Abstract:
Transgenic sorghum (TG) lines with altered kafirin synthesis, particularly suppression of γ-kafirin synthesis, and
improved protein quality have been developed. The proportion of kafirin extracted with 60% tert-butyl alcohol alone was greatly
increased in the TG lines. However, the total amount of kafirin remained unchanged. Further, in the TG lines, the kafirin was much
less polymerized by disulfide bonding. There was also evidence of compensatory synthesis of other kafirin proteins. Cooked protein
digestibility was increased in the TG form, even after removal of interfering starch. The TG protein bodies were intermediate in
appearance between the normal type and the invaginated high digestibility mutants. Hence, the increased protein digestibility of
these TG lines is probably related to their lower levels of disulfide-bonded kafirin polymerization, allowing better access of proteases.
This work appears to confirm that disulfide bond formation in kafirin is responsible for the reduced protein digestibility of cooked
sorghum.
