Quantitative comparison of the storage protein distribution in glandless and glanded cottonseeds

Glanded (Gd) cottonseed (Gossypium hirsutum L.) contains scattered gossypol glands. Glandless (Gl) cottonseed is a new type of seed containing only trace levels of gossypol. This work quantitatively compared the content and migration pattern of Gd and Gl protein isolates. Both protein samples were subjected to sodium dodecyl sulfate (SDS)-gel electrophoresis, and the protein gel bands were separated into seven partitions for peptide mass spectroscopic analysis. While multiple peptide fragments (isoformers) of vicilin and legumin proteins were present in both samples, the percentage of vicilins in total seed protein was higher in Gd (74.9%) than in Gl (63.4%). In contrast, legumin proteins were more abundant in Gl (30.4%) than Gd (23.6%). Minor protein components such as lipid-related oleosins and vicilin-like antimicrobial peptides 2-2 were also observed at a relatively higher incidence in Gl compared with Gd, potentially reflecting a need for increased protein-related defense capability in the absence of gossypol against natural predators or adverse growth environment.