Discovery of Alpha Kafirin Alleles Associated with Protein Digestibility in Grain Sorghum

Authors: DURESSA, DECHASSA - Kansas State University; Bean, Scott; St Amand, Paul; TESSO, TESFAYE - Kansas State University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2020
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1002/csc2.20198

Interpretive Summary: Sorghum is a vital food crop for millions of smallholder communities in sub-Saharan Africa and plays an important role in global food security. One key constraint undermining food and feed value of sorghum is reduced protein digestibility which has been attributed to numerous causes. The aim of the current study was to investigate the impact of variation in DNA sequences coding for the sorghum storage protein kafirin on sorghum protein digestibility. DNA sequences of four storage protein genes were found to be related to protein digestibility. Three of the sequence variants were linked to high digestibility and one was linked to low protein digestibility. The new alleles may serve as new molecular tools for genetic improvement of protein digestibility in sorghum.

Technical Abstract: Owing to its unique adaptation to challenging environments, sorghum remains a vital food security crop for millions of smallholder communities in sub-Saharan Africa. Elsewhere, the crop is used as an important feed ingredient. The entire kafirin gene family of 27 genes and 6 cysteine proteinase inhibitor genes were amplified from genetically diverse high and low digestible sorghum genotypes in order to capture allelic variants that may be responsible for differences in digestibility. Pooled DNA library was prepared and sequenced using Ion Torrent DNA sequencing system. Variant alleles were called by mapping sequencing reads to the reference sorghum genome and tested for association with sorghum protein digestibility using quantitative (linear model regression) and qualitative (chi-square test) statistical analyses. Four a-kafirin alleles, all located on chromosome five, were strongly associated with the digestibility trait. Three of the alleles were linked to high digestibility and one to low digestibility. These variants overlap with the genes, SORBI_3005G185600, SORBI_3005G188800, SORBI_3005G189000 (high digestibility alleles), and SORBI_3005G192801(low digestibility allele). In silico predictive analysis showed the variants cause missense change in the amino acid sequences of the corresponding proteins. The new alleles may serve as new molecular tools for genetic improvement of protein digestibility in sorghum.