Genome-wide transcriptome profiling indicates the putative mechanism underlying enhanced grain size in a wheat mutant

Area of Science:

• Plant genetics and molecular biology
• Crop science and breeding
• Agricultural biotechnology

Background:

• Grain size and weight are critical determinants of crop yield.
• Endogenous brassinosteroids (BRs) are key regulators of plant growth, including grain development.
• Understanding genetic factors influencing grain composition is vital for crop improvement.

Purpose of the Study:

• To investigate the genetic basis of increased grain size in a novel wheat mutant, SM482gs.
• To elucidate the role of brassinosteroids (BRs) in regulating grain size, weight, and composition.
• To analyze differential gene expression related to BR biosynthesis, signal transduction, and nutrient accumulation.

Main Methods:

• Identification and phenotypic characterization of an ethyl methylsulfonate (EMS) induced mutant wheat line (SM482gs) with altered grain traits.
• Comparative transcriptomic analysis of SM482gs and wild-type (WT) wheat at four developmental stages (9, 15, 20, and 25 days post-anthesis).
• Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to identify differentially expressed genes (DEGs) and regulatory networks.

Main Results:

• The SM482gs mutant displayed significantly increased grain size, 1000-grain weight, and protein content, but reduced starch content compared to WT.
• Transcriptomic analysis revealed differential expression of numerous genes, with eight BR biosynthesis and signal transduction genes significantly upregulated in SM482gs.
• Expression of seed storage protein (SSP)-encoding genes was upregulated, while starch synthase genes showed decreased expression in the mutant, correlating with altered grain composition.

Conclusions:

• Enhanced brassinosteroid (BR) signaling in the SM482gs mutant likely contributes to its increased grain size and weight through complex network interactions.
• Altered expression of starch synthase and seed storage protein genes in SM482gs directly impacts grain composition, leading to higher protein and lower starch content.
• This study provides insights into the molecular mechanisms underlying grain development and composition, offering potential targets for wheat breeding programs.