Identification of genetic variants controlling diosgenin content in Dioscorea zingiberensis tuber by genome-wide association study

Abstract

Background: Diosgenin is an important steroidal precursor renowned for its diverse medicinal uses. It is predominantly sourced from Dioscorea species, particularly Dioscorea zingiberensis. Dioscorea zingiberensis has an ability to accumulate 2-16% diosgenin in its rhizomes. In this study, a diverse population of 180 D. zingiberensis accessions was used to evaluate the genomic regions associated with diosgenin biosynthesis by the genome wide association study approach (GWAS).

Results: The whole population was characterized for diosgenin contents from tubers by gas chromatography mass spectrometry. The individuals were genotyped by the genotyping-by-sequencing approach and 10,000 high-quality SNP markers were extracted for the GWAS. The highest significant marker-trait-association was observed as an SNP transversion (G to T) on chromosome 10, with 64% phenotypic variance explained. The SNP was located in the promoter region of CYP94D144 which is a member of P450 gene family involved in the independent biosynthesis of diosgenin from cholesterol. The transcription factor (TF) binding site enrichment analysis of the promoter region of CYP94D144 revealed NAC TF as a potential regulator. The results were further validated through expression profiling by qRT-PCR, and the comparison of high and low diosgenin producing hybrids obtained from a bi-parental population.

Conclusions: This study not only enhanced the understanding of the genetic basis of diosgenin biosynthesis but also serves as a valuable reference for future genomic investigations on CYP94D144, with the aim of augmenting diosgenin production in yam tubers.

Keywords: Dioscorea Zingiberensis; Breeding; Diosgenin; Enzyme; P450.

Fig. 1

Variation of diosgenin content among the association panel at two planting sites (A) Hainan and (B) Luohe

Fig. 2

Population structure (A) and principal component (B) analyses of the D. zingiberensis accessions

Fig. 3

Genome-wide association mapping for diosgenin content in D. zingiberensis. Manhattan plot for diosgenin content (A). Quantile-quantile plot for diosgenin content (B)

Fig. 4

Characterization of the structure of D. zingiberensis CYP94D144 gene showing the location of the SNP Chr10:12542 (T/G) in the promoter region (A). Comparative quantification of diosgenin content for accessions exhibiting T and G alleles (B). Analysis of the transcription binding factors in the promoter region of CYP94D144 gene (C). *** means significant difference at p < 0.001

Fig. 5

Validation of the SNP Chr10:12542 in contrasting hybrids derived from a mapping population (A). Comparative quantification of diosgenin content in two contrasting pools of hybrids for SNP alleles and diosgenin content (B). Relative expression of the both versions of the gene via qRT-PCR experiment (C)