Photosynthetic properties of two different soybean suspension cultures

The photosynthetic properties of two commonly used suspension cultured line s, embryogenic and photoautotrophic (PA, SB-l line) cells of soybean [Glyci ne max (L.) Merr.] were characterized. We found that compared to the dark g reen PA cells, the light green embryogenic cells contained fewer and smalle r plastids with less-developed thylakoid membranes. The embryogenic cells a lso contained much lower contents of both chlorophyll and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) protein, an undetectable level of Rubisco small subunit protein, and a Very low rate of photosynthesis. While the DNA contents of the nuclear genomes were similar in these two types of cultured cells, the embryogenic cells po ssessed a markedly lower content of plastid DNA. The 18-year-old PA suspens ion culture, SB-1, continues to evolve with higher Rubisco and plastid DNA contents than leaves, and with small decreases in nuclear DNA content that appears to mimic changes in chromosome numbers. These findings may prove us eful in the application of plastid transformation, particularly when non-le af or non-green tissues must be used as targets for transformation and plan t regeneration.