Serrate-Associated Protein 1, a splicing-related protein, promotes miRNA biogenesis in Arabidopsis

Area of Science:

• Plant molecular biology
• Gene regulation
• MicroRNA biogenesis

Background:

• MicroRNAs (miRNAs) are key gene expression regulators in plants, processed from primary miRNA transcripts (pri-miRNAs) by the Dicer-like 1 (DCL1) complex.
• Serrate-Associated Protein 1 (SEAP1), a conserved splicing protein, has known roles in humans and yeast, but its function in plants was unknown.

Purpose of the Study:

• To investigate the function of Serrate-Associated Protein 1 (SEAP1) in plant development and microRNA (miRNA) biogenesis.
• To elucidate the molecular mechanisms by which SEAP1 influences miRNA production and gene expression.

Main Methods:

• Analysis of SEAP1 function using genetic approaches, including SEAP1 knockout and knockdown (amiR^SEAP1) in plants.
• Biochemical assays to determine SEAP1's association with the DCL1 complex.
• Quantitative analysis of pri-miRNA and mature miRNA levels.
• Global analysis of pri-miRNA splicing and mRNA intron retention.

Main Results:

• Loss of SEAP1 function leads to embryo lethality, while its knockdown causes developmental defects and reduced miRNA accumulation.
• SEAP1 physically associates with the DCL1 complex, potentially facilitating its interaction with pri-miRNAs.
• SEAP1 enhances pri-miRNA accumulation without affecting transcription, suggesting a role in pri-miRNA stabilization.
• SEAP1 influences pri-miRNA splicing and global mRNA intron retention, indicating a broader role in RNA processing.

Conclusions:

• SEAP1 plays essential roles in plant development and miRNA biogenesis, extending beyond its known splicing functions.
• SEAP1 promotes miRNA production by enhancing pri-miRNA stability and processing, and potentially by modulating pri-miRNA splicing.
• These findings highlight conserved and novel functions of SEAP1 in plants, impacting both miRNA pathways and general RNA metabolism.