OrMKK3 Influences Morphology and Grain Size in Rice

Area of Science:

• Plant Molecular Biology
• Crop Genetics
• Agricultural Science

Background:

• Rice morphology and grain size are critical for crop yield, yet the genetic basis for natural variations remains largely unknown.
• Mitogen-activated protein kinases (MAPKs) play diverse roles in plant development, but their specific functions in regulating rice grain characteristics are not fully elucidated.

Purpose of the Study:

• To identify and characterize novel genes involved in regulating rice morphology and grain size.
• To investigate the function of mitogen-activated protein kinase 3 (OrMKK3) from *Oryza officinalis* and its role in rice development.

Main Methods:

• Characterization of *OrMKK3* gene and its alternative splicing variants.
• Subcellular localization studies using Green fluorescent protein (GFP)-*OrMKK3* fusion proteins in rice protoplasts.
• Gene expression analysis of grain size-related genes following *OrMKK3* overexpression.
• Phylogenetic analysis of *OrMKK3* across different rice varieties.
• Assessment of *OrMKK3*'s influence on brassinosteroid (BR) responses and related gene expression.

Main Results:

• *OrMKK3* exhibits alternative splicing and its fusion protein localizes to the cell membrane and nucleus.
• Overexpression of *OrMKK3* significantly impacts the expression of genes associated with grain size, including *SMG1*, *GW8*, *GL3*, *GW2*, and *DEP3*.
• Phylogenetic analysis reveals conservation of *OrMKK3* in plants, with notable variations among *indica*, *japonica*, and wild rice subspecies.
• A slight influence of *OrMKK3* on brassinosteroid (BR) responses and BR-related gene expression was observed.

Conclusions:

• *OrMKK3* is identified as a novel gene influencing rice morphology and grain size.
• The findings suggest a potential link between mitogen-activated protein kinase signaling and brassinosteroid pathways in regulating grain development.
• Understanding *OrMKK3*'s function provides new targets for improving rice yield through genetic manipulation.