Somatic embryogenesis from Sorghum bicolor leaves

Abstract

Plant regeneration from totipotent cultured cells or protoplasts is a prerequisite for the often proposed genetic modification of plants through somatic cell genetics, and has been achieved in many species. The cereals (and the rest of the Gramineae) have, however, proved to be extremely unresponsive to in vitro culture techniques¹. The most convenient source of plant protoplasts is the leaf tissue because it allows the isolation of a large, relatively uniform cell population without the necessity of killing the plant. However, despite considerable efforts, sustained cell division has never been obtained from cereal leaf blade protoplasts². Thus, a crucial question arises of whether leaf cells from cereals are actually totipotent and consequently, whether they can be useful for somatic cell genetics. We now report that young leaf tissue of a cereal can express totipotency even to the extent of forming somatic embryos. However, the ability to respond is rapidly lost during leaf maturation. We think that this phenomenon can explain many difficulties faced in cereal tissue culture. Moreover, the leaf culture we describe may help to ascertain whether mature cereal cells are merely no longer competent (in the sense of Halperin³) to respond to tested in vitro conditions or whether they actually lose their totipotency.