Annals of Botany

How to suck eggs

Mention of in vitro fertilization often leads us to think of ‘test-tube babies’. Since its inception in 1978 this technique has indeed helped tens of thousands of subfertile couples to have children. It has also been used in studies of fertilization and, in non-human mammals, for genetic manipulation by inserting an exogenous gene into the newly fertilized egg or zygote. However, it will surprise many people that IVF has also been achieved for plants and has been used as a tool to study fertilization processes. Genetic manipulation of zygotes, created either by IVF or by isolation after in vivo fertilization, have both been successful in plants. Further, IVF techniques also have a potential for creating new hybrids by allowing gametes to interact directly, bypassing stigmatic or stylar barriers to fertilization. Unfortunately, the range of species from which egg cells and/or zygotes have been isolated is small but this has now been extended to Alstroemeria aurea by Hoshino et al. (Sapporo, Japan, pp. 1139–1144). Their aim has been to use IVF to achieve interspecific hybridization in this genus, widely used as ornamentals. The initial approach to isolation of egg cells and zygotes was to dissect out of the ovules (with or without prior pollination, depending on whether zygotes were required), incubate the ovules in a solution of cell-wall degrading enzymes, followed by microdissection with hand-made glass needles. It was found that excision of the chalazal region of the ovule strongly promoted helpful enzymic digestion of the sporophytic tissue surrounding the embryo sac. A further innovation was the use of a specially designed computer-controlled micropump, connected by fine-bore tubes to microcapillaries into which egg cells or zygotes could be sucked after removal from the ovules. Egg cells and zygotes isolated in this way were viable as indicated by vital staining, raising hopes for the use of these techniques in breeding improved strains of Alstroemeria species.

Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk