MTS1 regulates rice plant architecture by mediating phosphoinositide metabolism

Plant architecture is an agronomically important trait affecting grain yield in rice (Oryza sativa L.). Here, we identified a gene, Moderate-tillering and Semi-dwarf 1 (MTS1), which encodes a type II Inositol polyphosphate 5-phosphatase (5PTase). Compared to the wild type, the mts1 mutant exhibited a significant reduction in plant height and an increase in effective tiller number. Further analysis showed that the mutation in MTS1 impairs the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], resulting in its aberrant accumulation and subsequent suppression of actin polymerization. Notably, the mutation in MTS1 specifically affects the response to gibberellin at the reproductive growth stage. Both lipid-protein overlay assay and microscale thermophoresis assay demonstrated that phosphatidylinositol 4-phosphate (PI4P) interacts with NGR5. PI4P promotes NGR5 degradation, thereby modulating plant architecture. Investigation of yield-related traits showed that the mts1 mutant has a similar grain yield per plant to the wild type due to the compensation effect of increasing effective tiller number. These findings suggest that phosphoinositide metabolism plays a critical role in modulating plant architecture in rice and the favourable allele of MTS1 has potential application value in rice dwarf breeding.