Endosperm Cell and Organ Culture

Abstract

This chapter describes efforts to culture maize endosperm to enable direct developmental and metabolic studies of the cereal endosperm organ without the effects of the maternal plant. First, we describe production of endosperm in culture through either central cell fertilization in vitro or through isolation of embryo sacs following fertilization in vivo. These techniques have been used to culture cereal endosperm but appear to rely on use of maternal tissue in the culture to provide growth factors to stimulate endosperm development. Second, we summarize efforts aimed at the establishment of immortalized cultures of maize endosperm. Evolution of the basic protocol first reported almost 60 years ago resulted in in vitro endosperm cultures shown to be comprised of a mixture of cell types including those retaining endosperm-like characteristics. These cultures lacked organ identity, with endosperm-like cell types intermingled with undifferentiated callus-like cells. These cultures were successfully used in studies of starch as well as storage protein accumulation. Finally, we describe a recently reported system for in vitro culture of maize endosperm that preserves organ identity. These cultures have provided conclusive evidence that starchy endosperm and aleurone cell identity is position dependent without the need of further signaling from maternal tissues. Furthermore, this comparatively simple culture technique appears broadly applicable to several maize genotypes allowing for use of the large mutant collection generated in maize. With the real-time continuous accessibility of a developing cereal endosperm to perturbation and observation, it is hoped that this culture technique will be broadly useful for researchers to answer several previously intractable questions.