Mediator complex subunit MED25 physically interacts with DST to regulate spikelet number in rice.

Area of Science:

• Plant Molecular Biology
• Plant Genetics
• Agricultural Science

Background:

• Grain number is a key determinant of rice yield.
• The DROUGHT AND SALT TOLERANCE (DST) transcription factor regulates grain number by controlling OsCKX2 expression.
• The precise mechanism by which DST regulates OsCKX2 remains elusive.

Purpose of the Study:

• To elucidate the regulatory mechanism of OsCKX2 expression by DST.
• To identify interacting partners of DST involved in grain number control.
• To understand the role of Mediator subunit OsMED25 in this pathway.

Main Methods:

• RNA interference (RNAi) and mutant analysis of OsMED25 in rice.
• Phenotypic characterization of panicle architecture and spikelet number.
• Genetic analysis to determine pathway interactions.
• Biochemical assays to confirm protein-protein interactions and transcriptional activity.

Main Results:

• OsMED25-RNAi and osmed25 mutants displayed enlarged panicles with increased branching and spikelet number, mirroring the dst mutant phenotype.
• Genetic studies confirmed OsMED25 functions within the DST-OsCKX2 pathway regulating spikelet number.
• Biochemical analyses demonstrated that OsMED25 physically interacts with DST at the OsCKX2 promoter.
• OsMED25 facilitates the recruitment of RNA polymerase II (Pol II) to the OsCKX2 promoter, activating its transcription.

Conclusions:

• OsMED25 acts as a coactivator for DST, mediating the transcriptional regulation of OsCKX2.
• OsMED25 bridges DST and the general transcriptional machinery (Pol II) to control OsCKX2 expression.
• This study reveals a novel role for OsMED25 in the DST-OsCKX2 regulatory module, enhancing understanding of rice yield improvement.