24-nt reproductive phasiRNAs are broadly present in angiosperms.

Area of Science:

• Plant Molecular Biology
• Epigenetics and Small RNA Biology
• Plant Reproductive Development

Background:

• Small RNAs regulate plant growth and development.
• Phased small interfering RNAs (phasiRNAs) are a subclass requiring a trigger microRNA for biogenesis.
• In grasses, specific microRNAs trigger distinct phasiRNA pathways during anther development.

Purpose of the Study:

• To investigate the evolutionary presence and origin of the 24-nt phasiRNA pathway in flowering plants.
• To understand the role of the miR2275-triggered 24-nt phasiRNA pathway in reproductive development.
• To explore the evolutionary dynamics of this pathway across different plant lineages.

Main Methods:

• Comparative genomic analyses across diverse flowering plant species.
• Deep sequencing and analysis of small RNA populations.
• Bioinformatic identification and characterization of phasiRNA loci and their triggers.

Main Results:

• The miR2275-triggered 24-nt phasiRNA pathway is widely conserved in eudicots, suggesting its origin with anther emergence.
• This pathway is absent in legumes and Arabidopsis, indicating a dynamic evolutionary trajectory.
• In Solanaceae, 24-nt phasiRNAs are present but lack the miR2275 trigger, with some loci showing 12-nt phasing; both pathways are enriched during meiosis.

Conclusions:

• The 24-nt phasiRNA pathway, triggered by miR2275, is an ancient mechanism likely involved in anther and pollen development across angiosperms.
• The evolutionary history of this pathway is complex, with significant losses and modifications observed in certain lineages.
• The conserved spatiotemporal expression pattern of these phasiRNAs during meiotic stages highlights their critical role in reproductive success.