Identification of variant α‐kafirin alleles associated with protein digestibility in grain sorghum

Abstract

Owing to its unique adaptation to challenging environments, sorghum [Sorghum bicolor (L.) Moench] 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. 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 present study was to investigate the impact of DNA sequence variations in genes coding for sorghum seed storage proteins (kafirins) on protein digestibility of sorghum grain. The entire kafirin gene family of 27 genes and six 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. A pooled DNA library was prepared and deeply sequenced using the 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 α‐kafirin alleles, all located on chromosome 5, were strongly associated with protein digestibility. Three of the alleles were linked to high digestibility and one to low digestibility. These variants overlap with the genes, Sobic.005G185600, Sobic.005G188800, Sobic.005G189000 (high digestibility alleles), and Sobic.005G192801 (low digestibility allele). In silico predictive analysis showed the variants cause missense change in the amino acid sequences of the corresponding proteins. Molecular markers linked to these variant alleles may serve as breeding tools for genetic improvement of protein digestibility in sorghum.

Harnessing Sorghum Landraces to Breed High-Yielding, Grain Mold-Tolerant Cultivars With High Protein for Drought-Prone Environments

“…One nutritional constraint to the use of sorghum as food is the poor digestibility of sorghum proteins in cooking (Tesso et al, 2008 ). Duressa et al ( 2020 ) have reported sorghum accessions with a protein content as high as 15% but with different digestibility percentages (a measure of the susceptibility of protein to proteolysis). For example, the sorghum accession SC663 with a protein content of 15.5% had a high protein digestibility of 70.77%.…”

RNAi-Mutants of Sorghum bicolor (L.) Moench with Improved Digestibility of Seed Storage Proteins

“…To solve the problem of poor digestibility of kafirins various genetic and biotechnological approaches may be used: experimental induction of mutants with impaired synthesis or altered amino acid composition of kafirins [15]; identification of naturally occurring allelic variants of kafirins [16][17][18][19]; obtaining transgenic plants with the genetic constructs that induce silencing of γ-and/or α-kafirin genes [20][21][22][23]; editing the nucleotide sequences of kafirin genes in order to obtain lines with complete or partial knockout of these genes [24].…”

Wuschel2 enables highly efficient CRISPR/Cas-targeted genome editing during rapid de novo shoot regeneration in sorghum

“…1k ). In the second experiment, dropout a segment of the Kaf ( γ-Kafirin, Sobic.002G211700 ) gene 30 was tested using two sgRNAs ( Sb-Kaf-CR1 and -CR3 ) (Supplementary Fig. 4 ) in Tx430.…”