Protein content in cassava storage root is associated with total abundance of carotenoids

Authors: CARVALHO, LUIZ - Embrapa; Anderson, James; DA SILVA, J PADILHA - Embrapa; CHEN, SONGBI - Chinese Academy Of Tropical Agricultural Sciences; DE SOUZA, CLAUDIA - Universidade Federal Do Parana

Submitted to: International Research Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2019
Publication Date: 4/1/2019
Citation: Carvalho, L.J.C.B., Anderson, J.V., Da Silva, J.P., Chen, S., De Souza, C.R.B. 2019. Protein content in cassava storage root is associated with total abundance of carotenoids. International Research Journal of Plant Science. https://doi.org/10.14303/irjps.2019.003. 10(1):1-10.
DOI: https://doi.org/10.14303/irjps.2019.003

Interpretive Summary: Protein content in Cassava Storage Root (CSR) is low but variable, and detailed characterization of this variability is missing. In this study, variation in proteins associated with the color of CSR obtained from Amazon (Brazil) landraces were evaluated. More protein was detected in intense yellow and pink colored CSR compared to white colored CSR. Of the 143 proteins associated with carotenoid complexes isolated from specialized organs (called chromoplasts) up to 30 variations were identified among different CSR color categories, which ranged in molecular weight size from 10 - 260 Kilodaltons. Specific proteins isolated from these carotenoid complexes ranged from smaller in white colored CSR to larger in yellow and pink colored CSR. Furthermore, the major carotenoids identified in the carotenoid-protein complexes of CSR were carotene and lycopene, which was also variable depending on the specific type of CSR color. This research provides a better understanding of carotenoid-protein interactions among CSR color types, and potential approaches for improving CSR pro-vitamin-A and protein content in cassava breeding programs.

Technical Abstract: Protein content in Cassava (Manihot esculenta Crantz) Storage Root (CSR) is low but variable. Detailed characterization of this variability is missing due to past inappropriate protein quantification procedures. Here we used conventional protein analytical procedures to access variation in Total Buffer Extractable Proteins (TBEPs) associated with Cassava Storage Root (CSR) color in landraces from the Amazon (Brazil). TBEPs values varied according to storage root color from 7.5 (mg/g DWt) in intense yellow landraces to less than 2 (mg/g DWt) in white CSR, an enhancement of up to 4x were detected in intense yellow compared to white CSR, represent up to 55% more protein in the bulk of CSR. Correlations of total buffer extractable proteins and total carotenoid content produced R2 values of 0.4757, 0.6849 and 0.8958 depending on the extraction procedure. Protein polymorphisms were accessed by buffer fraction, carotenoid-protein complex separation in size exclusion chromatography, and protein size separation in SDS-PAGE profile analysis. Total buffer extractable protein molecular weight varied from 10 to 260 Kda in chromoplast enriched suspensions, while purified chromoplast carotenoid-protein complex had specific protein molecular weights of 18 kDa in white CSR, 38 and 43 kDa for yellow CSR, and 23 and 58 kDa in pink CSR phenotypes. Furthermore, of the 143 protein spots observed from purified chromoplasts using 2DE, up to 30 protein spot variations were identified among the four CSR color categories. Furthermore, carotene and lycopene were the major carotenoid types present in the carotenoid-protein complexes, which was dependent on the CSR color phenotype.