Blocking miR528 function promotes tillering and regrowth in switchgrass

Area of Science:

• Plant molecular biology
• Genetics
• Biotechnology

Background:

• MicroRNAs (miRNAs) are crucial regulators of biological processes in plants.
• The function of miRNAs in switchgrass (Panicum virgatum), a key biofuel and forage crop, remains largely unexplored.
• miR528 is present in four copies in switchgrass.

Purpose of the Study:

• To elucidate the function of miR528 in switchgrass.
• To investigate the role of miR528 in controlling biomass traits, specifically tillering and regrowth.
• To identify miR528 targets involved in biomass regulation.

Main Methods:

• Expression of short tandem target mimic (STTM) to block miR528 activity.
• Generation and analysis of quadruple pvmir528 mutant lines using genome editing.
• Degradome sequencing and RNA sequencing (RNA-seq) to identify targets.
• In situ hybridization to determine target localization.

Main Results:

• Blocking miR528 activity or creating pvmir528 mutants enhanced tiller number and regrowth rate after mowing.
• Up-regulation of two miR528 target genes encoding Cu/Zn-SOD enzymes was observed in mutants.
• Natural variations in the miR528-SOD interaction were found across monocot species.

Conclusions:

• miR528 plays a novel role in regulating switchgrass biomass traits.
• The miR528-Cu/Zn-SOD module is a potential target for genetic manipulation to improve crop biomass.
• Distinct regulatory roles of this module evolved during monocot diversification.