Alteration of osa-miR156e expression affects rice plant architecture and strigolactones (SLs) pathway.

KEY MESSAGE: Overexpressing osa--miR156e in rice produced a bushy mutant and osa--miR156e regulation of tillering may do this through the strigolactones (SLs) pathway. Appropriate downregulation of osa--miR156 expression contributed to the improvement of plant architecture. Tillering is one of the main determinants for rice architecture and yield. In this study, a bushy mutant of rice was identified with increased tiller number, reduced plant height, prolonged heading date, low seed setting, and small panicle size due to a T-DNA insertion which essentially elevated the expression of osa-miR156e. Transgenic plants with constitutive expression of osa-miR156e also had the bushy phenotype, which showed osa-miR156 may control apical dominance and tiller outgrowth via regulating the strigolactones signaling pathway. Furthermore, the extent of impaired morphology was correlated with the expression level of osa-miR156e. In an attempt to genetically improve rice architecture, ectopic expression of osa-miR156e under the GAL4-UAS system or OsTB1 promoter was conducted. According to agronomic trait analysis, pTB1:osa-miR156e transgenic plants significantly improved the grain yield per plant compared to plants overexpressing osa-miR156e, even though the yield was still inferior to the wild type, making it a very interesting albeit negative result. Our results suggested that osa-miR156 could serve as a potential tool for modifying rice plant architecture through genetic manipulation of the osa-miR156 expression level.