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ekranz@botanik.uni-hamburg.de  Phone ++49 40 42816 227  Fax     ++49 40 42816 229  s.scholten@botanik.uni-hamburg.de  Phone ++49 40 42816 309  Fax     ++49 40 42816 229   Guest scientist: Dr. Takashi Okamoto, Tokyo Metropolitan University

 Angiosperm Fertilization,  Embryo and Endosperm Development
 

• In Vitro Fertilization
• Zygote, Embryo and Endosperm Development
• Gene Expression in Gametes and Zygotes

 

In Vitro Fertilization The application of micromanipulation techniques enables the isolation and in vitro fusion of male and female angiosperm gametes. Because of access to single gametes and zygotes, these tools facilitate studies of gamete interaction, of gametic hybridization and of early, fertilization-induced developmental processes.

Zygote, Embryo and Endosperm Development in Vitro In combination with tissue culture methods, which are adapted for the culture of single cells, these techniques allow individual development of isolated and of in vitro-produced zygotes as well as of in vitro- produced endosperm. Both in vitro- produced zygotes and zygotes which are isolated after in vivo pollination develop into embryos and fertile plants in culture. Two-celled embryo (A) and transition stage embryo (B) from cultured in vitro-ferilized maize egg cells.	A	C
Also in maize, in vitro-produced primary endosperm cells (C) develop into endosperm (D) in culture. Zygotes and endosperm are able to self-organize in culture independently from maternal tissue. Many steps of early development in vitro of both the embryo and endosperm are comparable to the situation in planta, making this system a useful model for studies of embryogenesis and endosperm development.	B	D

Gene Expression in Gametes and Zygotes

The use of these techniques together with biochemical and molecular methods, adapted to
the analysis of single cells, allows one to analyse early developmental events, precisely timed
after fertilization. We apply transgene technology to the in vitro fertilization system to express
foreign genes and to alter gene expression in early stages of development. Expression of
green-fluorescence-protein (GFP) was found

(1) in zygotes after delivery of a GFP-construct via microinjection,  (2) in synergids, egg and central cells of stable transformed plants and  (3) in zygotes after in vitro fertilization with transgenic sperm cells.

By use of inducible expression of transgenes we intend to characterize zygote and primary
endosperm cell development and to study the function of developmentally regulated genes
involved in processes occurring soon after fertilization.

Representative Reviews

Kranz, E. (2001). In Vitro Fertilization.
In: Current trends in the Embryology of Angiosperms, eds.
S.S. Bhojwani and Soh, W. Y., Kluwer: Dordrecht. Pp. 143-166.
Kranz, E., Kumlehn, J. and Dresselhaus, T. (1999). Fertilization and zygotic embryo development in vitro.
In: Fertilization in Higher Plants, eds. M. Cresti, G. Cai and A. Moscatelli, Springer: Berlin, Heidelberg.
Pp. 337-349.
Kranz, E. and Kumlehn J. (1999). Angiosperm fertilization, embryo and endosperm development in vitro.
Plant Sci. 142, 183-197.
Kranz, E., Petra von Wiegen, Hartmut Quader, and Horst Lörz (1999). Central cell fertilization and
endosperm development in vitro. http://www.biologie.uni-hamburg.de/b-online/kranz/St-Louis.htm
Kranz, E. and Dresselhaus, T. (1996). In vitro fertilization with isolated higher plant gametes.
Trends in Plant Science 1, 82-89.

Representative Publications
Scholten, S., Lörz, H. and Kranz, E. (2002). Paternal mRNA and protein synthesis coincides with male chromatin decondensation in maize zygotes. Plant J. 32, 221-231.
Scholten, S. and Kranz, E. (2001). In vitro fertilization and expression of transgenes in gametes and zygotes.
Sex. Plant Reprod. 14, 35-40.
Sauter, M., von Wiegen, P., Lörz, H., and Kranz, E. (1998). Cell cycle regulatory genes from maize are
differentially controlled during fertilization and first embryonic cell division. Sex. Plant Reprod. 11, 41-48.
Kranz, E. von Wiegen, P., Quader, H. and Lörz, H. (1998). Endosperm development after fusion
of isolated, single maize sperm and central cells in vitro. Plant Cell 10, 511-524.
Kranz, E., Von Wiegen, P. and Lörz, H. (1995). Early cytological events after induction of cell division in egg cells and zygote development following in vitro fertilization with angiosperm gametes. Plant J. 8, 9-23.
Kranz, E. and Lörz, H. (1993). In vitro fertilization with isolated, single gametes results in zygotic embryogenesis and fertile maize plants. Plant Cell 5, 739-746.
Faure, J.-E., Mogensen, H.L., Dumas, C., Lörz, H. and Kranz, E. (1993). Karyogamy after electrofusion of single egg and sperm cell protoplasts from maize: Cytological evidence and time course. Plant Cell 5, 747-755.
Kranz, E. (1993). In vitro Befruchtung mit einzelnen isolierten Gameten von Mais (Zea mays L.). Habilitationsschrift. Universität Hamburg.
Dresselhaus, T., Lörz, H. and Kranz, E. (1994). Representative cDNA libraries from few plant cells. Plant J. 5, 605-610.
Kranz, E. and Lörz, H. (1994). In vitro fertilization of maize by single egg and sperm cell protoplasts fusion mediated by high calcium and high pH. Zygote 2, 125-128.
Kranz, E., Bautor, J. and Lörz, H. (1991). In vitro fertilization of single, isolated gametes of maize mediated by electrofusion. Sexual Plant Reproduction 4, 12-16.

Links to Related Sites on the Internet

In vitro Befruchtung mit isolierten Gameten von  Angiospermen
http://www.biologie.uni-hamburg.de/b-online/kranz/1996.htm

Endosperm development after fusion
of isolated, single maize sperm and central cells in vitro.
http://www.biologie.uni-hamburg.de/b-online/kranz/St-Louis.htm

EU-Project MAZE
http://www.amaize.org/home/homeA.html

Impressum  /  25-2-2004  /  E. Kranz  /  http://www.biologie.uni-hamburg.de/bzf/fb5a091/fb5a091a.htm	suchen