investigated. These cells have also given a better understanding of the
structure of the gametes. A new concept emerged from the research on
vii
Vlll Introduction
sperm isolation is of "male germ unit", which suggests that the fate of the
two sperms in double fertilization is probably pre-determined.
An entirely new field of Experimental Embryology has emerged.
Formation of asexual embryos from somatic and gametic cells in tissue
cultures has put to rest the myths that the egg holds the monopoly to form
embryo, and that the embryo sac is a magic bath with a unique environment
necessary for embryo development. Formation of embryos by single somatic
cells and unicellular haploid microspores, under highly controlled
conditions, are proving to be excellent systems to study the physiology,
biochemistry and genetic control of embryogenesis in angiosperms, which
was not possible earlier due to the inaccessibility of the zygotic embryo,
seated under several layers of ovarian and ovular tissues. A large number of
somatic embryos of different stages can be collected by fractionation for
biochemical studies. Therefore, considerable attention is being paid to
achieve controlled, synchronized development of somatic embryos.
Considerable new information on induction, development, maturation and
germination of somatic embryos has already become available (Chapter 12).
Somatic embryogenesis is also looked upon as the future method of large
scale clonal propagation of superior and genetically engineered crops,
particularly woody perennials. To facilitate their direct field planting, somatic
embryos are being manipulated to develop Synthetic Seeds (Chapter 13).
Induction of male (androgenesis; Chapters 18, 19) and female
(Gynogenesis; Chapter 20) gametes to develop into sporophytes independent
of fertilization has opened up a new approach to plant breeding. Haploids
can be used to produce homozygous plants in a single step, thus cutting
down the breeding time to almost half. Several new varieties of crop plants
developed with the aid of androgenesis have been commercialized. Haploids
have many other applications. The possibility to change the fate of a
unicellular, haploid microspore from gametophytic development to
sporophytic development by a single physical treatment (e.g., high
temperature shock, starvation) has made it an excellent system to understand
the process of induction of embryogenesis (Chapter 18).
The embryological processes are also being subjected to genetic
manipulation. For example, eggplant has been engineered to produce
parthenocarpic fruits (Chapter 17). There is renewed interest in
understanding the mechanism of Apomixis (Chapter 16) because of its
potential role in clonal propagation of large volume agronomic crops, such
as rice. Recent embryological studies are providing some new insight into
the mechanism of cytoplasmic inheritance (Chapter 21).
The progress in embryological research during the last two decades has
been so impressive that full issues of some journals have been devoted to
reproductive biology of angiosperms. Books have been published on specific
aspects of the embryology of angiosperms, such as Apomixis,
Embryogenesis, Embryo Nutrition, Pollen Biology, Sexual Incompatibility
Introduction ix
and Somatic Embryogenesis. However, a book with up-to-date chapters on
all aspects of the embryology of angiosperms, written by experts in the field
is lacking. The last book published with this objective is "The Embryology
of Angiosperms", edited by Professor B.M. Johri in 1984. Since then, the
trends in this fascinating area of research have considerably changed and the
progress has been revolutionary, justifying the publication of this volume.
The book includes 21 chapters written by scientists who have made
substantial contributions to their respective areas. The chapters are illustrated
with self-explanatory diagrams, pictures and/or flow charts. The students of
plant sciences and researchers in the areas of Plant physiology, Growth and
development, biochemistry and genetics would find it very useful. Besides a
critical review of up-to-date literature on the subject, the authors have
projected the future lines of research in their respective areas.
We are very grateful to all the authors who extended their full co
operation to us in submitting the manuscripts in time and promptly returning
the edited copies of their chapter. This enabled us to complete the book by
the date committed to the publishers.
We would like to thank profusely our students, particularly, Pradeep,
Nidhi, Rekha and Anupam for their ready help in various ways.
Sant Saran Bhojwani
Woong-Young Soh
Editors
Chapter 1
MALE GAMETOGENESIS
Development and Structure ofS perm
DARLENE SOUTHWORTH1 and SCOTT RUSSELL 2
1D epartment ofB iology, Southern Oregon University, 1250 Siskiyou Blvd., Ashland, OR
97520 and2Department ofB otany and Microbiology, University of Oklahoma, Norman, OK
73019, U.S.A.
1. Introduction
The full range of gene expression leading to male gamete formation in
flowering plants begins with determination of the stamen whorl in flower
development and ends with release of mature sperm into the embryo sac near
the egg and central cell. In this review we focus on events within the anther
from meiosis to anthesis and follow the development of sperm to their
discharge into the embryo sac. Chapter 3 in this volume covers pollen tube
growth. Here we review the principles of microsporogenesis gleaned from
ultrastructural work several decades ago (Heslop-Harrison, 1968, 1971) and
then describe recent advances and new approaches to male gametogenesis.
1.1. OVERVIEW OF MALE GAMETOGENESIS
In anthers of very young flower buds, a column of microsporocytes
(colloquially called pollen mother cells) is formed in the center of the future
anther sac. With the completion of meiosis, pollen mother cells produce
haploid microspores (typically four per microsporocyte) that differentiate
into pollen (Bedinger, 1992). Microspores develop a complex cell wall, take
up nutrients, and differentiate. Each haploid cell divides asymmetrically into
a larger vegetative cell and a smaller generative cell, both enclosed within
the pollen grain wall. The vegetative cell will not divide again, but will
develop a long extension that is the pollen tube. The generative cell divides
S.S. Bhojwani and W.Y. Soh (eds.), Current Trends in the Embryology ofA ngiosperms, 1-16.
© 2001 Kluwer Academic Publishers.
2 Chapter 1
either in the pollen grain or in the pollen tube to form two sperm cells.
Development of pollen is supported by the tapetum; ablation of tapetal cells
interrupts pollen maturation (Mariani et al., 1990). Recent reviews have
emphasized diverse aspects of male gametogenesis: an overview of
gametogenesis and fertilization (Southworth, 1996), the cytoskeleton of
sperm and generative cells (Palevitz and Tiezzi, 1992), association of two
sperm cells with the vegetative nucleus in the male germ unit (Mogensen,
1992), and gene expression in the developing male gametophyte
(Mascarenhas, 1989; Twell, 1994).
2. Microsporogenesis
2.1. MEIOSIS
Microsporocytes are encased in a special callose wall so that after meiosis,
the four haploid microspores are held together (Fig. IA). At the completion
of meiosis, microtubules radiate from telophase nuclei (Brown and Lemmon
1991, 1992a,b; Pickett-Heaps et al., 1999). This system of microtubules
creates nuclear-cytoplasmic domains that were initially interpreted as
spindles (Heslop-Harrison, 1971). However, their formation between non
sister nuclei makes this interpretation incorrect. The intersection of radiating
microtubules, including those from non-sister nuclei, determines the location
of phragmoplasts creating the cell walls that delineate individual pollen
grams.
Haploid gene expression in the microspore is extensive (Twell, 1994).
One gene expressed in tapetum and in microspores, Bcpl, is essential for
pollen development (Xu et al., 1995). Linker histones have been shown in
transgenic tobacco to be essential for normal meiosis and for pollen
development (Prymakowska-Bosak et al., 1999).
2.2. EXINE AND INTINE DEVELOPMENT
The exine is patterned on microspore plasma membrane surfaces within the
callose wall (Fig. lA-G) (for reviews see Heslop-Harrison, 1968, 1971). A
primexine matrix is deposited between the microspore plasma membrane
and the encasing callose wall (Fig. 1A, E, F). Within this matrix, sites of
condensation of unknown substances create depressions ("crypts") in the
plasma membrane (Fitzgerald and Knox, 1995). Subsequently, on plasma
membrane peaks, pro bacula appear as the first evidence of exine components
(Fig. 1 F, G). After the callose wall is hydrolyzed, sporopollenin is deposited
from the tapetum onto the thickening exine, but by this time, the pattern is
already established (Fig. 1H). Following exine formation, the intine, a
glycan cell wall, forms from within the microspore. In spite of detailed