Vicilin and legumin storage proteins are abundant in water and alkali soluble protein fractions of glandless cottonseed

Authors: He, Zhongqi; Mattison, Chris; Zhang, Dunhua; Grimm, Casey

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2021
Publication Date: 4/28/2021
Publication URL: https://handle.nal.usda.gov/10113/7709531
Citation: He, Z., Mattison, C.P., Zhang, D., Grimm, C. 2021. Vicilin and legumin storage proteins are abundant in water and alkali soluble protein fractions of glandless cottonseed. Scientific Reports. 11. Article 9209. https://doi.org/10.1038/s41598-021-88527-7.
DOI: https://doi.org/10.1038/s41598-021-88527-7

Interpretive Summary: Cotton plant is an economically important crop that is known for fiber, cottonseed oil and protein content 1-3. Cottonseed protein comprises multiple polypeptides (i.e., various protein fractions) including seed storage proteins and proteins with other biological functions. The traditional variety of cottonseed contains the toxic chemical gossypol and is labeled “glanded (Gd) cottonseed” as gossypol is deposited in scattered tissue structures called glands. Research efforts have been made to produce a new type of “glandless” (Gl) cottonseed in which there is only trace gossypol content present. In this work, we isolated and separated Gl cottonseed proteins into water- and alkali-soluble fractions, analyzed their polypeptide profiles, and compared them to the peptide features of Gd cottonseed protein fractions. While the majority of proteins were vicilin and legumin storage proteins, other functional and function-unknown proteins or their fragments were also detected. This work enriched the fundamental knowledge of Gl cottonseed protein composition, and will be helpful in better understanding the functional and physicochemical properties of Gl cottonseed protein.

Technical Abstract: The traditional variety of cottonseed contains the toxic terpenoid gossypol and is labeled “glanded cottonseed” as gossypol is deposited in scattered tissue structures called glands. Research efforts have been made to produce a new type of “glandless” cottonseed in which there is only trace gossypol content. Previous work has reported the protein profile of glanded cottonseed protein, but glandless cottonseed protein has not been characterized. In this work, we sequentially extracted water (CSPw)- and alkali (CSPa)-soluble protein fractions from glandless cottonseed. SDS-Gel electrophoresis separated CSPw and CSPa to 8 and 14 dominant protein bands, respectively. Liquid chromatography-electrospray ionization-tandem spectrometry identified peptide fragments of 336 proteins. While the majority of peptides were matched to vicilin and legumin storage proteins, peptides from other functional and uncharacterized proteins were also detected. Compared to glanded samples, we found lower levels (abundance) and types of legumin isoforms, but higher levels and more fragments of vicilin-like antimicrobial peptides in glandless samples. Differences in peptide fragment patterns of 2S albumin and oleosin were also observed between glandless and glanded protein samples. These differences might be due to the higher extraction recovery of proteins from glandless cottonseed as proteins from glanded cottonseed tended to be bound with gossypol, reducing extraction efficiency. The observed differences may also be due in part to an inherent mechanism to offset the gossypol’s beneficial antimicrobial properties of glandless cottonseed. This work enriches the fundamental knowledge of glandless cottonseed protein composition. For practical applications, these peptide information will be helpful in better understanding the functional and physicochemical properties of glandless cottonseed protein, and improving their food application potentials.