Relationship between reduction in rice (Nipponbare) leaf blade size under elevated CO₂ and miR396-GRF module

Area of Science:

• Plant Biology
• Molecular Biology
• Agricultural Science

Background:

• Elevated carbon dioxide (eCO2) affects plant development, including rice leaf morphology, leading to reduced leaf blade size compared to ambient CO2 (aCO2).
• MicroRNAs (miRNAs) are critical regulators of plant development, and their role in modulating leaf size under eCO2 is not fully understood.

Purpose of the Study:

• To identify specific miRNAs involved in regulating rice leaf size under eCO2 conditions.
• To elucidate the molecular mechanism by which eCO2 influences leaf development through miRNA pathways.

Main Methods:

• Small RNA sequencing (small RNA-seq) was employed to profile miRNA expression in developing rice leaves under eCO2 and aCO2.
• Quantitative analysis identified differentially expressed miRNAs, focusing on those with significant changes between conditions.
• Antisense oligonucleotide approach was used to validate the function of specific miRNAs and their target genes.

Main Results:

• Eighteen mature miRNA sequences showed expression changes greater than two-fold under eCO2.
• miR396e and miR396f expression levels were significantly altered by eCO2.
• Expression of growth-regulating factors (GRFs), potential targets of miR396s, was repressed under eCO2.
• Downregulation of GRF expression using an antisense oligonucleotide targeting miR396e mimicked the eCO2-induced reduction in leaf blade length.

Conclusions:

• The miR396-GRF module plays a crucial role in controlling rice leaf blade length under elevated CO2 environments.
• This study reveals a specific miRNA-mediated mechanism underlying plant morphological responses to increased atmospheric CO2.