| A 27 kd peptide with an isoelectric point of 6.9-7.0 was associated with the induction of callus formation from excised seedling tissues and immature embryos in vitro, of Sorghum bicolor (L.) Moench. Callus formation was always preceded by production of this callus-associated peptide (CAP1), as detected by two-dimensional polyacrylamide gel electrophoresis. Regenerating roots and shoots did not synthesize CAP1, although these organs were attached to actively growing calli. CAP1 and a second callus-associated peptide, CAP2, are more abundant in callus tissue which has lost the ability to regenerate organ primordia in comparison to organogenic callus. Polyclonal antiserum developed to CAP1 was found to be reactive with both CAP1 and CAP2. Concanavalin A bound both CAP1 and CAP2, indicating the presence of glycosyl residues associated with these peptides. CAP1 has been detected at low levels in crown tissues of whole plants of cvs. NB9040 and IS3620C, and was increased in crown tissues following treatment of plants with 2,4-dichlorophenoxyacetic acid. CAP1 was not detected during a sampling of other whole-plant tissues.;Eight genotypes of sorghum were evaluated for their in vitro abilities with respect to callus initiation, dry weight and CAP1 accumulation. All parameters showed variability within and between genotypes, but statistically significant differences were found for all variables considered. Genotypes tended to remain in a general ranking with respect to all three parameters. However, cultivar 401-1 accumulated the highest dry weight values, had initiation frequencies significantly above most of the other genotypes evaluated, yet accumulated the lowest quantity of CAP1. Thus, the presence of CAP1 and the in vitro ability of this sorghum genotype, with respect to callus initiation and growth, do not appear to be positively correlated. Polyclonal antiserum raised against CAP1 from cv. NB9040 reacted with electrophoretically identical peptides from all other genotypes examined. |
