DH2-dependent trans-acting siRNAs regulate leaf and lemma development in rice

Area of Science:

• Plant Molecular Biology
• Plant Development
• Genetics

Background:

• Lateral organ development, including leaves and floral organs, is crucial for plant architecture and yield.
• Establishing polarity in lateral organs is essential for their morphogenesis, but molecular mechanisms in rice are not fully understood.
• Previous studies in *Arabidopsis* suggest ARGONAUT 7 (AGO7) plays a role in lateral organ development.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying lateral organ polarity establishment in rice.
• To investigate the function of the ARGONAUT 7 (AGO7) gene in rice development.
• To characterize the role of the OsAGO7-tasiR-ARFs pathway in lemma development.

Main Methods:

• Isolation and characterization of two allelic rice mutants, *degenerated hull 2* (*dh2-1* and *dh2-2*).
• Gene expression analysis using quantitative real-time PCR and *in situ* hybridization.
• Analysis of mutant phenotypes, including leaf rolling and lemma morphology.

Main Results:

• Mutants *dh2-1* and *dh2-2* exhibited abaxially rolled leaves and rod-shaped lemmas, indicating defects in lateral organ polarity.
• DH2 encodes ARGONAUT 7 (AGO7), a protein expressed in lateral organs.
• The OsAGO7-tasiR-ARFs pathway was found to be involved in restricting ectopic expression of *OsARF* genes (specifically *OsARF2, OsARF3, OsARF14*, and *OsARF15*) in the lemma, influencing overall lemma development rather than just adaxial-abaxial polarity.

Conclusions:

• The OsAGO7-tasiR-ARFs pathway plays a significant role in rice lemma development.
• This pathway functions by regulating the expression of *OsARF* genes across the entire lemma, not solely in the adaxial-abaxial axis.
• The mechanism differs from that observed in *Arabidopsis*, highlighting species-specific regulation of lateral organ development.