Specific proteins potentially associated with somatic embryogenesis in orchardgrass

Various biotechnological techniques studied to supplement conventional plant breeding procedures require the regeneration of whole plants from cells or tissue cultured in vitro. The objective of this study with orchardgrass (Dactylis glomerata L.) was to investigate specific protein differences associated with 'Embryogen-P', a genotype which produces somatic embryos in high numbers, and four nonembryogenic genotypes by one-and two-dimensional polyacrylamide gel electrophoresis.

Four proteins were present in Embryogen-P leaves that were not present in the leaves of the nonembryogenic genotypes. One protein appeared in the nonembryogenic genotypes that did not appear in Embryogen-P. Similar results were found in the embryogenic and nonembryogenic progeny of a cross between Embryogen-P and one of the nonembryogenic genotypes. These results support an association of specific proteins with the ability to produce somatic embryos.

Embryogenesis was supported in suspension cultures by the addition of casein hydrolysate to the medium. Five proteins were found in the protein profiles of these cultures that were not present in those not supporting embryogenesis. Similar results were obtained in a second experiment using (NH₄)₂SO₄ to support enbryogenesis. Although these proteins may not be directly involved in embryogenesis, they appear to be associated with the process.

Basal sections of Embryogen-P leaves were analyzed after 2, 4, 7, 10, 14, or 22 d after culture. A total of 12 proteins were found to be produced during culture, 9 at 7 d, 2 at 10 d, and 1 at 14 d after culture. Appearance of these proteins at different times throughout the culture period suggests a time course for their synthesis.

Leaves were placed on medium with abscisic acid (ABA) and removed at 1, 2, or 3 d after culture. Four proteins were found in leaves 1 d after culture and three were present after 2 d. Three proteins found in leaves 1 d after culture with ABA had the same molecular weights as three appearing at 7 d after culture on medium without ABA. These three may be promoted at an earlier time by ABA and produced in response to embryogenesis.