Rice RS2-9, which is bound by transcription factor OSH1, blocks enhancer-promoter interactions in plants

Area of Science:

• Plant molecular biology
• Genomics
• Epigenetics

Background:

• Insulators are critical for regulating gene expression by blocking enhancer-promoter interactions in animals.
• The function and characterization of insulators in plants remain largely unexplored due to a scarcity of identified insulators and their binding factors.
• Understanding plant insulators is key to deciphering genome organization and gene regulation.

Purpose of the Study:

• To characterize a novel plant insulator and its associated binding factor.
• To investigate the role of this insulator in gene regulation and genome topology in plants.
• To establish a functional plant insulator system for future genetic studies.

Main Methods:

• Isolation and characterization of the RS2-9 insulator from the Oryza sativa (rice) genome.
• Testing insulator activity in transgenic Arabidopsis and Nicotiana tabacum by interposing RS2-9 between enhancers and promoters.
• Identifying and mutating binding sites for the O. sativa Homeobox 1 (OSH1) protein within the RS2-9 insulator.
• Analyzing histone modifications and transcriptional interactions of genes flanking the RS2-9 insulator in rice.
• Mapping OSH1 binding sites genome-wide and correlating them with topologically associated domain (TAD) boundaries.

Main Results:

• The isolated RS2-9 insulator effectively blocked both constitutive and floral organ-specific enhancers in transgenic plants.
• The OSH1 protein was identified as a binding factor for RS2-9, with mutations in OSH1 binding sites significantly impairing insulation.
• OSH1 binding sites were found to be enriched at the boundaries of topologically associated domains (TADs) in the rice genome.
• Genes flanking RS2-9 in the rice genome showed no mutual transcriptional interactions or spread of histone modifications.

Conclusions:

• The OSH1-RS2-9 complex functions as a true insulator in plants, regulating gene expression and genome topology.
• OSH1 plays a significant role in gene insulation and the organization of the plant genome.
• This study provides a valuable tool and insights into the mechanisms of genome regulation in plants.