Vv-circSIZ1 mediated by pre-mRNA processing machinery contributes to salt tolerance

Area of Science:

• Plant molecular biology
• Epigenetics
• Biochemistry

Background:

• Circular RNAs (circRNAs) are prevalent in plants, yet their biogenesis and functional roles are poorly understood.
• Understanding circRNA regulation is key to advancing plant science and crop improvement.

Purpose of the Study:

• To investigate the biogenesis and anti-salt functions of a novel grape circRNA, Vv-circSIZ1.
• To elucidate the regulatory mechanisms governing Vv-circSIZ1 expression and activity.

Main Methods:

• Extensive mutagenesis of expression plasmids and genetic transformation.
• Analysis of circRNA expression in different plant species (grape, *Nicotiana benthamiana*, *Arabidopsis*).
• Investigating the role of flanking introns, splicing signals, spliceosome activity, and RNA-binding proteins in circRNA biogenesis.

Main Results:

• Identified Vv-circSIZ1, primarily expressed in grape xylem cytoplasm, with species-specific characteristics.
• Demonstrated a positive correlation between flanking intron retention length and Vv-circSIZ1 generation efficiency.
• Showed that spliceosome activity is inversely proportional to Vv-circSIZ1 expression and that RNA-binding proteins regulate its expression.
• Overexpression of Vv-circSIZ1 enhanced salt tolerance in grape and *N. benthamiana*.
• Vv-circSIZ1 alleviates VvmiR3631-mediated repression of VvVHAc1 and promotes parental gene transcription.

Conclusions:

• Elucidated the biogenesis mechanism of Vv-circSIZ1, emphasizing the role of flanking introns and splicing signals.
• Established Vv-circSIZ1 as a functional circRNA that confers salt tolerance.
• Revealed Vv-circSIZ1's regulatory roles in miRNA pathways and gene transcription, expanding the understanding of circRNAs in plants.