OsCLSY4 modulates epigenomic patterns and grain size in rice.

Area of Science:

• Plant molecular biology
• Epigenetics
• Agricultural science

Background:

• De novo DNA methylation via the RNA-directed DNA methylation (RdDM) pathway is crucial for gene regulation and silencing transposable elements.
• CLASSY (CLSY) proteins are involved in recruiting RNA POLYMERASE IV (Pol IV) to initiate the RdDM pathway, but their specific roles in crops require further investigation.

Purpose of the Study:

• To investigate the role of OsCLSY4, a member of the CLSY family, in rice epigenomic regulation and its impact on agricultural traits.
• To elucidate the mechanism by which OsCLSY4 influences DNA methylation patterns and gene expression.

Main Methods:

• Epigenomics analyses to assess Pol IV-dependent small interfering RNA (siRNA) clusters and differentially methylated regions (DMRs).
• Analysis of gene expression (MADS22, GA20ox1) and DNA methylation changes in osclsy4 mutants.
• SunTag-mediated targeted demethylation to confirm the link between DNA methylation and gene expression.

Main Results:

• OsCLSY4 is identified as the dominant regulator of Pol IV-mediated epigenomic patterns in rice, controlling over 95% of Pol IV-dependent 24-nt siRNA clusters and over 70% of Pol IV-dependent hypomethylated CHH DMRs, primarily at miniature inverted-repeat transposable elements (MITEs).
• Loss of OsCLSY4 function leads to dysregulation of MADS22 and GA20ox1, impacting grain size through epigenetic modifications.
• OsCLSY4 exhibits tissue-specific methylation patterns in panicle and seedling and interacts with Pol IV, indicating its central role in the RdDM pathway.

Conclusions:

• OsCLSY4 acts as a central hub for Pol IV-mediated epigenomic regulation in rice, influencing gene silencing and agricultural traits.
• The findings suggest OsCLSY4's potential application in developing novel epigenetic breeding strategies for crop improvement.