An Ethyl Methanesulfonate-Induced GIF1 Splicing Site Mutation in Sesame Is Associated with Floral Malformation and Small Seed Size

Flower and inflorescence architecture play fundamental roles in crop seed formation and final yield. Sesame is an ancient oilseed crop. Exploring the genetic mechanisms of inflorescence architecture and developmental characteristics is necessary for high-yield breeding improvements for sesame and other crops. In this study, we performed a genetic analysis of the sesame mutant <i>css1</i> with a malformed corolla and small seed size that was mutagenized by ethyl methanesulfonate (EMS) from the cultivar Yuzhi 11. Inheritance analysis of the cross derived from <i>css1</i> mutant × Yuzhi 11 indicated that the mutant traits were controlled by a single recessive gene. Based on the genome resequencing of 48 F₂ individuals and a genome-wide association study, we determined SNP9_15914090 with the lowest <i>p</i> value was associated with the split corolla and small seed size traits, which target gene <i>Sigif1</i> (<i>GRF-Interacting Factor 1</i>)<i>. SiGIF1</i> contains four exons and encodes a coactivating transcription factor. Compared to the wild-type allelic gene <i>SiGIF1</i>, <i>Sigif1</i> in the mutant <i>css1</i> has a splice donor variant at the exon2 and intron2 junction, which results in incorrect transcript splicing with a 13 bp deletion in exon2. The expression profile indicated that <i>SiGIF1</i> was highly expressed in the flower, ovary, and capsule but lowly expressed in the root, stem, and leaf tissues of the control. In summary, we identified a gene, <i>SiGIF1</i>, that regulates flower organs and seed size in sesame, which provides a molecular and genetic foundation for the high-yield breeding of sesame and other crops.