Analysis of growth in Sorghum callus cultures and association with a 27 kd peptide

A 27 Kd peptide was produced upon inducing 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 (2-D PAGE). 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. Anti-serum developed to CAP1 was found to be reactive with both CAP1 and CAP2. Concanavalin A (Con A) bound both CAP1 and CAP2, indicating the presence of glycosyl residues associated with these peptides. CAP1 has been detected in crown tissues of whole plants and was quantitatively enhanced in crown tissues following treatment of plants with 2,4-dichlorophenoxyacetic acid (2,4-D). CAP1 was not detected during a sampling of other whole plant tissues. The relationship of callus initiation frequency, callus dry weight and CAP1 accumulation was examined for eight genotypes of sorghum and is discussed.