A Sorghum Mutant Resource as an Efficient Platform for Gene Discovery in Grasses

Abstract

Sorghum (Sorghum bicolor) is a versatile C4 crop and a model for research in family Poaceae. High-quality genome sequence is available for the elite inbred line BTx623, but functional validation of genes remains challenging due to the limited genomic and germplasm resources available for comprehensive analysis of induced mutations. In this study, we generated 6400 pedigreed M4 mutant pools from EMS-mutagenized BTx623 seeds through single-seed descent. Whole-genome sequencing of 256 phenotyped mutant lines revealed >1.8 million canonical EMS-induced mutations, affecting >95% of genes in the sorghum genome. The vast majority (97.5%) of the induced mutations were distinct from natural variations. To demonstrate the utility of the sequenced sorghum mutant resource, we performed reverse genetics to identify eight genes potentially affecting drought tolerance, three of which had allelic mutations and two of which exhibited exact cosegregation with the phenotype of interest. Our results establish that a large-scale resource of sequenced pedigreed mutants provides an efficient platform for functional validation of genes in sorghum, thereby accelerating sorghum breeding. Moreover, findings made in sorghum could be readily translated to other members of the Poaceae via integrated genomics approaches.

Highly efficient de novo mutant identification in a Sorghum bicolor TILLING population using the ComSeq approach

“…DNA was extracted from a pool of 12 sprouting M 4 seeds (Experimental procedures), which were advanced by pooling 10 M 3 panicles, and thus lines are expected to contain more heterozygous mutations than homozygous mutations. Whole-genome sequencing indicated a ratio of more than 4.2:1 heterozygous to homozygous SNPs across the entire genome (Jiao and Burke, 2016), consistent with our findings.…”

Genome-wide association analysis of seedling traits in diverse Sorghum germplasm under thermal stress

“…Fortuitously, EMS-induced mutants for Sb06g025040 and Sb03g012930 genes from the above network are available from sorghum mutant library [60] for evaluation. Briefly, the ARS207 mutant line had non-synonymous mutation in Sb06g025040 , and the ARS137 mutant had a non-synonymous mutation in Sb03g012930 [60]. We performed expression analysis on these mutants to determine their effect on gene expression.…”

Registration of BTx623ms8, a New and Easily Identifiable Nuclear Male Sterile Mutant in Sorghum

“…We found only 203 EMS‐induced mutations (single nucleotide polymorphisms) in ms8 that were different from the wild‐type BTx623. From the 256 mutant lines sequenced, the average number of mutations per line was 7660 (Jiao et al, 2016). Statistically, each backcross can remove 50% of the unlinked mutations.…”