The MGS1 gene in sorghum, encoding a MIKC-type MADS-box transcription factor, regulates the multiple-grain spikelet (MGS) trait, with natural mutations like mgs19E and mgs1BA45 significantly increasing grain yield by producing adjacent double-pistil primordia.

Spikelets, the fundamental units of crop inflorescences, play a crucial role in grain number. In cereals like sorghum, spikelets typically produce a single fertile floret. However, certain sorghum germplasms exhibit the multiple-grain spikelet (MGS) trait, forming two mature grains within a single spikelet. This characteristic has potential for increasing grain yield. The MGS1 gene, encoding a monocot-specific MIKC-type MADS-box transcription factor, was identified as the key regulator of this trait by scientists from the Chinese Academy of Sciences, Sun Yat-sen University, China Agricultural University, Syngenta Group China and University of Chinese Academy of Sciences. MGS1 contains four domains responsible for DNA binding, heterodimerization, and transcriptional activation. CRISPR-Cas9 knockout lines of MGS1 (MGS1KO-1 and MGS1KO-2) revealed a significant increase in double-grain spikelets, although some floral malformations reduced seed-setting rates. Phylogenetic analysis confirmed MGS1 as an ortholog of rice OsMADS32, further supporting its role in floral organ development.

Comparative RNA-seq analysis identified 165 differentially expressed genes (DEGs) enriched in transcription factor and enzyme activity pathways, implicating MADS-box family genes like SbMADS3, SbMADS13, and SbMADS16 in floral organ determinacy. Natural mutations in MGS1, including mgs19E and mgs1BA45, were found to induce the MGS phenotype by producing adjacent double-pistil primordia, increasing grain yield by up to 43.1%. Linkage analysis confirmed MGS1 as a single recessive locus. These findings provide a genetic framework for breeding high-yield sorghum varieties using MGS1 natural variations. 

 SorghumBase examples: 

Figure 1: Phylogenetic analysis of the MADS-box transcription factor SbMADS3 (SORBI_3001G314400) based on the homolog tab in SorghumBase. The gene tree illustrates the homology relationships of SbMADS3, highlighting 313 homologs, including 52 orthologs and 6 paralogs. The alignment overview shows protein sequences color-coded by InterPro domain. The authors discussed a subset of MADS-box family genes involved in floral organ determinacy that were differentially expressed, including SbMADS3 and SbMADS16, which were both downregulated, whereas SbMADS13 was upregulated in MGS1KO-2 compared with sorghum Wheatland.
Figure 2: This figure shows the expression profile of SORBI_3001G314400 (Sb01g030570, Sobic.001G314400, SbMADS3) under the Expression tab (All Studies) in the search display on SorghumBase. It displays the baseline expression of the gene across all 10 published sorghum BTx623 datasets curated and processed by EMBL-EBI Expression Atlas in collaboration with the SorghumBase team.
Figure 3: Sorghum bicolor Developmental Atlas depicting the expression profile of SbMADS3 (SORBI_3001G314400)across different developmental stages. The diagram illustrates morphological changes at 8, 24, 44, 65, and 96 days after emergence (DAE), highlighting key structures such as leaves, internodes, and reproductive organs. Expression data is based on RNA-seq analysis from various tissues, including leaf, root, stem, and reproductive structures. The color-coded heatmap indicates transcript abundance, reflecting the role of SbMADS3 in developmental transitions, particularly during floral differentiation. Data sourced from McCormick et al. (2018), The Plant Journal 93:338.

Reference:

Zhang D, Tang S, Liu F, Zhao K, Li C, Xia R, Yu F, Xie Q, Xie P. Natural variations in Multi-Grain Spikelet 1 enhance grain number in sorghum. J Integr Plant Biol. 2025 Feb 21. PMID: 39981958. doi: 10.1111/jipb.13871. Read more

Genetic Regulation of the Multiple-Grain Spikelet Trait in Sorghum: Insights into MGS1 and Its Role in Enhancing Grain Yield

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