Synthesis of extracellular proteins in embryogenic and non-embryogenic cell cultures of alfalfa

Extracellular proteins, released into the culture medium from alfalfa cells grown in embryogenic and nonembryogenic conditions, were S-35-methionine labelled at different days of culture. SDS-PAGE analysis showed significant differences between the patterns of extracellular proteins secreted into the medium devoid of 2,4-D, in which cells formed somatic embryos, or in presence of 2,4-D, in which undifferentiated cell proliferation took place. Some proteins, evident in 2,4-D-supplied cultures, disappeared when cells were subcultured in the embryogenic conditions. Western analysis with antibodies against the carrot extracellular proteins EP1 and EP2 showed the presence of homologous alfalfa proteins. In 2,4-D depleted alfalfa cells, an EP1-like protein disappeared and another one was reduced, while the presence of the EP2-like protein was, in the same conditions, strongly enhanced.