Developmentally regulated expression and complex processing of barley pri-microRNAs.

Area of Science:

• Plant molecular biology
• Genomics
• Gene regulation

Background:

• MicroRNAs (miRNAs) are crucial regulators of gene expression.
• Barley, an economically important cereal, has limited data on miRNA biogenesis.
• Existing databases lack experimental data on barley pri-miRNA and MIR gene structures.

Purpose of the Study:

• To investigate the structural organization of barley microRNA genes.
• To examine the biogenesis of selected barley miRNAs.
• To understand the developmental regulation of pri-miRNA processing for miRNA maturation.

Main Methods:

• Selection and analysis of nine barley microRNAs (e.g., miR156g, miR168a).
• Confirmation of miRNA presence using Northern blot analysis.
• Characterization of gene structures, including introns and splicing events.

Main Results:

• Barley miRNAs are encoded by genes with diverse organizations, often as independent transcription units with or without introns.
• Intron-containing miRNA transcripts exhibit complex splicing, generating various isoforms.
• miRNAs were identified within introns of noncoding genes (MIR156g, MIR1126) and within the 3' UTR of a protein-coding gene (miR1120).
• miR397b-3p was identified as a functional miRNA in barley, unlike in rice.
• Stable mature molecules were generated from both arms of MIR168a-5p/168a-3p, indicating evolutionary conservation.

Conclusions:

• Seven of eight characterized barley miRNA genes contain introns, with developmentally specific processing of their transcripts.
• Differential splicing efficiencies of introns encoding miR156g and miR1126 suggest regulatory mechanisms.
• These findings provide insights into miRNA maturation and regulation in barley.