are also advantageous for molecular farming because of high level of containment that they
offer relative to whole, field-grown plants and the possibility of commercially producing
recombinant proteins. Tobacco suspension culture is the most popular system so far;
however, pharmaceutical proteins have been produced in soybean (Smith et al. 2002),
tomato (Kwon et al. 2003), and rice (Shin et al. 2003) cells. So far, more than 20 pharma-
ceutical compounds have been produced in cell suspension cultures, which include anti-
bodies, interleukins, erythropoietin, human granulocyte–macrophage colony-stimulating
factor (hGM-CSF), and hepatitis B antigen (Shadwick and Doran 2005).
5.6.3 Anther/Microspore Culture
The culture of anthers or isolated micropsores to produce haploid plants is known asanther
cultureormicrospore culture. Microspore culture has developed into a powerful tool in plant
breeding. Embryos can be produced via a callus phase or be a direct recapitulation of the devel-
opmental stages characteristic of zygotic embryos (Palmer and Keller 1997) (Fig. 5.9). It
has been known that late uninucleate to early binucleate microspores are the best explants for
embryogenesis. In this case, the somatic embryos (explained in Section 5.7.2, below)
develop into haploid plants. Doubled haploids can then be produced by chromosome-doubling
techniques. Thus microspore culture enables the production of homozygous (at every locus)
plants in a relatively short period as compared to conventional breeding techniques. These
homozygous plants are useful tools in plant breeding and genetic studies. In addition,
haploidembryosare used inmutant isolation, genetransfer,studies ofstorage product biochem-
istry, and physiological aspects of embryo maturation (Palmer and Keller 1997).
5.6.4 Protoplast Culture
Protoplastscontain all the components of a plant cell except for the cell wall. Using pro-
toplasts, it is possible to regenerate whole plants from single cells and also develop somatic
Figure 5.9.Somatic embryos regenerated from an anther.5.6. CULTURE TYPES AND THEIR USES 123